ORCID Profile
0000-0003-0476-0237
Current Organisation
RMIT University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Artificial Intelligence and Image Processing | Environmental and Occupational Health and Safety | Nanotoxicology, Health and Safety | Simulation and Modelling | Microfluidics and nanofluidics | Building Not Elsewhere Classified | Tissue engineering | Additive manufacturing | Manufacturing engineering | Simulation And Modelling | Public Health and Health Services | Environmental And Occupational Health And Safety | Evolutionary Biology | Composite and hybrid materials | Biofabrication | Biomedical engineering | Conservation and Biodiversity | Behavioural Ecology | Biological Adaptation
ANZSRC Socio-Economic Objective (SEO)
Urban and Industrial Air Quality | Respiratory System and Diseases (incl. Asthma) | Occupational Health | Application packages | Occupational health (excl. economic development aspects) | Flora, Fauna and Biodiversity of environments not elsewhere classified | Air Quality not elsewhere classified | Environmental health | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Improving predictions of heat transfer in indoor environments with eddy viscosity turbulence models
Publisher: Springer Science and Business Media LLC
Date: 24-11-2016
Micron particle deposition in a tracheobronchial airway model under different breathing conditions
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.MEDENGPHY.2010.08.012
Abstract: Effective management of asthma is dependent on achieving adequate delivery of the drugs into the lung. Inhalers come in the form of dry powder inhalers (DPIs) and metered dose inhalers (pMDIs) with the former requiring a deep fast breath for activation while there are no restrictions on inhalation rates for the latter. This study investigates two aerosol medication delivery methods (i) an idealised case for drug particle delivery under a normal breathing cycle (inhalation-exhalation) and (ii) for an increased effort during the inhalation with a breath hold. A computational model of a human tracheobronchial airway was reconstructed from computerised tomography (CT) scans. The model's geometry and lobar flow distribution were compared with experimental and empirical models to verify the current model. Velocity contours and secondary flow vectors showed vortex formation downstream of the bifurcations which enhanced particle deposition. The velocity contour profiles served as a predictive tool for the final deposition patterns. Different spherical aerosol particle sizes (3-10μm, 1.55g/cm(3)) were introduced into the airway for comparison over a range of Stokes number. It was found that a deep inhalation with a breath hold of 2s did not necessarily increase later deposition up to the sixth branch generation, but rather there was an increase in the deposition in the first few airway generations was found. In addition the breath hold allows deposition by sedimentation which assists in locally targeted deposition. Visualisation of particle deposition showed local "hot-spots" where particle deposition was concentrated in the lung airway.
Enhancing respiratory comfort with fan respirators: Computational analysis of carbon dioxide reduction, temperature regulation, and humidity control
Publisher: AIP Publishing
Date: 05-2023
DOI: 10.1063/5.0146710
Abstract: Respirators provide protection from inhalation exposure to dangerous substances, such as chemicals and infectious particles, including SARS-COVID-laden droplets and aerosols. However, they are prone to exposure to stale air as masks create a microclimate influenced by the exhaled air. As a result, exhaled air from lungs accumulating in the mask produces a warm and humid environment that has a high concentration of carbon dioxide (CO2), unsuitable for re-inhalation. Fans are a favorable option for respirators to ventilate the mask and remove the stale air. This study utilized computational fluid dynamics simulation consisting of a hybrid Reynolds-averaged Navier–Stokes-large eddy simulation turbulence method to compare the inhalation flow properties for different fan locations (bottom, top, and side) with regular respirator breathing. Three mask positions, top, side, and bottom, were evaluated under two breathing cycles (approximately 9.65 s of breathing time). The results demonstrated that adding a fan respirator significantly decreased internal mask temperature, humidity, and CO2 concentration. The average CO2 concentration decreased by 87%, 67%, and 73% for locations bottom, top, and side, respectively. While the top and side fan locations enhanced the removal of the exhaled gas mixture, the bottom-fan respirator was more efficient in removing the nostril jet gas mixture and therefore provided the least barrier to respiratory function. The results provide valuable insight into the benefits of fan respirators for long-term use for reducing CO2 concentration, mask temperature, and humidity, improving wearer safety and comfort in hazardous environments, especially during the COVID-19 pandemic.
Numerical Comparison of Nasal Aerosol Administration Systems for Efficient Nose-to-Brain Drug Delivery
Publisher: Springer Science and Business Media LLC
Date: 29-12-2018
DOI: 10.1007/S11095-017-2280-6
Abstract: Nose-to-brain drug administration along the olfactory and trigeminal nerve pathways offers an alternative route for the treatment of central nervous system (CNS) disorders. The characterization of particle deposition remains difficult to achieve in experiments. Alternative numerical approach is applied to identify suitable aerosol particle size with maximized inhaled doses. This study numerically compared the drug delivery efficiency in a realistic human nasal cavity between two aerosol drug administration systems targeting the olfactory region: the aerosol mask system and the breath-powered bi-directional system. Steady inhalation and exhalation flow rates were applied to both delivery systems. The discrete phase particle tracking method was employed to capture the aerosol drug transport and deposition behaviours in the nasal cavity. Both overall and regional deposition characteristics were analysed in detail. The results demonstrated the breath-powered drug delivery approach can produce superior olfactory deposition with peaking olfactory deposition fractions for diffusive 1 nm particles and inertial 10 μm. While for particles in the range of 10 nm to 2 μm, no significant olfactory deposition can be found, indicating the therapeutic agents should avoid this size range when targeting the olfactory deposition. The breath-powered bi-directional aerosol delivery approach shows better drug delivery performance globally and locally, and improved drug administration doses can be achieved in targeted olfactory region.
Nasal sprayed particle deposition in a human nasal cavity under different inhalation conditions
Publisher: Public Library of Science (PLoS)
Date: 06-09-2019
Primary spray breakup from a nasal spray atomizer using volume of fluid to discrete phase model
Publisher: AIP Publishing
Date: 05-2023
DOI: 10.1063/5.0150890
Abstract: Spray atomization process involves complex multi-phase phenomena. Abundant literature and validation of spray modeling for industrial applications like fuel injection in internal combustion and turbine jet engines are available. However, only a handful of studies, primarily limited to discrete phase modeling, of low-pressure applications, such as nasal spray exists. This study aims to provide insight into the external and near-nozzle spray characterization of a continuous spray and establishes good validation against the experiment. A three-dimensional (3D) x-ray scanner was used to extract the internal nasal spray nozzle geometry which was reconstructed to build a 3D computational model. A novel volume-of-fluid to discrete phase transition model was used to track the liquid phase and its transition to droplets, which was based on the shape and size of the liquid lumps. In this study, an early pre-stable and stable phase of spray plume development was investigated. Qualitative and quantitative analyses were carried out to validate the computational model. A liquid column exited a nozzle which distorted at its base with advancement in time and eventually formed a hollow-cone liquid sheet. It then disintegrated due to instability that produced fluctuations to form ligaments resulting in secondary breakup. This study provides in-depth understanding of liquid jet disintegration and droplet formation, which adds value to future nasal spray device designs and techniques to facilitate more effective targeted nasal drug delivery.
Nonlinear eddy viscosity modeling and experimental study of jet spreading rates
Publisher: Hindawi Limited
Date: 13-06-2014
DOI: 10.1111/INA.12050
Abstract: Indoor airflow pattern is strongly influenced by turbulent shear and turbulent normal stresses that are responsible for entrainment effects and turbulence-driven secondary motion. Therefore, an accurate prediction of room airflows requires reliable modeling of these turbulent quantities. The most widely used turbulence models include RANS-based models that provide quick solutions but are known to fail in turbulent free shear and wall-affected flows. In order to cope with this deficiency, this study presents a nonlinear k-ε turbulence model and evaluates it along with linear k-ε models for an indoor isothermal linear diffuser jet flow measured in two model rooms using PIV. The results show that the flow contains a free jet near the inlet region and a wall-affected region downstream where the jet is pushed toward the ceiling by entrainment through the well-known Coanda effect. The CFD results show that an accurate prediction of the entrainment process is very important and that the nonlinear eddy viscosity model is able to predict the turbulence-driven secondary motions. Furthermore, turbulence models that are calibrated for high Reynolds free shear layer flows were not able to reproduce the measured velocity distributions, and it is suggested that the model constants of turbulence models should be adjusted before they are used for room airflow simulations.
Computational investigation of nasal surface coverage from squeeze bottle and Neti Pot saline irrigation flow
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.CMPB.2022.107223
Abstract: Nasal saline irrigation is a common therapy for inflammatory nasal and paranasal disease or for managing post nasal and sinus surgery recovery. Two common irrigation devices include the netipot and squeeze bottles, where anecdotally, these devices alleviate congestion, facial pain, and pressure. However, a quantitative evaluation of these devices' performance and the fluid dynamics responsible for the irrigation distribution through the nose is lacking. This study tracked the liquid surface coverage and wall shear stresses during nasal saline irrigation produced from a Neti Pot and squeeze bottle. This study used transient computational fluid dynamics (CFD) simulations to investigate the saline irrigation flow field in a subject-specific sinonasal model. The computational nasal cavity model was constructed from a high-resolution computed tomography scan (CT). The irrigation procedure applied a head position tilted at 90° forward using an 80 ml squeeze bottle and 120 ml Neti Pot. The results from a single sinonasal model demonstrated that the Neti Pot irrigation was more effective in delivering saline solution to the nasal cavity on the contralateral side of irrigation due to typically larger volumes but at the expense of reduced flow and shearing rates, as the flow entered under gravitational forces. The squeeze bottle irrigation provided greater surface coverage on the side of irrigation. The results from the single patient model, demonstrated the Neti Pot increased surface coverage in the paranasal sinuses. Reducing the jet diameter may aid the direct targeting of a specific region at the side of irrigation by preventing the impingement of the jet to the nasal passage surface and redirection of the flow. Evaluating this performance across a wider cohort of patients can strengthen the findings.
Examining mesh independence for flow dynamics in the human nasal cavity
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.COMPBIOMED.2018.09.010
Abstract: Increased computational resources provide new opportunities to explore sophisticated respiratory modelling. A survey of recent publications showed a steady increase in the number of mesh elements used in computational models over time. Complex geometries such as the nasal cavity exhibit sharp gradients and irregular curvatures, leading to abnormal flow development across their surfaces. As such, a robust method for examining the near-wall mesh resolution is required. The non-dimensional wall unit y
Numerical study of the effects of human body heat on particle transport and inhalation in indoor environment
Publisher: Elsevier BV
Date: 2013
Modelling the effects of post-FESS middle turbinate synechiae on sinonasal physiology: A computational fluid dynamics study
Publisher: Elsevier BV
Date: 12-2023
Targeted drug delivery with polydisperse particle transport and deposition in patient-specific upper airway during inhalation and exhalation
Publisher: Elsevier BV
Date: 02-2023
DOI: 10.1016/J.RESP.2022.103986
Abstract: Identifying the deposition pattern of inhaled pharmaceutical aerosols in the human respiratory system and understanding the effective parameters in this process is vital for more efficient drug delivery to this region. This study investigated aerosol deposition in a patient-specific upper respiratory airway and determined the deposition fraction (DF) and pressure drop across the airway. An experimental setup was developed to measure the pressure drop in the same realistic geometry printed from the patient-specific geometry. The unsteady simulations were performed with a flow rate of 15L/min and different particle diameters ranging from 2 to 30µm. The results revealed significant flow circulation after the nasal valve in the upper and oropharynx regions, and a maximum local velocity observed in the nasopharynx. Transient cumulative deposition fraction showed that after 2s of the simulation, all particles deposit or escape the computational domain. About 30% of the injected large particles (d
A numerical investigation of wind environment around a walking human body
Publisher: Elsevier BV
Date: 09-2017
Lagrangian particle modelling of spherical nanoparticle dispersion and deposition in confined flows
Publisher: Elsevier BV
Date: 06-2016
Comparison of micron- and nanoparticle deposition patterns in a realistic human nasal cavity
Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.RESP.2009.02.014
Abstract: Knowledge regarding particle deposition processes in the nasal cavity is important in aerosol therapy and inhalation toxicology applications. This paper presents a comparative study of the deposition of micron and submicron particles under different steady laminar flow rates using a Lagrangian approach. A computational model of a nasal cavity geometry was developed from CT scans and the simulation of the fluid and particle flow within the airway was performed using the commercial software GAMBIT and FLUENT. The air flow patterns in the nasal cavities and the detailed local deposition patterns of micron and submicron particles were presented and discussed. It was found that the majority of micron particles are deposited near the nasal valve region and some micron particles are deposited on the septum wall in the turbinate region. The deposition patterns of micron particles in the left cavity are different compared with that in the right one especially in the turbinate regions. In contrast, the deposition for nanoparticles shows a moderately even distribution of particles throughout the airway. Furthermore the particles releasing position obviously influences the local deposition patterns. The influence of the particle releasing position is mainly shown near the nasal valve region for micron particle deposition, while for submicron particles deposition, both the nasal valve and turbinate region are influenced. The results of the paper are valuable in aerosol therapy and inhalation toxicology.
