ORCID Profile
0000-0003-3932-0370
Current Organisation
University of Sydney
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Turbulent Flows | Pharmaceutical Sciences | Powder and Particle Technology | Pharmacology and Pharmaceutical Sciences | Interdisciplinary Engineering | Chemical Engineering
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in the Chemical Sciences |
Publisher: American Chemical Society (ACS)
Date: 04-04-2022
Publisher: Elsevier BV
Date: 08-2022
Publisher: Elsevier BV
Date: 05-2019
Publisher: Informa UK Limited
Date: 12-12-2019
Publisher: Springer Science and Business Media LLC
Date: 26-02-2014
Publisher: IOP Publishing
Date: 24-12-2015
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.MEDENGPHY.2021.103746
Abstract: This study aims to utilise particle image velocimetry (PIV) techniques to investigate the time-dependant effects of respiratory rate in the extrathoracic airway, to show how they affect the flow field developed. There has been limited validation of computational fluid dynamics (CFD) models using experimental setups. Furthermore, the large majority of existing CFD models focus on rigid airways, not accounting for active deformation through the breathing cycle. Experiments were carried out to expand upon Zhao et al.'s previous study, in which a single respiratory rate was investigated. This studied utilised a transient, sinusoidal flow profile with two respiratory rates of 10 breaths per minute (BPM) and 25 BPM, both achieving a maximum flow rate correlating to 5 L/min in air to simulate tidal breathing. Results from this study showed that respiratory rate had the greatest influence near the onset of the inspiratory and expiratory manoeuvres, with the higher respiratory rate homogenising later in the cycle. It was shown that airway deformation at the level of the soft palate homogenised flow downstream of the deformation which resulted in a lower peak magnitude velocity for approximately 40% of the cycle at the level of the epiglottis, when compared to the rigid airway model.
Publisher: Elsevier BV
Date: 03-2021
Publisher: American Chemical Society (ACS)
Date: 31-12-2020
Publisher: Springer Science and Business Media LLC
Date: 05-12-2023
Publisher: Elsevier BV
Date: 2021
Publisher: American Society of Civil Engineers (ASCE)
Date: 10-2017
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 06-2011
Publisher: Elsevier BV
Date: 04-2015
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Informa UK Limited
Date: 19-01-2021
Publisher: Informa UK Limited
Date: 11-07-2022
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.IJPHARM.2022.121556
Abstract: In order to better understand powder dispersion in dry powder inhaler (DPI) devices, a new powder disperser was designed, which uses flow modifiers to alter powder fluidization behavior so as to physically replicate various flow conditions observed in a range of commercial DPIs. The influence of these modifiers on the performance of the DPI was analyzed