External Characteristics of Unsteady Spray Atomization from a Nasal Spray Device
Publisher: Elsevier BV
Date: 03-2013
DOI: 10.1002/JPS.23449
Numerical investigation of micron particle inhalation by standing thermal manikins in horizontal airflows
Publisher: SAGE Publications
Date: 11-09-2014
Abstract: Computational fluid dynamics computations were conducted to investigate the particle inhalation characteristics of a thermal manikin standing in a horizontal airflow with different orientations, leg postures, wind speeds and particle sizes. The computations revealed that only when the manikin’s thermal plume moves into the breathing zone (namely, the manikin is facing the lee side) could the body heat affect the characteristics of particle inhalation. Further computations demonstrated that, when facing the lee side, the manikin’s particle inhalation is highly sensitive to its leg posture. When the legs are separated, air can flow through the gap, causing more particle entrainment into the breathing zone from the lower level. Although the thermal effect of body heat is gradually suppressed with increasing wind speed or particle size, different leg postures have different environmental sensitivities.
A combined experimental and numerical study on upper airway dosimetry of inhaled nanoparticles from an electrical discharge machine shop
Publisher: Springer Science and Business Media LLC
Date: 12-07-2017
Ultra-sensitive photoelectrochemical aptamer biosensor for detecting E. coli O157:H7 based on nonmetallic plasmonic two-dimensional hydrated defective tungsten oxide nanosheets coupling with nitrogen-doped graphene quantum dots (dWO3•H2O@N-GQDs)
Publisher: Elsevier BV
Date: 07-2021
Air conditioning analysis among human nasal passages with anterior anatomical variations
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.MEDENGPHY.2018.04.010
Abstract: A major functional role of the nasal cavity is air conditioning of the inspired environmental air to near alveolar conditions. It is well known that the anatomical disparities among nasal passages can change airflow patterns to a great extent. However, its effect on nasal air conditioning performance remains largely unexplored. This research investigated the nasal air conditioning performance among nasal models with distinct vestibule phenotypes, including subjects with and without vestibule notches. For the mass transfer, we used a two-film theory model to determine the species transport. Airflow patterns, heat and mass transfer between the inhaled airflow and the nasal mucosa were analysed and compared. Results showed that the nasal air conditioning performance is closely related to nasal passage structures. The anatomical variations, especially the geometry changes in the anterior vestibule region, can increase both heat and mass transfer rate between nasal mucous and respiratory air at the vicinity of the notched regions, while for other regions such as the anterior superior nasal cavity, the heat transfer is greatly reduced to even zero heat flux due to lack of active airflow passing.
Numerical simulations of the flow and aerosol dispersion in a violent expiratory event: Outcomes of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events”
Publisher: AIP Publishing
Date: 04-2023
DOI: 10.1063/5.0143795
Abstract: This paper presents and discusses the results of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events” aimed at assessing the ability of different computational codes and turbulence models to reproduce the flow generated by a rapid prototypical exhalation and the dispersion of the aerosol cloud it produces. Given a common flow configuration, a total of 7 research teams from different countries have performed a total of 11 numerical simulations of the flow dispersion by solving the Unsteady Reynolds Averaged Navier–Stokes (URANS) or using the Large-Eddy Simulations (LES) or hybrid (URANS-LES) techniques. The results of each team have been compared with each other and assessed against a Direct Numerical Simulation (DNS) of the exact same flow. The DNS results are used as reference solution to determine the deviation of each modeling approach. The dispersion of both evaporative and non-evaporative particle clouds has been considered in 12 simulations using URANS and LES. Most of the models predict reasonably well the shape and the horizontal and vertical ranges of the buoyant thermal cloud generated by the warm exhalation into an initially quiescent colder ambient. However, the vertical turbulent mixing is generally underpredicted, especially by the URANS-based simulations, independently of the specific turbulence model used (and only to a lesser extent by LES). In comparison to DNS, both approaches are found to overpredict the horizontal range covered by the small particle cloud that tends to remain afloat within the thermal cloud well after the flow injection has ceased.
Transport and Deposition of Welding Fume Agglomerates in a Realistic Human Nasal Airway
Publisher: Oxford University Press (OUP)
Date: 13-04-2016
Abstract: Welding fume is a complex mixture containing ultra-fine particles in the nanometer range. Rather than being in the form of a singular sphere, due to the high particle concentration, welding fume particles agglomerate into long straight chains, branches, or other forms of compact shapes. Understanding the transport and deposition of these nano-agglomerates in human respiratory systems is of great interest as welding fumes are a known health hazard. The neurotoxin manganese (Mn) is a common element in welding fumes. Particulate Mn, either as soluble salts or oxides, that has deposited on the olfactory mucosa in human nasal airway is transported along the olfactory nerve to the olfactory bulb within the brain. If this Mn is further transported to the basal ganglia of the brain, it could accumulate at the part of the brain that is the focal point of its neurotoxicity. Accounting for various dynamic shape factors due to particle agglomeration, the current computational study is focused on the exposure route, the deposition pattern, and the deposition efficiency of the inhaled welding fume particles in a realistic human nasal cavity. Particular attention is given to the deposition pattern and deposition efficiency of inhaled welding fume agglomerates in the nasal olfactory region. For particles in the nanoscale, molecular diffusion is the dominant transport mechanism. Therefore, Brownian diffusion, hydrodynamic drag, Saffman lift force, and gravitational force are included in the model study. The deposition efficiencies for single spherical particles, two kinds of agglomerates of primary particles, two-dimensional planar and straight chains, are investigated for a range of primary particle sizes and a range of number of primary particles per agglomerate. A small fraction of the inhaled welding fume agglomerates is deposited on the olfactory mucosa, approximately in the range 0.1-1%, and depends on particle size and morphology. The strong size dependence of the deposition in olfactory mucosa on particle size implies that the occupation deposition of welding fume manganese can be expected to vary with welding method.
Correlation of regional deposition dosage for inhaled nanoparticles in human and rat olfactory
Publisher: Springer Science and Business Media LLC
Date: 25-01-2019
Source and trajectories of inhaled particles from a surrounding environment and its deposition in the respiratory airway
Publisher: Informa UK Limited
Date: 04-2013
DOI: 10.3109/08958378.2013.781250
Abstract: The inhalation exposure to airborne particles is investigated using a newly developed computational model that integrates the human respiratory airway with a human mannequin and at an enclosed room environment. Three free-stream air flow velocities (0.05, 0.20, and 0.35 m s⁻¹) that are in the range of occupational environments are used. Particles are released from different upstream locations and their trajectories are shown, which revealed that the trajectory paths of 80 μm particles that are inhaled are the same from the three different upstream planes evaluated. Smaller particles, 1 and 10 μm, exhibited different inhalation paths when released from different upstream distances. The free-stream velocity also has an effect on the particle trajectory particularly for larger particles. The aspiration efficiency for an extended range of particle sizes was evaluated. Reverse particle tracking matches the deposition in the respiratory airway with its initial particle source location. This can allow better risk assessments, and dosimetry determination due to inhalation exposure to contaminant sources.
Numerical investigation of particle transport and inhalation using standing thermal manikins
Publisher: Elsevier BV
Date: 02-2013
Micron particle deposition in the nasal cavity using the v2-f model
Publisher: Elsevier BV
Date: 12-2011
Numerical air conditioning performance assessment of nasal models with morphologic variations
Publisher: IEEE
Date: 04-2017
Experimental visualisation of wake flows induced by different shaped moving manikins
Publisher: Elsevier BV
Date: 09-2018
Detailed nanoparticle exposure analysis among human nasal cavities with distinct vestibule phenotypes
Publisher: Elsevier BV
Date: 07-2018
Inhalation of toxic and therapeutic particles in a human nasal cavity
Publisher: IEEE
Date: 05-2008
Inhalation exposure analysis of lung-inhalable particles in an approximate rat central airway
Publisher: MDPI AG
Date: 18-07-2019
Abstract: Rats have been widely used as surrogates for evaluating the adverse health effects of inhaled airborne particulate matter. This paper presents a computational fluid and particle dynamics (CFPD) study of particle transport and deposition in an approximate rat central airway model. The geometric model was constructed based on magnetic resonance (MR) imaging data sourced from previous study. Lung-inhalable particles covering a diameter range from 20 nm to 1.0 µm were passively released into the trachea, and the Lagrangian particle tracking approach was used to predict in idual particle trajectories. Overall, regional and local deposition patterns in the central airway were analyzed in detail. A preliminary interspecies data comparison was made between present rat models and previously published human data. Results showed deposition “hot spots” were mainly concentrated at airway bifurcation apexes, and a gravitational effect should also be considered for inertia particles when using a rat as a laboratory animal. While for humans, this may not happen as the standing posture is completely different. Lastly, the preliminary interspecies data comparison confirms the deposition similarity in terms of deposition enhancement factors, which is a weighted deposition concentration parameter. This interspecies comparison confirms feasibility of extrapolating surrogate rat deposition data to humans using existing data extrapolation approach, which mostly relies on bulk anatomical differences as dose adjustment factors.
Computational fluid and particle dynamics in the human respiratory system
Publisher: Springer Netherlands
Date: 2012
Measurements of droplet size distribution and analysis of nasal spray atomization from different actuation pressure
Publisher: Mary Ann Liebert Inc
Date: 02-2015
Abstract: To evaluate the deposition efficiency of spray droplets in a nasal cavity produced from a spray device, it is important to determine droplet size distribution, velocity, and its dispersion during atomization. Due to the limiting geometric dimensions of the nasal cavity airway, the spray plume cannot develop to its full size inside the nasal vestibule to penetrate the nasal valve region for effective drug deposition. Particle/droplet image analysis was used to determine local mean droplet sizes at eight regions within the spray plume under different actuation pressures that represent typical hand operation from pediatric to adult patients. The results showed that higher actuation pressure produces smaller droplets in the atomization. Stronger actuation pressure typical of adult users produces a longer period of the fully atomized spray stage, despite a shorter overall spray duration. This produces finer droplets when compared with the data obtained by weaker actuation pressure, typical of pediatric users. The experimental technique presented is able to capture a more complete representation of the droplet size distribution and the atomization process during an actuation. The measured droplet size distribution produced can be related to the empirically defined deposition efficiency curve of the nasal cavity, allowing a prediction of the likely deposition.
Effect of breathing profiles on nebuliser drug delivery targeting the paranasal sinuses in a post-operative nasal cavity
Publisher: Elsevier BV
Date: 03-2022
Characterization of nasal irrigation flow from a squeeze bottle using computational fluid dynamics
Publisher: Wiley
Date: 06-11-2020
DOI: 10.1002/ALR.22476
Abstract: Nasal saline irrigation has become standard of care in various sinonasal conditions, including allergic and nonallergic rhinitis, chronic rhinosinusitis, and in the postoperative patient. Evidence regarding the mechanisms and dynamics of liquid flow through the sinonasal cavity remains limited due to inadequate experimental models (cadaveric, 3-dimensional [3D] printed, imaging of labeled dyes and radioisotopes). We aimed to develop a computational fluid dynamics (CFD) model of nasal irrigation to demonstrate sinonasal surface coverage, residence times across the mucosal surfaces, and shearing force of irrigation. A nasal cavity geometry derived from high-resolution paranasal sinus computed tomography (CT) scans of a healthy, unoperated, 25-year-old patient was created. CFD analysis was performed to assess the distribution of nasal irrigation from a tapered nozzle bottle at a forward head-tilt position of 45 degrees with a 2-second burst at 35 mL/second. The model demonstrates nasal irrigation from ipsilateral to contralateral with precise measures of velocity, pressure, wall shear stress, and mapping of surface coverage and residence times at specific locations and times. The nasal cavity experiences almost complete coverage of irrigation, while overflow from the nasal cavity facilitates moderate coverage of the ipsilateral maxillary (40%) and anterior ethmoid sinuses (30%). Negligible coverage of the sphenoid and frontal sinuses was noted. Detailed physical mechanisms of liquid irrigation injected from a commonly used squeeze bottle were shown. Ipsilateral maxillary and ethmoid sinus penetration are primarily due to overflow rather than direct jet entry, confirming the recommendation of larger volumes of irrigation to "flood" the sinus ostia.
Airway geometry and inhalation effort comparisons in a narrowed and recovered airway tree associated with acute asthma
Publisher: IEEE
Date: 07-2008
Detailed deposition analysis of inertial and diffusive particles in a rat nasal passage
Publisher: Informa UK Limited
Date: 02-01-2018
DOI: 10.1080/08958378.2018.1439549
Abstract: Rats have been widely used as surrogates for evaluating the health effects of inhaled airborne particulate matter. To provide a thorough understanding of particle transport and deposition mechanisms in the rat nasal airway, this article presents a computational fluid dynamics (CFD) study of particle exposure in a realistic rat nasal passage under a resting flow condition. Particles covering a diameter range from 1 nm to 4 µm were passively released in front of the rat's breathing zone, and the Lagrangian particle tracking approach was used to calculate in idual particle trajectories. Detailed particle deposition analysis shows the deposition of inertial particles >2 µm is high in the rat nasal vestibule and more than 70% of all inhaled inertial particles were trapped in this region. While for diffusive nanoparticles, the vestibule filtration effect is reduced, only less than 60% of inhaled nanoparticles were blocked by the anterior nasal structures. The particle exposure in the olfactory region only shows notable deposition for diffusive nanoparticles, which peaks at 9.4% for 5 nm particles. Despite the olfactory deposition remains at a low level, the ratio between the olfactory and the main passage is kept around 30-40% for 10-800 nm particles, which indicates a particle-size-independent distribution pattern in the main nasal passage and olfactory. This study provides a deep understanding of particles deposition features in a rat nasal passage, and the research findings can aid toxicologist in inter-species exposure-response extrapolation study.
Partitioning of dispersed nanoparticles in a realistic nasal passage for targeted drug delivery
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.IJPHARM.2018.03.046
Abstract: The complex nasal structure poses obstacles for efficient nasal drug administration beyond the nasal valve, especially when targeting the olfactory region. This study numerically detailed the naturally inhaled nanoparticle transport process from the initial releasing locations to the final deposited sites using a realistic human nasal passage. Dispersed nanoparticles at different coronal cross-sections were partitioned into multiple groups according to their final deposited locations. Results showed inhaled nanoparticles are more likely to move along the septum. Olfactory deposited particles entered the nose through the inner superior corner of the nostril the middle meatus deposited particles entered the nose through the top third of the nostril the inferior deposited particles entered via the bottom floor regions of the nostril. Therefore, targeted nasal inhalation therapies that intentionally release therapeutic particles from these recognized regions at the nostril plane can considerably improve the resultant topical disposition doses. However, it remains challenging to completely prevent undesired particle depositions as particles coming from the same location may produce multiple-sites depositions due to partition overlapping. Nevertheless, the fraction of undesired particle deposition is anticipated to be reduced at a great extent compared to unplanned releasing approaches.
In-silico decongested trial effects on the impaired breathing function of a bulldog suffering from severe brachycephalic obstructive airway syndrome
Publisher: Elsevier BV
Date: 2023
DOI: 10.1016/J.CMPB.2022.107243
Abstract: Brachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results however, the long-term post-surgery outcome is not well known. In silico analysis provides an objective measure to quantify the respiratory function in postoperative dogs which is critical for successful long-term outcomes. A virtual surgery to open the airway can explore the ability for improved breathing in an obstructed airway of a patient dog, thus supporting surgeons in pre-surgery planning using computational fluid dynamics. In this study five surgical interventions were generated with a gradual increment of decongested levels in a bulldog based on computed tomography images. The effects of the decongested airways on the breathing function of a patient bulldog, i.e., airflow characteristics, pressure drop, wall shear stress, and air-conditioning capacity, were quantified by benchmarking against a clinically healthy bulldog using computational fluid dynamics (CFD) method. Our findings demonstrated a promising decrease in excessive airstream velocity, pressure drop, and wall shear stress in virtual surgical scenarios, while constantly preserving adequate air-conditioning efficiency. A linear fit curve was proposed to correlate the reduction in the pressure drop and decongested level. The in silico analysis is a viable tool providing visual and quantitative insight into new unexplored surgical techniques.
Particle deposition in the paranasal sinuses following endoscopic sinus surgery
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.COMPBIOMED.2019.103573
Abstract: Optimizing intranasal distribution and retention of topical therapy is essential in the management of patients with chronic rhinosinusitis, including those that have had functional endoscopic sinus surgery (FESS). Computational fluid dynamics analysis has not previously been used to investigate sinus nasal spray delivery in the complete post-operative sinonasal geometries of patients who have undergone FESS. Models of sinonasal cavities were created from postoperative magnetic resonance imaging scans in four patients, three of whom underwent a comprehensive FESS, the other a modified endoscopic Lothrop procedure. Spray simulations were conducted at different flow rates (5 L/min, 10 L/min and 15 L/min) using sixteen particle sizes ranging from 4 μm to 70μm, spray velocity of 10 m/s and plume angle of 15°. Two different spray insertion angles were compared. Airflow distribution in the sinuses was closely related to the patient's nasal geometry and surgical intervention, in particular a unique crossflow between nasal chambers was present for the Lothrop patient. Sinus deposition was generally more effective with inhalational transport of low-inertia particles outside of the range produced by many standard nasal sprays or nebulizer. This was true except in the Lothrop patient, since previous surgery had been performed removing most of the septum where high-inertia particles would normally deposit. For sinuses receiving minimal airflow, particle penetration was diminished and successful deposition in the region became more restricted by device parameters. Further research is needed to validate these findings and explore other spray variables in a wider spectrum of patients to ascertain a multi-level approach to optimizing drug delivery in the sinuses.
Unsteady particle deposition in a human nasal cavity during inhalation
Publisher: SAGE Publications
Date: 12-2010
DOI: 10.1260/1757-482X.2.4.207
Abstract: The present study investigates the deposition efficiency during the unsteady inhalation cycle by using Computational Fluid Dynamics (CFD). The unsteady inhalation profile was applied at the outlet of nasopharynx, which had a maximum flow rate of 40.3L/min which corresponds to an equivalent steady inhalation tidal volume flow rate of 24.6L/min. Aerodynamic particle sizes of 5μm and 20μm were studied in order to reflect contrasting Stokes numbered particle behaviour. Two particle deposition efficiencies in the nasal cavity versus time are presented. In general, the deposition of 5μm particles was much less than 20μm particles. The first 0.2 second of the inhalation cycle was found to be significant to the particle transport, since the majority of particles were deposited during this period (i.e. its residence time). Comparisons were also made with its equivalent steady inhalation flow rate which found that the unsteady inhalation produced lower deposition efficiency for both particle sizes.
Numerical modelling of nanoparticle deposition in the nasal cavity and the tracheobronchial airway
Publisher: Informa UK Limited
Date: 07-2011
DOI: 10.1080/10255842.2010.493510
Abstract: Recent advances in nanotechnology have seen the manufacture of engineered nanoparticles for many commercial and medical applications such as targeted drug delivery and gene therapy. Transport of nanoparticles is mainly attributed to the Brownian force which increases as the nanoparticle decreases to 1 nm. This paper first verifies a Lagrangian Brownian model found in the commercial computational fluid dynamics software Fluent before applying the model to the nasal cavity and the tracheobronchial (TB) airway tree with a focus on drug delivery. The average radial dispersion of the nanoparticles was 9x greater for the user-defined function model over the Fluent in-built model. Deposition in the nasal cavity was high for very small nanoparticles. The particle diameter range in which the deposition drops from 80 to 18% is between 1 and 10 nm. From 10 to 150 nm, however, there is only a small change in the deposition curve from 18 to 15%. A similar deposition curve profile was found for the TB airway.
Evaluation and improvements of RANS turbulence models for linear diffuser flows
Publisher: Elsevier BV
Date: 2013
Detailed micro-particle deposition patterns in the human nasal cavity influenced by the breathing zone
Publisher: Elsevier BV
Date: 07-2015
Prediction of convective heat transfer coefficients for the upper respiratory tracts of rat, dog, monkey, and humans
Publisher: SAGE Publications
Date: 08-2016
Abstract: In vivo studies involving mammal surrogate models for toxicology studies have restrictions related to animal protection and ethics. Computer models, i.e., in silico models, have great potential to contribute towards essential understanding of heat and mass transfer phenomena in respiratory tracts in place of in vivo and in vitro studies. Here, we developed numerical upper airway models of a rat, a dog, a monkey, and two humans by using computed tomography data and then applied computational fluid dynamics analysis. Convective heat transfer coefficients were precisely analysed as a function of breathing airflow rate. Based on the computational fluid dynamics simulation results, the correlations between Nusselt ( Nu) number and the product of the Reynolds ( Re) and Prandtl ( Pr) numbers were summarized. The heat transfer efficiency (order of h c and correlation of Nu and RePr) in the upper airway of the dog seems to match those of the human models. On the other hand, the results for the rat and monkey showed clear differences compared with those of human models. The identified fundamental qualities of convective heat transfer phenomena in airways for rats, dogs, monkeys, and humans, have enabled discussions about quantitative differences of heat and mass transfer efficiency between different animals/species.
Nano-particle deposition in laminar annular pipe flows
Publisher: Elsevier BV
Date: 08-2020
A numerical study of spray particle deposition in a human nasal cavity
Publisher: Informa UK Limited
Date: 11-2006
Surface mapping for visualization of wall stresses during inhalation in a human nasal cavity
Publisher: Elsevier BV
Date: 2014
DOI: 10.1016/J.RESP.2013.09.004
Abstract: Airflow analysis can assist in better understanding the physiology however the human nasal cavity is an extremely complicated geometry that is difficult to visualize in 3D space, let alone in 2D space. In this paper, an anatomically accurate 3D surface of the nasal passages derived from CT data was unwrapped and transformed into a 2D space, into a UV-domain (where u and v are the coordinates) to allow a complete view of the entire wrapped surface. This visualization technique allows surface flow parameters to be analyzed with greater precision. A UV-unwrapping tool is developed and a strategy is presented to allow deeper analysis to be performed. This includes (i) the ability to present instant comparisons of geometry and flow variables between any number of different nasal cavity models through normalization of the 2D unwrapped surface (ii) visualization of an entire surface in one view and (iii) a planar surface that allows direct 1D and 2D analytical solutions of diffusion of inhaled vapors and particles through the nasal walls. This work lays a foundation for future investigations that correlates adverse and therapeutic health responses to local inhalation of gases and particles.
Comment on “CFD modelling of air and particle flows in different airway models by Y.H. Kim, Z.B. Tong, H.K. Chan, R.Y. Yang, Journal of Aerosol Science, 134 (2019) 14–28”
Publisher: Elsevier BV
Date: 09-2022
Deposition of inhaled wood dust in the nasal cavity
Publisher: Informa UK Limited
Date: 2007
DOI: 10.1080/08958370701665525
Abstract: Detailed deposition patterns of inhaled wood dust in an anatomically accurate nasal cavity were investigated using computational fluid dynamics (CFD) techniques. Three wood dusts, pine dust, heavy oak dust, and light oak dust, with a particle size distribution generated by machining (Chung et al., 2000), were simulated at an inhalation flow rate of 10 L/min. It was found that the major particle deposition sites were the nasal valve region and anterior section of the middle turbinate. Wood dust depositing in these regions is physiologically removed much more slowly than in other regions. This leads to the surrounding layer of soft tissues being damaged by the deposited particles during continuous exposure to wood dust. Additionally, it was found that pine dust had a higher deposition efficiency in the nasal cavity than the two oak dusts, due to the fact that it comprises a higher proportion of larger sized particles. Therefore, this indicates that dusts with a large amount of fine particles, such as those generated by sanding, may penetrate the nasal cavity and travel further into the lung.
Wet surface wall model for latent heat exchange during evaporation
Publisher: Wiley
Date: 21-02-2022
DOI: 10.1002/CNM.3581
Abstract: Air conditioning is a dual heat and mass transfer process, and the human nasal cavity achieves this through the mucosal wall surface, which is supplied with an energy source through the sub‐epithelial network of capillaries. Computational studies of air conditioning in the nasal cavity have included temperature and humidity, but most studies solved these flow parameters separately, and in some cases, a constant mucosal surface temperature was used. Recent developments demonstrated that both heat and mass transfer need to be modeled. This work expands on existing modeling efforts in accounting for the nasal cavity's dual heat and mass transfer process by introducing a new subwall model, given in the Supplementary Materials. The model was applied to a pipe geometry, and a human nasal cavity was recreated from CT‐scans, and six inhalation conditions were studied. The results showed that when the energy transfer from the latent heat of evaporation is included, there is a cooling effect on the mucosal surface temperature.
Comparison of Micron and Nano Particle Deposition Patterns in a Realistic Human Nasal Cavity
Publisher: Springer Berlin Heidelberg
Date: 2009
Comparative Study of the Effects of Acute Asthma in Relation to a Recovered Airway Tree on Airflow Patterns
Publisher: Springer Berlin Heidelberg
Date: 2009
Computational modelling of nasal respiratory flow
Publisher: Informa UK Limited
Date: 11-11-2020
Computational fluid dynamics study of human-induced wake and particle dispersion in indoor environment
Publisher: SAGE Publications
Date: 19-08-2016
Abstract: The impact of human-induced wake flow and particle re-dispersion from floors in an indoor environment was investigated by performing computational fluid dynamics simulations with dynamic mesh of a moving manikin model in a confined room. The manikin motion was achieved by a dynamic layering mesh method to update new grids with each time step. Particle transport from the floors and its re-dispersion was tracked by a Lagrangian approach. A series of numerical simulations of three walking speeds were performed to compare the flow disturbance induced by the walking motion. The significant airflow patterns included: an upward-directed flow in front of the body combined with a high velocity downward-directed flow at the rear of the body a stagnant region behind the gap between the legs and counter-rotating vortices in the wake region. The airflow momentum induced by the moving body disturbed PM 2.5 particles that were initially at rest on the floor to lift and become re-suspended due to its interaction with the trailing wake. The residual flow disturbances after the manikin stopped moving continued to induce the particle to spread and deposit over time. The spatial and temporal characteristics of the particle dispersion and concentration showed that higher walking speed was conducive to reducing human's exposure to contaminants in breathing region.
A fast and simple numerical model for a deeply buried underground tunnel in heating and cooling applications
Publisher: Elsevier BV
Date: 2014
Inhalation and deposition of spherical and pollen particles after middle turbinate resection in a human nasal cavity
Publisher: Elsevier BV
Date: 12-2021
DOI: 10.1016/J.RESP.2021.103769
Abstract: Middle turbinate resection significantly alters the anatomy and redistributes the inhaled air. The superior half of the main nasal cavity is opened up, increasing accessibility to the region. This is expected to increase inhalation dosimetry to the region during exposure to airborne particles. This study investigated the influence of middle turbinate resection on the deposition of inhaled pollutants that cover spherical and non-spherical particles (e.g. pollen). A computational model of the nasal cavity from CT scans, and its corresponding post-operative model with virtual surgery performed was created. Two constant flow rates of 5 L/min, and 15 L/min were simulated under a laminar flow field. Inhaled particles including pollen (non-spherical), and a spherical particle with reference density of 1000 kg/m
A Review on Process and Practices in Operation and Design Modification of Ejectors
Publisher: MDPI AG
Date: 11-11-2021
Abstract: This work reviews the current operational condition and activities on design modification for different applications of ejectors. Ejectors being a simple mechanical system capable of performing multiple fluid related functions (vacuum generation, pumping, mixing, condensing and heat exchanging), have been an essential part of several industrial processes. Two areas have been emphasized internal flow and application-based modifications in components of ejectors. The geometry and inlet flow conditions were found to be the prime influencing factor of its performance. The objective and application-based modifications were performed on the primary nozzle, secondary nozzle, mixing chamber, throat and diffuser. The resultant performance was found to be dependent on operational condition and fluid type. This emphasizes the requirement of application-based design selection of the technology. In addition, the flow dynamics of condensing, non-condensing, particle and slurry flow has been studied based on available literatures. The one-point final objective is to identify the usability of primary water jet ejectors for active vapor transport and condensation, to replace vacuum pump and condenser in compact domestic water desalination system.
N95 respirator mask breathing leads to excessive carbon dioxide inhalation and reduced heat transfer in a human nasal cavity
Publisher: AIP Publishing
Date: 08-2021
DOI: 10.1063/5.0061574
Abstract: Face masks and respirators are used to filter inhaled air, which may contain airborne droplets and high particulate matter (PM) concentrations. The respirators act as a barrier to the inhaled and exhaled air, which may change the nasal airflow characteristics and air-conditioning function of the nose. This study aims to investigate the nasal airflow dynamics during respiration with and without an N95 respirator driven by airflow through the nasal cavity to assess the effect of the respirator on breathing conditions during respiration. To achieve the objective of this study, transient computational fluid dynamics simulations have been utilized. The nasal geometry was reconstructed from high-resolution Computed Tomography scans of a healthy 25-year-old female subject. The species transport method was used to analyze the airflow, temperature, carbon dioxide (CO2), moisture content (H2O), and temperature distribution within the nasal cavity with and without an N95 respirator during eight consecutive respiration cycles with a tidal volume of 500 ml. The results demonstrated that a respirator caused excessive CO2 inhalation by approximately 7× greater per breath compared with normal breathing. Furthermore, heat and mass transfer in the nasal cavity was reduced, which influences the perception of nasal patency. It is suggested that wearers of high-efficiency masks that have minimal porosity and low air exchange for CO2 regulation should consider the amount of time they wear the mask.
Spray characteristics from nasal spray atomization
Publisher: Elsevier BV
Date: 09-2022
Correlation of Nasal Mucosal Temperature and Nasal Patency—A Computational Fluid Dynamics Study
Publisher: Wiley
Date: 03-08-2022
DOI: 10.1002/LARY.30327
Abstract: Recent evidence suggests that detection of nasal mucosal temperature, rather than direct airflow detection, is the primary determinant of subjective nasal patency. This study examines the role of nasal mucosal temperature in the perception of nasal patency using in vivo and computational fluid dynamics (CFD) measurements. Healthy adult participants completed Nasal Obstruction Symptom Evaluation (NOSE) and Visual Analogue Scale (VAS) questionnaires. A temperature probe measured nasal mucosal temperature at the vestibule, inferior turbinate, middle turbinate, and nasopharynx bilaterally. Participants underwent a CT scan, used to create a 3D nasal anatomy model to perform CFD analysis of nasal mucosal and inspired air temperature and heat flux along with mucosal surface area where heat flux W/m 2 (SAHF50). Eleven participants with a median age of 27 (IQR 24 48) were recruited. Probe‐measured temperature values correlated strongly with CFD‐derived values ( r = 0.87, p 0.05). Correlations were seen anteriorly in the vestibule and inferior turbinate regions between nasal mucosal temperature and unilateral VAS ( r = 0.42–0.46 p 0.05), between SAHF50 and unilateral VAS ( r = −0.31 to −0.36 p 0.05) and between nasal mucosal temperature and SAHF50 ( r = −0.37 to −0.41 p 0.05). Subjects with high patency (VAS ≤10) had increased heat flux anteriorly compared with lower patency subjects (VAS p 0.05). Lower nasal mucosal temperature and higher heat flux within the anterior nasal cavity correlates with a perception of improved unilateral nasal patency in healthy in iduals. 4 Laryngoscope , 133:1328–1335, 2023
Comparative numerical modeling of inhaled micron-sized particle deposition in human and rat nasal cavities
Publisher: Informa UK Limited
Date: 25-09-2015
DOI: 10.3109/08958378.2015.1088600
Abstract: Micron-sized particle deposition in anatomically realistic models of a rat and human nasal cavity was numerically investigated. A steady laminar inhalation flow rate was applied and particles were released from the outside air. Particles showing equivalent total particle deposition fractions were classified into low, medium and high inertial particle. Typical particle sizes are 2.5, 9 and 20 μm for the human model and 1, 2 and 3 μm for the rat model, respectively. Using a surface-mapping technique the 3D nasal cavity surface was "unwrapped" into a 2D domain and the particle deposition locations were plotted for complete visual coverage of the domain surface. The total surface area comparison showed that the surface area of the human nasal model was about ten times the size of the rat model. In contrast, the regional surface area percentage analysis revealed the olfactory region of the rat model was significantly larger than all other regions making up ∼55.6% of the total surface area, while that of the human nasal model only occupying 10.5%. Flow pattern comparisons showed rapid airflow acceleration was found at the nasopharynx region and the nostril region for the human and rat model, respectively. For the human model, the main passage is the major deposition region for micro-particles. While for the rat model, it is the vestibule. Through comparing the regional deposition flux between human and rat models, this study can contribute towards better extrapolation approach of inhalation exposure data between inter-subject species.
Development of a computational fluid dynamics model for mucociliary clearance in the nasal cavity
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.JBIOMECH.2019.01.015
Abstract: Intranasal drug delivery has attracted significant attention because of the opportunity to deliver systemic drugs directly to the blood stream. However, the mucociliary clearance poses a challenge in gaining high efficacy of intranasal drug delivery because cilia continuously carry the mucus blanket towards the laryngeal region. To better understand mucus flow behaviour on the human nasal cavity wall, we present computational model development, and evaluation of mucus motion on a realistic nasal cavity model reconstructed from CT-scans. The model development involved two approaches based on the actual nasal cavity geometry namely: (i) unwrapped-surface model in 2D domain and (ii) 3D-shell model. Conservation equations of fluid motion were applied to the domains, where a mucus production source term was used to initiate the mucus motion. The analysis included mucus flow patterns, virtual saccharin tests and quantitative velocity magnitude analysis, which demonstrated that the 3D-shell model results provided better agreement with experimental data. The unwrapped-surface model also suffered from mesh-deformations during the unwrapping stage and this led to higher mucus velocity compared to experimental data. Therefore, the 3D-shell model was recommended for future mucus flow simulations. As a first step towards mucus motion modelling this study provides important information that accurately simulates a mucus velocity field on a human nasal cavity wall, for assessment of toxicology and efficacy of intranasal drug delivery.
External and near-nozzle spray characteristics of a continuous spray atomized from a nasal spray device
Publisher: Informa UK Limited
Date: 02-2012
Inhalation and deposition of carbon and glass composite fibre in the respiratory airway
Publisher: Elsevier BV
Date: 11-2013
Prediction of nasal spray drug absorption influenced by mucociliary clearance
Publisher: Public Library of Science (PLoS)
Date: 28-01-2021
DOI: 10.1371/JOURNAL.PONE.0246007
Abstract: Evaluation of nasal spray drug absorption has been challenging because deposited particles are consistently transported away by mucociliary clearance during diffusing through the mucus layer. This study developed a novel approach combining Computational Fluid Dynamics (CFD) techniques with a 1-D mucus diffusion model to better predict nasal spray drug absorption. This integrated CFD-diffusion approach comprised a preliminary simulation of nasal airflow, spray particle injection, followed by analysis of mucociliary clearance and drug solute diffusion through the mucus layer. The spray particle deposition distribution was validated experimentally and numerically, and the mucus velocity field was validated by comparing with previous studies. Total and regional drug absorption for solute radius in the range of 1 − 110 nm were investigated. The total drug absorption contributed by the spray particle deposition was calculated. The absorption contribution from particles that deposited on the anterior region was found to increase significantly as the solute radius became larger (diffusion became slower). This was because the particles were consistently moved out of the anterior region, and the delayed absorption ensured more solute to be absorbed by the posterior regions covered with respiratory epithelium. Future improvements in the spray drug absorption model were discussed. The results of this study are aimed at working towards a CFD-based integrated model for evaluating nasal spray bioequivalence.
How reliable is the extrapolation? localized particle deposition patterns in human/rat nasal cavities
Publisher: American Society of Mechanical Engineers
Date: 13-11-2015
Abstract: To improve the understanding of dose-response extrapolation from rat to human, regional micro-particle deposition patterns are numerically investigated and compared between human and rat realistic nasal cavities using Computational Fluid Dynamics (CFD). Resting breathing conditions are chosen and airflow patterns are visualised by streamlines. To have better comparisons of deposition patterns, deposited particles are projected into pre- ided 2D domains based on anatomical features using surface-mapping technique. The results show significant differences between human and rat due to the different nasal geometries, especially at vestibule regions. In human case, large micro-particles deposit primarily in vestibule, septum and pharynx and small micro-particles relatively scattered in the whole cavity. On the contrary, in the rat case, large and small micro-particles are captured by the first and second bend of vestibule region.
Effect of ventilation design on removal of particles in woodturning workstations
Publisher: Elsevier BV
Date: 2009
A smoke visualisation technique for wake flow from a moving human manikin
Publisher: Springer Science and Business Media LLC
Date: 24-08-2016
Magnetic resonance imaging evaluation of the distribution of spray and irrigation devices within the sinonasal cavities.
Publisher: Wiley
Date: 09-2019
DOI: 10.1002/ALR.22376
Abstract: Optimizing intranasal distribution and retention of nasal sprays is essential in the management of patients with chronic rhinosinusitis (CRS), including those that have had functional endoscopic sinus surgery (FESS). Despite multiple existing distribution studies, there remains a need for a technique that allows regionalization of particle deposition within a patient's unique 3-dimensional (3D) geometry without exposing the patient to radiation. Seven participants delivered normal saline containing a gadolinium-based contrast agent (GBCA) by either saline irrigation or nasal sprays on 1 side of the nasal cavity. The saline irrigation group included 2 participants (both healthy) while the nasal spray group included 5 participants (2 healthy, 2 post-FESS patients, 1 CRS patient without any sinus surgery). The distribution of new signal enhancement was assessed on each participant using magnetic resonance imaging (MRI). Serial scans were performed over an interval of 4 minutes in the nasal spray group to assess changes in intranasal distribution over time. Signal enhancement was widespread within the nasal cavities and maxillary sinuses of participants (both healthy) that underwent sinus irrigation. For the nasal spray participants, the hotspots for signal enhancement were similar regardless of disease status or previous history of surgery. These included the internal nasal valve, anterior septum, inferior surface of the inferior turbinate, nasal floor, and nasopharynx. No signal enhancement was detected with nasal sprays in either unoperated or operated paranasal sinuses. A technique has been developed using MRI evaluation of radioopaque contrast to characterize the temporospatial distribution of topical drug delivery within the sinonasal cavities.
Image-based computational hemodynamics evaluation of atherosclerotic carotid bifurcation models
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.COMPBIOMED.2013.06.013
Abstract: Widely accepted treatment for carotid artery stenosis includes stenting as well as carotid endoarterectomy (CEA), despite complications associated with distal embolism. Therefore pre-screening for evaluating the extent of a stenosis is critically important before undertaking surgical procedures. This study presents and evaluates the feasibility of implementing a virtual computational hemodynamics platform for clinical use to determine the severity of a stenosis and give guidance for surgical decision making. The virtual platform incorporates high-resolution three-dimensional angiography results with Computational Fluid Dynamics modeling to determine clinically related indicators. This includes wall shear stress (WSS), the spatial and temporal hemodynamic changes of blood flow within patient-specific carotid bifurcations, pressure drop coefficient, and severity stratification. The turn-around time for each computational modeling stage was examined which showed that the total time cost is practical and the proposed hemodynamics evaluation platform is reasonably efficient for clinical diagnosis. Furthermore the virtual platform may be used to detect the hemodynamic consequence of atherogenesis, which can then be addressed and quantified based on the distribution of WSS related flow indicators on the abnormal luminal fractions. Additional functional evidence and data can be used by the overseeing physician to enrich and complement the anatomical information for more in-depth evaluation of stenosis in a reasonable time duration.
Performance Study of Eductor with Finite Secondary Source for Membrane Distillation
Publisher: MDPI AG
Date: 17-11-2022
DOI: 10.3390/EN15228620
Abstract: This is an experimental work performed to identify the influence of direct contact condensation inside an eductor. The fluid used in the experiments is water in two different phases: liquid and vapor, for primary and secondary flows, respectively. This study was conducted in an attempt to establish the suitability of an eductor as a combined vacuum generator and condenser for membrane desalination applications. The pressure and temperature measurements at critical points in the flow paths have been summarized to identify the influence of primary flow on secondary fluid saturation and condensation. In addition, the mechanism of phase change has been explained through the photography of fluid flow in a two-dimensional eductor. A consistent oscillation of the gas-liquid interface was observed during steady-state operations of the eductor. This work also contributes to the validation of future computational research. It will provide a baseline for computational thermal fluid analysis related to the mixing of condensing and non-condensing flow. In general, the research encompasses the practical operational scenario and provides information on the heat and mass transfer of direct contact condensation with a finite secondary source.
Ultrafine particle deposition in a realistic human airway at multiple inhalation scenarios
Publisher: Wiley
Date: 29-05-2019
DOI: 10.1002/CNM.3215
Local deposition fractions of ultrafine particles in a human nasal-sinus cavity CFD model
Publisher: Informa UK Limited
Date: 07-2012
DOI: 10.3109/08958378.2012.694494
Abstract: Ultrafine particle deposition studies in the human nasal cavity regions often omit the paranasal sinus regions. Because of the highly diffusive nature of nanoparticles, it is conjectured that deposition by diffusion may occur in the paranasal sinuses, which may affect the residual deposition fraction that leaves the nasal cavity. Two identical CFD models of a human nasal cavity, one with sinuses and one without, were reconstructed from CT-scans to determine the uptake of ultrafine particles. In general, there was little flow passing through the paranasal sinuses. However, flow patterns revealed that some streamlines reached the upper nasal cavity near the olfactory regions. These flow paths promote particle deposition in the sphenoid and ethmoid sinuses. It was found that there were some differences in the deposition fractions and patterns for 5 and 10 nm particles between the nasal-sinus and the nasal cavity models. This difference is lified when the flow rate is decreased and at a flow rate of 4 L/min the maximum difference was 17%. It is suggested that evaluations of nanoparticle deposition should consider some deposition occurring in the paranasal sinuses especially if flow rates are of concern.
Numerical and Experimental Analysis of Inhalation Airflow Dynamics in a Human Pharyngeal Airway
Publisher: MDPI AG
Date: 28-02-2020
Abstract: This paper presents a computational and experimental study of steady inhalation in a realistic human pharyngeal airway model. To investigate the intricate fluid dynamics inside the pharyngeal airway, the numerical predicted flow patterns are compared with in vitro measurements using Particle Image Velocimetry (PIV) approach. A structured mesh with 1.4 million cells is used with a laminar constant flow rate of 10 L/min. PIV measurements are taken in three sagittal planes which showed flow acceleration after the pharynx bend with high velocities in the posterior pharyngeal wall. Computed velocity profiles are compared with the measurements which showed generally good agreements with over-predicted velocity distributions on the anterior wall side. Secondary flow patterns on cross-sectional slices in the transverse plane revealed vortices posterior of pharynx and a pair of secondary flow vortexes due to the abrupt cross-sectional area increase. Finally, pressure and flow resistance analysis demonstrate that greatest pressure occurs in the superior half of the airway and maximum in-plane pressure variation is observed at the velo-oropharynx junction, which expects to induce a high tendency of airway collapse during inhalation. This study provides insights of the complex fluid dynamics in human pharyngeal airway and can contribute to a reliable approach to assess the probability of flow-induced airway collapse and improve the treatment of obstructive sleep apnea.
Machine learning and sensitivity analysis for predicting nasal drug delivery for targeted deposition
Publisher: Elsevier BV
Date: 07-2023
Particle inhalation and deposition in a human nasal cavity from the external surrounding environment
Publisher: Elsevier BV
Date: 2012
Fluid–structure interaction analysis of the left coronary artery with variable angulation
Publisher: Informa UK Limited
Date: 05-06-2015
DOI: 10.1080/10255842.2014.921682
Abstract: The aim of this study is to elucidate the correlation between coronary artery branch angulation, local mechanical and haemodynamic forces at the vicinity of bifurcation. Using a coupled fluid-structure interaction (FSI) modelling approach, five idealized left coronary artery models with various angles ranging from 70° to 110° were developed to investigate the influence of branch angulations. In addition, one CT image-based model was reconstructed to further demonstrate the medical application potential of the proposed FSI coupling method. The results show that the angulation strongly alters its mechanical stress distribution, and the instantaneous wall shear stress distributions are substantially moderated by the arterial wall compliance. As high tensile stress is hypothesized to cause stenosis, the left circumflex side bifurcation shoulder is indicated to induce atherosclerotic changes with a high tendency for wide-angled models.
Effect of morphology on nanoparticle transport and deposition in human upper tracheobronchial airways
Publisher: SAGE Publications
Date: 21-02-2018
Abstract: Aerosol transport and deposition in human lungs has attracted considerable attention in the past few years, as it has significant value to the study of toxicity consequence as well as therapeutic potential in occupational health and medical applications. In reproducing human tracheobronchial airways, two approaches were frequently taken: (1) anatomical realistic reconstruction through image scans (e.g. CT and MRI) or cadaver casts and (2) mathematical description using simplified models. Strengths and limitations are primarily focused on accuracy, resolution, repeatability, and computational\\physical expenses. While both approaches were reported in literature, detailed comparison of aerosol transport and deposition in the two representations were scarcely performed, largely due to the challenge to acquire comprehensive data from the irregular structured airway replicas (approach 1). To fill the gap, the current study performed a numerical comparison of nanoparticle transport and deposition in human upper tracheobronchial airways by using an anatomical realistic reconstruction (through CT scans) and a mathematically simplified airway model. As the first step, the current study was focused on the variation in breathing airflow pattern and the effect towards fate of the inhaled nanoparticles in human upper tracheobronchial airways. The study provided important information to understand geometric sensitivity of nanoparticle modeling in the human tracheobronchial tree and is of significant value to predict the whole lung uptake of inhaled nanoparticles in the human respiratory system.
Optimising nasal spray parameters for efficient drug delivery using computational fluid dynamics
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.COMPBIOMED.2008.03.008
Abstract: Experimental images from particle/droplet image analyser (PDIA) and particle image velocimetry (PIV) imaging techniques of particle formation from a nasal spray device were taken to determine critical parameters for the study and design of effective nasal drug delivery devices. The critical parameters found were particle size, diameter of spray cone at a break-up length and a spray cone angle. A range of values for each of the parameters were ascertained through imaging analysis which were then transposed into initial particle boundary conditions for particle flow simulation within the nasal cavity by using Computational Fluid Dynamics software. An Eulerian-Lagrangian scheme was utilised to track mono-dispersed particles (10 and 20 microm) at a breathing rate of 10 L/min. The results from this qualitative study aim to assist the pharmaceutical industry to improve and help guide the design of nasal spray devices.
Computational investigation of dust mite allergens in a realistic human nasal cavity.
Publisher: Informa UK Limited
Date: 12-05-2019
Simulation of a Fast-Charging Porous Thermal Energy Storage System Saturated with a Nano-Enhanced Phase Change Material
Publisher: MDPI AG
Date: 12-03-2021
DOI: 10.3390/EN14061575
Abstract: The melting of a coconut oil–CuO phase change material (PCM) embedded in an engineered nonuniform copper foam was theoretically analyzed to reduce the charging time of a thermal energy storage unit. A nonuniform metal foam could improve the effective thermal conductivity of a porous medium at regions with dominant conduction heat transfer by increasing local porosity. Moreover, the increase in porosity contributes to flow circulation in the natural convection-dominant regimes and adds a positive impact to the heat transfer rate, but it reduces the conduction heat transfer and overall heat transfer. The Taguchi optimization method was used to minimize the charging time of a shell-and-tube thermal energy storage (TES) unit by optimizing the porosity gradient, volume fractions of nanoparticles, average porosity, and porous pore sizes. The results showed that porosity is the most significant factor and lower porosity has a faster charging rate. A nonuniform porosity reduces the charging time of TES. The size of porous pores induces a negligible impact on the charging time. Lastly, the increase in volume fractions of nanoparticles reduces the charging time, but it has a minimal impact on the TES unit’s charging power.
CFD simulation of aerosol delivery to a human lung via surface acoustic wave nebulization
Publisher: Springer Science and Business Media LLC
Date: 22-07-2017
DOI: 10.1007/S10237-017-0936-0
Abstract: Administration of drug in the form of particles through inhalation is generally preferable in the treatment of respiratory disorders. Conventional inhalation therapy devices such as inhalers and nebulizers, nevertheless, suffer from low delivery efficiencies, wherein only a small fraction of the inhaled drug reaches the lower respiratory tract. This is primarily because these devices are not able to produce a sufficiently fine drug mist that has aerodynamic diameters on the order of a few microns. This study employs computational fluid dynamics to investigate the transport and deposition of the drug particles produced by a new aerosolization technique driven by surface acoustic waves (SAWs) into an in silico lung model geometrically reconstructed using computed tomography scanning. The particles generated by the SAW are released in different locations in a spacer chamber attached to a lung model extending from the mouth to the 6th generation of the lung bronchial tree. An Eulerian approach is used to solve the Navier-Stokes equations that govern the airflow within the respiratory tract, and a Lagrangian approach is adopted to track the particles, which are assumed to be spherical and inert. Due to the complexity of the lung geometry, the airflow patterns vary as it penetrates deeper into the lung. High inertia particles tend to deposit at locations where the geometry experiences a significant reduction in cross section. Our findings, nevertheless, show that the injection location can influence the delivery efficiency: Injection points close to the spacer centerline result in deeper penetration into the lung. Additionally, we found that the ratio of drug particles entering the right lung is significantly higher than the left lung, independent of the injection location. This is in good agreement with this fact that the most of airflow enters to the right lobes.
CFD modeling of spray atomization for a nasal spray device
Publisher: Informa UK Limited
Date: 11-2012
Design Enhancement of Eductor for Active Vapor Transport and Condensation during Two-Phase Single-Species Flow
Publisher: MDPI AG
Date: 25-01-2023
DOI: 10.3390/EN16031265
Abstract: This study is focused on enhancing secondary vapor entrainment and direct-contact condensation in a water jet eductor for the purpose of developing a compact, medium-scale desalination system. It encompasses an extended investigation of an eductor as a condenser, or heat exchanger, for the entrained phase. Exergy study, experimental measurement, and computational analysis are the primary methodologies employed in this work. The target parameters of the optimization work were set through exergetic analysis to identify the region of maximum exergy destruction. In the case of water and water vapor as primary and secondary fluids, mixing and condensation initiates in the mixing chamber of the eductor and is where the maximum exergy destruction was calculated. Therefore, multi-jet primary nozzle eductors were studied to determine the effect of increased interphase interaction area on the exergy destruction and the maximum suction and cooling capacities. Increases in the entrainment ratio, condensation rate and heat transfer coefficient were noted for increasing numbers of nozzles when comparing one-, two- and three-jet eductors.
Human nasal olfactory deposition of inhaled nanoparticles at low to moderate breathing rate
Publisher: Elsevier BV
Date: 11-2017
Microparticle Transport and Deposition in the Human Oral Airway: Toward the Smart Spacer
Publisher: Informa UK Limited
Date: 06-10-2015
New insights into the breathing physiology from transient respiratory nasal simulation
Publisher: AIP Publishing
Date: 11-2022
DOI: 10.1063/5.0112223
Abstract: The flow characteristics and heat transfer during nasal breathing in the complete human upper airway were investigated through the respiratory cycle using transient numerical simulations. We postulate that the complete airway from the nasal cavity to the trachea most accurately represents dynamic airflow patterns during inhalation and exhalation as they are likely to be affected by downstream anatomical structures. A 3D model was constructed from a healthy adult computed tomography scan. Computational fluid dynamics simulations were performed with Ansys Fluent software [ANSYS Fluent, R1 User's Guide (ANSYS, Inc., 2020)] using the stress-blended eddy simulation turbulence model looking at airflow patterns, velocity, mucosal temperature, and humidity (H2O fraction). One and a half breathing cycles were simulated for a total of 5.65 s, where the first inhalation cycle was discarded to avoid start-up effects. The results demonstrated that airway geometry structures, including the turbinates, the soft palate, and the glottic region, affect the flow patterns differently during inspiration and expiration. It also demonstrated phenomena not seen in steady flow simulations or in those without the lower respiratory tract geometry, including the nasopharyngeal temperature imprint during inhalation, the nasopharyngeal jet during exhalation, and the flow structures of the larynx and laryngeal jet. The inclusion of the exhalation phase demonstrates airflow preconditioning before inhalation, which we postulate contributes to achieving alveolar conditions. Alveolar temperature and humidity conditions are not achieved by the nasal cavity alone, and we demonstrate the contribution of the nasopharynx and larynx to air conditioning. Including the complete airway with realistic anatomy and using transient airflow modeling provided new insights into the physiology of the respiratory cycle.
Nano-particle deposition in axisymmetric annular pipes with thread
Publisher: Informa UK Limited
Date: 09-05-2019
A unifying correlation for laminar particle deposition in 90-degree pipe bends
Publisher: Elsevier BV
Date: 03-2019
Primary break-up and atomization characteristics of a nasal spray
Publisher: Public Library of Science (PLoS)
Date: 05-08-2020
Flow Patterns and Particle Residence Times in the Oral Cavity during Inhaled Drug Delivery
Publisher: MDPI AG
Date: 13-10-2022
DOI: 10.3390/PH15101259
Abstract: Pulmonary drug delivery aims to deliver particles deep into the lungs, bypassing the mouth–throat airway geometry. However, micron particles under high flow rates are susceptible to inertial impaction on anatomical sites that serve as a defense system to filter and prevent foreign particles from entering the lungs. The aim of this study was to understand particle aerodynamics and its possible deposition in the mouth–throat airway that inhibits pulmonary drug delivery. In this study, we present an analysis of the aerodynamics of inhaled particles inside a patient-specific mouth–throat model generated from MRI scans. Computational Fluid Dynamics with a Discrete Phase Model for tracking particles was used to characterize the airflow patterns for a constant inhalation flow rate of 30 L/min. Monodisperse particles with diameters of 7 μm to 26 μm were introduced to the domain within a 3 cm-diameter sphere in front of the oral cavity. The main outcomes of this study showed that the time taken for particle deposition to occur was 0.5 s a narrow stream of particles (medially and superiorly) were transported by the flow field larger particles 20 μm deposited onto the oropharnyx, while smaller particles 12 μm were more disperse throughout the oral cavity and navigated the curved geometry and laryngeal jet to escape through the tracheal outlet. It was concluded that at a flow rate of 30 L/min the particle diameters depositing on the larynx and trachea in this specific patient model are likely to be in the range of 7 μm to 16 μm. Particles larger than 16 μm primarily deposited on the oropharynx.
Pressure distribution and flow dynamics in a nasal airway using a scale resolving simulation
Publisher: AIP Publishing
Date: 2021
DOI: 10.1063/5.0036095
Abstract: Airflow through the nasal cavity exhibits a wide variety of fluid dynamic behaviors due to the intricacy of the nasal geometry. The flow is naturally unsteady and perhaps turbulent, despite Computational Fluid Dynamics (CFD) in the literature being assumed as having a steady laminar flow. Time-dependent simulations can be used to generate detailed data with the potential to uncover new flow behavior, although they are more computationally intensive than steady-state simulations. Furthermore, verification of CFD results has relied on a reported pressure drop (e.g., nasal resistance) across the nasal airway although the geometries used are different. This study investigated the unsteady nature of inhalation at flow rates of 10 l/min, 15 l/min, 20 l/min, and 30 l/min. A scale resolving CFD simulation using a hybrid Reynolds-averaged Navier–Stokes--large eddy simulation model was used and compared with experimental measurements of the pressure distribution and the overall pressure drop in the nasal cavity. The experimental results indicated a large pressure drop across the nasal valve and across the nasopharynx, with the latter attributed to a narrow cross-sectional area. At a flowrate of 30 l/min, the CFD simulations showed that the anterior half of the nasal cavity displayed dominantly laminar but disturbed flow behavior in the form of velocity fluctuations. The posterior half of the nasal cavity displayed turbulent activity, characterized by erratic fluctuating velocities, which was enhanced by the wider cross-sectional areas in the coronal plane. At 15 l/min, the flow field was laminar dominant with very little disturbance, confirming a steady-state laminar flow assumption is viable at this flow rate.
Numerical study of fibre deposition in a human nasal cavity
Publisher: Elsevier BV
Date: 03-2008
High resolution visualization and analysis of nasal spray drug delivery
Publisher: Springer Science and Business Media LLC
Date: 19-02-2014
DOI: 10.1007/S11095-013-1294-Y
Abstract: Effective nasal drug delivery of new-generation systemic drugs requires efficient devices that can achieve targeted drug delivery. It has been established that droplet size, spray plume, and droplet velocity are major contributors to drug deposition. Continual effort is needed to better understand and characterise the physical mechanisms underpinning droplet formation from nasal spray devices. High speed laser photography combined with an in-house designed automated actuation system, and a highly precise traversing unit, measurements and images magnified in small field-of-view regions within the spray was performed. The qualitative results showed a swirling liquid sheet at the near-nozzle region as the liquid is discharged before ligaments of fluid are separated off the liquid sheet. Droplets are formed and continue to deform as they travel downstream at velocities of up to 20 m/s. Increase in actuation pressure produces more rapid atomization and discharge time where finer droplets are produced. The results suggest that device designs should consider reducing droplet inertia to penetrate the nasal valve region, but find a way to deposit in the main nasal passage and not escape through to the lungs.
Time history of diesel particle deposition in cylindrical dielectric barrier discharge reactors
Publisher: Springer Science and Business Media LLC
Date: 12-2016
Simulation of sprayed particle deposition in a human nasal cavity including a nasal spray device
Publisher: Elsevier BV
Date: 02-2011
Geometry and airflow dynamics analysis in the nasal cavity during inhalation
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.CLINBIOMECH.2017.10.006
Abstract: A major issue among computational respiratory studies is the wide variety of nasal morphologies being studied, caused by both inter-population and inter-subject variations. Six nasal cavity geometries exhibiting erse geometry variations were subjected to steady inhalation flow rate of 15L/min. to determine if any consistent flow behaviour could be found. Despite vastly different geometries we were able to identify consistent flow patterns including relatively high velocity in the nasal valve region, followed by flow continuing predominantly in the inferior half of the airway. We also found conformity among models where the inhaled air reached a near-conditioned state by the middle of the nasal cavity. Air from the front of the face reached the olfactory regions while air from the lateral sides of the face moved through the inferior half of the nasal cavity. The ability to predict gross flow features provides a baseline flow field to compare against. This contributes towards establishing well defined flow predictions and be used as a comparison for future larger studies.
Numerical and Experimental Analysis of Drug Inhalation in Realistic Human Upper Airway Model
Publisher: MDPI AG
Date: 07-03-2023
DOI: 10.3390/PH16030406
Abstract: The demand for a more efficient and targeted method for intranasal drug delivery has led to sophisticated device design, delivery methods, and aerosol properties. Due to the complex nasal geometry and measurement limitations, numerical modeling is an appropriate approach to simulate the airflow, aerosol dispersion, and deposition for the initial assessment of novel methodologies for better drug delivery. In this study, a CT-based, 3D-printed model of a realistic nasal airway was reconstructed, and airflow pressure, velocity, turbulent kinetic energy (TKE), and aerosol deposition patterns were simultaneously investigated. Different inhalation flowrates (5, 10, 15, 30, and 45 L/min) and aerosol sizes (1, 1.5, 2.5, 3, 6, 15, and 30 µm) were simulated using laminar and SST viscous models, with the results compared and verified by experimental data. The results revealed that from the vestibule to the nasopharynx, the pressure drop was negligible for flow rates of 5, 10, and 15 L/min, while for flow rates of 30 and 40 L/min, a considerable pressure drop was observed by approximately 14 and 10%, respectively. However, from the nasopharynx and trachea, this reduction was approximately 70%. The aerosol deposition fraction alongside the nasal cavities and upper airway showed a significant difference in pattern, dependent on particle size. More than 90% of the initiated particles were deposited in the anterior region, while just under 20% of the injected ultrafine particles were deposited in this area. The turbulent and laminar models showed slightly different values for the deposition fraction and efficiency of drug delivery for ultrafine particles (about 5%) however, the deposition pattern for ultrafine particles was very different.
Numerical simulations for detailed airflow dynamics in a human nasal cavity
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.RESP.2008.01.012
Abstract: Nasal physiology is dependent on the physical structure of the nose. In idual aspects of the nasal cavity such as the geometry and flow rate collectively affect nasal function such as the filtration of foreign particles by bringing inspired air into contact with mucous-coated walls, humidifying and warming the air before it enters the lungs and the sense of smell. To better understand the physiology of the nose, this study makes use of CFD methods and post-processing techniques to present flow patterns between the left and right nasal cavities and compared the results with experimental and numerical data that are available in literature. The CFD simulation adopted a laminar steady flow for flow rates of 7.5 L/min and 15 L/min. General agreement of gross flow features were found that included high velocities in the constrictive nasal valve area region, high flow close to the septum walls, and vortex formations posterior to the nasal valve and olfactory regions. The differences in the left and right cavities were explored and the effects it had on the flow field were discussed especially in the nasal valve and middle turbinate regions. Geometrical differences were also compared with available models.
In silico approaches to respiratory nasal flows: A review
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.JBIOMECH.2019.109434
Abstract: The engineering discipline of in silico fluid dynamics delivers quantitative information on airflow behaviour in the nasal regions with unprecedented detail, often beyond the reach of traditional experiments. The ability to provide visualisation and analysis of flow properties such as velocity and pressure fields, as well as wall shear stress, dynamically during the respiratory cycle may give significant insight to clinicians. Yet, there remains ongoing challenges to advance the state-of-the-art further, including for ex le the lack of comprehensive CFD modelling on varied cohorts of patients. The present article embodies a review of previous and current in silico approaches to simulating nasal airflows. The review discusses specific modelling techniques required to accommodate physiologically- and clinically-relevant findings. It also provides a critical summary of the reported results in the literature followed by an outlook on the challenges and topics anticipated to drive research into the future.
Quantification of airflow in the sinuses following functional endoscopic sinus surgery
Publisher: Stichting Nase
Date: 04-2020
DOI: 10.4193/RHIN19.387
From the Cover: Comparative Numerical Modeling of Inhaled Nanoparticle Deposition in Human and Rat Nasal Cavities
Publisher: Oxford University Press (OUP)
Date: 13-05-2016
Abstract: To gain a better understanding of nanoparticle exposure in human nasal cavities, laboratory animals (e.g. rat) are used for in vivo studies. However, due to anatomical differences between human and rodent nasal cavities, direct particle deposition comparisons between species are difficult. This paper presents a comparative nanoparticle (1 nm, 10 nm, and 100 nm) deposition study using anatomically realistic models of a human and rat nasal cavity. The particle deposition fraction was highest consistently in the main nasal passage, for all nanoparticles tested, in the human model whereas this was only the case for 10 nm, and 100 nm particles for the rodent model, where greater deposition was found in the anterior nose for 1 nm particles. A deposition intensity (DI) term was introduced to represent the accumulated deposition fraction on cross-sectional slices. A common and preferential deposition site in the human model was found for all nanoparticles occurring at a distance of 3.5 cm inside the nasal passage. For the rodent model maximum DI occurred in the vestibule region at a distance of 0.3 cm, indicating that the rodent vestibule produces exceptionally high particle filtration capability. We also introduced a deposition flux which was a ratio of the regional deposition fraction relative to the region's surface area fraction. This value allowed direct comparison of deposition flux between species, and a regional extrapolation scaling factor was found (e.g. 1/10 scale for vestibule region for rat to human comparison). This study bridges the in vitro exposure experiments and in vivo nanomaterials toxicity studies, and can contribute towards improving inter-species exposure extrapolation studies in the future.
Comment on the European position paper on diagnostic tools in rhinology – computational fluid dynamics
Publisher: Stichting Nase
Date: 09-2019
DOI: 10.4193/RHIN19.269
Vortex structures and wake flow analysis from moving manikin models
Publisher: SAGE Publications
Date: 05-01-2020
Abstract: Vortex shedding in the wake flow generated by moving bodies exerts considerable influence on pollutant dispersion. This study investigated the effects of different body shapes using scaled models 1/5th of realistic size, including thin and wide shapes, standing and walking poses. The airflow from moving bodies was simulated using computational fluid dynamics (CFD) with dynamic meshing to account for the manikin movement. Experimental data from a smoke visualisation technique provided validation data for computational simulations which included flow separation angle over the head computed through image processing. Vortex structures were visualised using an Omega vortex identification method and compared with experimental visualisations. The main objective of this study is to verify the CFD simulations with smoke visualisation in terms of predicting motion-induced vortex structures, thus helping identify contaminant transport around different shaped bodies during walking and when coming to a stop. The results showed matching locations and patterns of vortex structures between the smoke visualisation and CFD simulations. After the manikin came to a stop, the flow induced by the larger body was characterised by a longer residence time for airborne contaminants in the breathing region while a reduced flow residence time for the thinner bodied manikin.
Effects of nasal drug delivery device and its orientation on sprayed particle deposition in a realistic human nasal cavity
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.COMPBIOMED.2016.08.002
Abstract: In this study, the effects of nasal drug delivery device and the spray nozzle orientation on sprayed droplets deposition in a realistic human nasal cavity were numerically studied. Prior to performing the numerical investigation, an in-house designed automated actuation system representing mean adults actuation force was developed to produce realistic spray plume. Then, the spray plume development was filmed by high speed photography system, and spray characteristics such as spray cone angle, break-up length, and average droplet velocity were obtained through off-line image analysis. Continuing studies utilizing those experimental data as boundary conditions were applied in the following numerical spray simulations using a commercially available nasal spray device, which was inserted into a realistic adult nasal passage with external facial features. Through varying the particle releasing direction, the deposition fractions of selected particle sizes on the main nasal passage for targeted drug delivery were compared. The results demonstrated that the middle spray direction showed superior spray efficiency compared with upper or lower directions, and the 10µm agents were the most suitable particle size as the majority of sprayed agents can be delivered to the targeted area, the main passage. This study elaborates a comprehensive approach to better understand nasal spray mechanism and evaluate its performance for existing nasal delivery practices. Results of this study can assist the pharmaceutical industry to improve the current design of nasal drug delivery device and ultimately benefit more patients through optimized medications delivery.
Effect of Pressurized Metered Dose Inhaler Spray Characteristics and Particle Size Distribution on Drug Delivery Efficiency
Publisher: Mary Ann Liebert Inc
Date: 10-2017
Abstract: A key issue in pulmonary drug delivery is improvement of the delivery device for effective and targeted treatment. Pressurized metered dose inhalers (pMDIs) are the most popular aerosol therapy device for treating lung diseases. This article studies the effect of spray characteristics: injection velocity, spray cone angle, particle size distribution (PSD), and its mass median aerodynamic diameter (MMAD) on drug delivery. An idealized oral airway geometry, extending from mouth to the main bronchus, was connected to a pMDI device. Inhalation flow rates of 15, 30, and 60 L/min were used and drug particle tracking was a one-way coupled Lagrangian model. The results showed that most particles deposited in the pharynx, where the airway has a reduced cross-sectional area. Particle deposition generally decreased with initial spray velocity and with increased spray cone angle for 30 and 60 L/min flow rates. However, for 15 L/min flow rate, the deposition increased slightly with an increase in the spray velocity and cone angle. The effect of spray cone angle was more significant than the initial spray velocity on particle deposition. When the MMAD of a PSD was reduced, the deposition efficiency also reduces, suggesting greater rates of particle entry into the lung. The deposition rate showed negligible change when the MMAD was more than 8 μm. Spray injection angle and velocity change the drug delivery efficacy however, the efficiency shows more sensitivity to the injection angle. The 30 L/min airflow rate delivers spray particles to the lung more efficiently than 15 and 60 L/min airflow rate, and reducing MMAD can help increase drug delivery to the lung.
Computational Modelling of Gas-Particle Flows with Different Particle Morphology in the Human Nasal Cavity
Publisher: SAGE Publications
Date: 2009
DOI: 10.1260/175748209787387061
Abstract: This paper summarises current studies related to numerical gas-particle flows in the human nasal cavity. Of interest are the numerical modelling requirements to consider the effects of particle morphology for a variety of particle shapes and sizes such as very small particles sizes (nanoparticles), elongated shapes (asbestos fibres), rough shapes (pollen), and porous light density particles (drug particles) are considered. It was shown that important physical phenomena needed to be addressed for different particle characteristics. This included the Brownian diffusion for submicron particles. Computational results for the nasal capture efficiency for nano-particles and various breathing rates in the laminar regime were found to correlate well with the ratio of particle diffusivity to the breathing rate. For micron particles, particle inertia is the most significant property and the need to use sufficient drag laws is important. Drag correlations for fibrous and rough surfaced particles were investigated to enable particle tracking. Based on the simulated results, semi-empirical correlations for particle deposition were fitted in terms of Peclet number and inertial parameter for nanoparticles and micron particles respectively.
Inhalability of micron particles through the nose and mouth
Publisher: Informa UK Limited
Date: 13-01-2010
DOI: 10.3109/08958370903295204
Abstract: Aspiration efficiencies from nose and mouth inhalations are investigated at low and high inhalation rates by using the commercial Computational Fluid Dynamics (CFD) software CFX 11. A realistic human head with detailed facial features was constructed. Facial features were matched to represent the 50th percentile of a human male, aged between 20 and 65 years old, based on anthropometric data. The constant freestream velocity was 0.2 ms(-1), normal to the face, and inhalation rates through the mouth and nose were 15 liters per minute (LPM) for light breathing and 40 LPM for heavy breathing. It was found that the flow field in the near breathing region exhibited vertical direction caused by the presence of the torso where the airstream erges as it flows around and over the body. The critical area concept was used as a tool to determine the aspiration efficiency of particles. Comparisons between critical areas for the nose and mouth inhalations show similar geometric properties such as the area's shape, and its vertical distance location on the x-z plane located at y = 80 cm upstream. The critical area sizes were found to be slightly larger for the mouth inhalation mainly due to the larger mouth area and also the aligned orientation of the mouth to the upstream flow, whereas the nose is perpendicular to the upstream flow. This study was undertaken to establish the flow field in the near breathing region that will help to characterize the flow and particle field for initial boundary conditions leading to a more holistic modeling approach of respiration through the internal nasal cavity and mouth.
Antennal scales improve signal detection efficiency in moths
Publisher: The Royal Society
Date: 14-03-2018
Abstract: The elaborate bipectinate antennae of male moths are thought to increase their sensitivity to female sex pheromones, and so should be favoured by selection. Yet simple filamentous antennae are the most common structure among moths. The stereotypic arrangements of scales on the surface of antennae may resolve this paradox. We use computational fluid dynamics techniques to model how scales on the filamentous antennae of moths affect the passage of different particles in the airflow across the flagellum in both small and large moths. We found that the scales provide an effective solution to improve the efficacy of filamentous antennae, by increasing the concentration of nanoparticles, which resemble pheromones, around the antennae. The smaller moths have a greater increase in antennal efficiency than larger moths. The scales also ert microparticles, which resemble dust, away from the antennal surface, thereby reducing contamination. The positive correlations between antennal scale angles and sensilla number across Heliozelidae moths are consistent with the predictions of our model.
Performance Analysis of an Eductor-Based Membrane Distillation Unit
Publisher: MDPI AG
Date: 10-11-2022
DOI: 10.3390/W14223624
Abstract: Thermal desalination technologies involve two primary processes: vapor generation from saline water, and effective recovery of the resulting condensate. Membrane distillation (MD) systems are among the emerging thermal desalination technologies which use a hydrophobic membrane to recover condensate through either direct or indirect contact (with the cooling fluid) condensation. The specific process technology (for thermal energy transfer and condensate recovery) depends on the type of MD. Direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) are two significant MD processes, with DCMD having the advantage of direct condensation and simple design, while VMD systems have high yield through sub-atmospheric vapor generation. This work focuses on developing an eductor-based MD process incorporating the strengths of both DCMD and VMD. It is an experimental study with a water jet eductor replacing the vacuum pump and condenser in a typical VMD system for active permeate vapor transfer and condensation. Unlike the exiting VMD systems, the proposed design recovers condensate by direct contact condensation. The sub-cooled water acts as a motive flow which entrains the secondary vapor into the stream, causing mass transfer via condensation at the interface. The modified VMD was found to have achieved better flux compared to the conventional VMD system. The performance of the eductor, sensitivity to parameters, and the practicality of the technology have been analyzed.
Detailed predictions of particle aspiration affected by respiratory inhalation and airflow
Publisher: Elsevier BV
Date: 12-2012
Experimental and numerical investigation on a new type of heat exchanger in ground source heat pump system
Publisher: Springer Science and Business Media LLC
Date: 24-01-2015
Numerical investigation into the effects of wall roughness on a gas-particle flow in a 90° bend
Publisher: Elsevier BV
Date: 03-2008
Detailed computational analysis of flow dynamics in an extended respiratory airway model
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.CLINBIOMECH.2018.12.006
Abstract: Understanding respiratory physiology can aid clinicians in diagnosing the cause of respiratory symptoms or shed light on drug delivery inhaler device optimisation. However, the sheer complexity of the human lung prohibits a full-scale study. In this study, a realistic respiratory airway model including large-to-small conducting airways was built. This airway model consists of subject-specific upper and lower airways, extending from nasal and oral openings to terminal bronchioles (up to the 15th generation). Based on the subject-specific airway model, topological information was extracted and a digital reference model that exhibits strong asymmetry and multi-fractal properties was provided. Inhalation flow rates 18 L/min and 50 L/min were adopted to understand inspiratory conditions subjecting to resting and light exercise inhalation modes. Regional airflow in terms of axial velocity and secondary flow vortices along the lung airway model was extracted. Obvious secondary flow currents were seen in the larynx-trachea segment and left main bronchus, while for the terminal conducting airway in the right lower lobe, the airflow tends to be much smoother with no secondary flow currents. This paper provides insights on respiratory physiology, especially in the lower lung airways, and will be potentially useful for diagnosis of lower airway diseases.
The Impact of Adhesions on Nasal Airflow: A Quantitative Analysis Using Computational Fluid Dynamics.
Publisher: SAGE Publications
Date: 13-11-2022
DOI: 10.1177/19458924221137982
Abstract: Nasal adhesions (NAs) are a known complication of nasal airway surgery. Even minor NAs can lead to significant postoperative nasal airway obstruction (NAO). Division of such NAs often provides much greater relief than anticipated. We examine the impact of NAs at various anatomical sites on nasal airflow and mucosal cooling using computational fluid dynamics (CFD) and multiple test subjects. CT scans of healthy adult subjects were used to construct three-dimensional nasal airway computational models. A single virtual 2.5 mm diameter NA was placed at one of five sites commonly seen following NAO surgery within each nasal cavity bilaterally, resulting in 10 NA models and 1 NA-free control for each subject. CFD analysis was performed on each NA model and compared with the subject's NA-free control model. 4 subjects were recruited to create 44 computational models. The NAs caused the airflow streamlines to separate, leading to a statistically significant increase in mucosal temperature immediately downstream to the NAs (wake region). Changes in the mucosal temperature in the wake region of the NAs were most prominent in anteriorly located NAs with a mean increase of 1.62 °C for the anterior inferior turbinate NAs ( NAs result in marked disruption to airflow patterns and reduced mucosal cooling on critical surfaces, particularly in the wake region. Reduced wake region mucosal cooling may be a contributing factor to the exaggerated perception of nasal obstruction experienced by patients with NAs.
Combining experimental and computational techniques to understand and improve dry powder inhalers
Publisher: Informa UK Limited
Date: 02-01-2022
DOI: 10.1080/17425247.2022.2026922
Abstract: Dry Powder Inhalers (DPIs) continue to be developed to deliver an expanding range of drugs to treat an ever-increasing range of medical conditions with each drug and device combination needing a specifically designed inhaler. Fast regulatory approval is essential to be first to market, ensuring commercial profitability. Experimental techniques and computational methods are improving rapidly, but each needs a skilled user to maximize results obtained from these techniques. Multidisciplinary teams are therefore key to making optimal use of these methods and such qualified teams can provide enormous benefits to pharmaceutical companies to improve device efficacy and thus time to market. There is already a move to integrate the benefits of Industry 4.0 into inhaler design and usage, a trend that will accelerate.
In-vivo Experimental and Numerical Studies of Cardiac Flow in Right Atrium
Publisher: The Hong Kong Institution of Engineers
Date: 2010
Large eddy simulation of cough jet dynamics, droplet transport, and inhalability over a ten minute exposure
Publisher: AIP Publishing
Date: 12-2021
DOI: 10.1063/5.0072148
Abstract: High fidelity simulations of expiratory events such as coughing provide the opportunity to predict the fate of the droplets from the turbulent jet cloud produced from a cough. It is well established that droplets carrying infectious pathogens with diameters of 1–5 μm remain suspended in the air for several hours and transported by the air currents over considerable distances (e.g., in meters). This study used a highly resolved mesh to capture the multiphase turbulent buoyant cloud with suspended droplets produced by a cough. The cough droplets' dispersion was subjected to thermal gradients and evaporation and allowed to disperse between two humans standing 2 m apart. A nasal cavity anatomy was included inside the second human to determine the inhaled droplets. Three diameter ranges characterized the droplet cloud, & μm, which made up 93% of all droplets by number 5 to 100 μm comprised 3%, and & μm comprising 4%. The results demonstrated the temporal evolution of the cough event, where a jet is first formed, followed by a thermally driven puff cloud with the latter primarily composed of droplets under 5 μm diameter, moving with a vortex string structure. After the initial cough, the data were interpolated onto a more coarse mesh to allow the simulation to cover ten minutes, equivalent to 150 breathing cycles. We observe that the critical diameter size susceptible to inhalation was 0.5 μm, although most inhaled droplets after 10 min by the second human were approximately 0.8 μm. These observations offer insight into the risk of airborne transmission and numerical metrics for modeling and risk assessment.
Dynamic meshing modelling for particle resuspension caused by swinging manikin motion
Publisher: Elsevier BV
Date: 10-2017
Simulation of pharyngeal airway interaction with air flow using low-re turbulence model
Publisher: Hindawi Limited
Date: 2011
DOI: 10.1155/2011/510472
Abstract: This paper aims to simulate the interaction between a simplified tongue replica with expiratory air flow considering the flow in the pharyngeal airway to be turbulent. A three-dimensional model with a low-Re SST turbulence model is adopted. An Arbitrary Eulerian-Lagrangian description for the fluid governing equation is coupled with the Lagrangian structural solver via a partitioned approach, allowing deformation of the fluid domain to be captured. Both the three-dimensional flow features and collapsibility of the tongue are presented. In addition, examining initial constriction height ranging from 0.8 mm to 11.0 mm and tongue replica modulus from 1.25 MPa to 2.25 MPa, the influence of both of these parameters on the flow rate and collapsibility of the tongue is also investigated and discussed. Numerical simulations confirm expected predisposition of apneic patients with narrower airway opening to flow obstruction and suggest much severe tongue collapsibility if the pharyngeal flow regime is turbulent compared to laminar.
Nasal Irrigation Delivery in Three Post-FESS Models From a Squeeze-bottle Using CFD
Publisher: Springer Science and Business Media LLC
Date: 02-09-2022
DOI: 10.1007/S11095-022-03375-Y
Abstract: Nasal saline irrigation is highly recommended in patients following functional endoscopic sinus surgery (FESS) to aid the postoperative recovery. Post-FESS patients have significantly altered anatomy leading to markedly different flow dynamics from those found in pre-op or non-diseased airways, resulting in unknown flow dynamics. This work investigated how the liquid stream disperses through altered nasal cavities following surgery using Computational Fluid Dynamics (CFD). A realistic squeeze profile was determined from physical experiments with a 27-year-old male using a squeeze bottle with load sensors. The administration technique involved a head tilt of 45-degrees forward to represent a head position over a sink. After the irrigation event that lasted 4.5 s, the simulation continued for an additional 1.5 s, with the head orientation returning to an upright position. The results demonstrated that a large maxillary sinus ostium on the right side allows saline penetration into this sinus. The increased volume of saline entering the maxillary sinus limits the saline volume available to the rest of the sinonasal cavity and reduces the surface coverage of the other paranasal sinuses. The average wall shear stress was higher on the right side than on the other side for two patients. The results also revealed that head position alters the sinuses’ saline residual, especially the frontal sinuses. While greater access to sinuses is achieved through FESS surgery, patients without a nasal septum limits posterior sinus penetration due to the liquid crossing over to the contralateral cavity and exiting the nasal cavity early.
Computational assessment of the nasal air conditioning and paranasal sinus ventilation from nasal assisted breathing therapy
Publisher: AIP Publishing
Date: 05-2022
DOI: 10.1063/5.0090058
Abstract: Nasal cannula oxygen therapy is a common treatment option for patients with respiratory failure but needs further investigation to understand its potential for use for assisted breathing. Air with a high oxygen level is introduced into the nasal cavity using a nasal cannula during assisted breathing via oxygen therapy. The treatment impacts the nasal airflow dynamics and air-conditioning function. This study aims to investigate the nasal heat and mass transfer and sinus ventilation during assisted breathing at different operating conditions using computational fluid dynamics simulations. The nasal geometry was reconstructed from high-resolution computed tomography scans of a healthy subject. A constant inhalation flow rate of 15 LPM (liters per minute) was used, and the nasal cannula flow rate was set to between 5 and 15 LPM. The results demonstrated that assisted breathing at a high flow rate impacted sinus ventilation. It also changed the mucosal surface heat and mass transfer, thus inhaled air temperature and humidity. The high flow assisted breathing at 36 °C affected the nasal heat flux the most compared with other breathing conditions, while the low flow assisted breathing had minimal effect and, therefore, could be considered ineffective for any relevant treatment.
How Nanoparticle Aerosols Transport through Multi-Stenosis Sections of Upper Airways: A CFD-DPM Modelling
Publisher: MDPI AG
Date: 28-07-2022
Abstract: Airway stenosis is a global respiratory health problem that is caused by airway injury, endotracheal intubation, malignant tumor, lung aging, or autoimmune diseases. A precise understanding of the airflow dynamics and pharmaceutical aerosol transport through the multi-stenosis airways is vital for targeted drug delivery, and is missing from the literature. The object of this study primarily relates to behaviors and nanoparticle transport through the multi-stenosis sections of the trachea and upper airways. The combination of a CT-based mouth–throat model and Weibel’s model was adopted in the ANSYS FLUENT solver for the numerical simulation of the Euler–Lagrange (E-L) method. Comprehensive grid refinement and validation were performed. The results from this study indicated that, for all flow rates, a higher velocity was usually found in the stenosis section. The maximum velocity was found in the stenosis section having a 75% reduction, followed by the stenosis section having a 50% reduction. Increasing flow rate resulted in higher wall shear stress, especially in stenosis sections. The highest pressure was found in the mouth–throat section for all flow rates. The lowest pressure was usually found in stenosis sections, especially in the third generation. Particle escape rate was dependent on flow rate and inversely dependent on particle size. The overall deposition efficiency was observed to be significantly higher in the mouth–throat and stenosis sections compared to other areas. However, this was proven to be only the case for a particle size of 1 nm. Moreover, smaller nanoparticles were usually trapped in the mouth–throat section, whereas larger nanoparticle sizes escaped through the lower airways from the left side of the lung this accounted for approximately 50% of the total injected particles, and 36% escaped from the right side. The findings of this study can improve the comprehensive understanding of airflow patterns and nanoparticle deposition. This would be beneficial in work with polydisperse particle deposition for treatment of comprehensive stenosis with specific drugs under various disease conditions.
Computational Hemodynamics – Theory, Modelling and Applications
Publisher: Springer Netherlands
Date: 2015
Effects of airway obstruction induced by asthma attack on particle deposition
Publisher: Elsevier BV
Date: 06-2010
Computational fluid dynamics analysis of wall shear stresses between human and rat nasal cavities
Publisher: Elsevier BV
Date: 2017
Three-dimensional fluid-structure interaction modeling of expiratory flow in the pharyngeal airway
Publisher: Springer Berlin Heidelberg
Date: 2011
Editorial
Publisher: Informa UK Limited
Date: 02-04-2020
Study of the critical velocity of the tunnels using an analytical approach
Publisher: Elsevier BV
Date: 07-2021
Indoor particle inhalability of a stationary and moving manikin
Publisher: Elsevier BV
Date: 02-2020
The impact of nasal adhesions on airflow and mucosal cooling – A computational fluid dynamics analysis
Publisher: Elsevier BV
Date: 11-2021
DOI: 10.1016/J.RESP.2021.103719
Abstract: Nasal adhesions are a known postoperative complication following surgical procedures for nasal airway obstruction (NAO) and are a common cause of surgical failure, with patients often reporting significant NAO, despite relatively minor adhesion size. Division of such nasal adhesions often provides much greater relief than anticipated, based on the minimal reduction in cross-sectional area associated with the adhesion. The available literature regarding nasal adhesions provides little evidence examining their quantitative and qualitative effects on nasal airflow using objective measures. This study examined the impact of nasal adhesions at various anatomical sites on nasal airflow and mucosal cooling using computational fluid dynamics (CFD). A high-resolution CT scan of the paranasal sinuses of a 25-year-old, healthy female patient was segmented to create a three-dimensional nasal airway model. Virtual nasal adhesions of 2.5 mm diameter were added to various locations within the nasal cavity, representing common sites seen following NAO surgery. A series of models with single adhesions were created. CFD analysis was performed on each model and compared with a baseline no-adhesion model, comparing airflow and heat and mass transfer. The nasal adhesions resulted in no significant change in bulk airflow patterns through the nasal cavity. However, significant changes were observed in local airflow and mucosal cooling around and immediately downstream to the nasal adhesions. These were most evident with anterior nasal adhesions at the internal valve and anterior inferior turbinate. Postoperative nasal adhesions create local airflow disruption, resulting in reduced local mucosal cooling on critical surfaces, explaining the exaggerated perception of nasal obstruction. In particular, anteriorly located adhesions created greater disruption to local airflow and mucosal cooling, explaining their associated greater subjective sensation of obstruction.
Particle and inhalation exposure in human and monkey computational airway models.
Publisher: Informa UK Limited
Date: 15-10-2018
DOI: 10.1080/08958378.2018.1545810
Abstract: Regional deposition of inhaled aerosols is essential for assessing health risks from toxic exposure. Upper airway physiology plays a significant role in respiratory defense by filtering micrometer particles, whose deposition mechanism is predominantly inertial impaction and is mainly controlled by airflow characteristics. The monkey is commonly used in tests that study inhalation toxicity as well as in preclinical tests as human surrogates due to their anatomical similarities to humans. Therefore, accurate predictions and an understanding of the inhaled particles and their distribution in monkeys are essential for extrapolating laboratory animal data to humans. The study goals were as follows: (1) to predict the particle deposition based on aerodynamic diameters (1-10 µm) and various steady inspiratory flow rates in computational models of monkey and human upper airways and (2) to investigate potential differences in inhalation flow and particle deposition between humans and monkeys by comparing numerical simulation results with similar in-vitro and in-vivo measurements from recent literature. The deposition fractions of the monkey's numerical airway model agreed well with in-vitro and human model data when equivalent Stokes numbers were compared, based on the minimum cross-sectional area as representative of length scale. Vestibule removal efficiencies were predicted to be higher in the monkey model compared with the human model. Our results revealed that the particle transportations were sensitive to the anatomical structure, airway geometry, airflow rates, inflow boundary conditions and particle size.
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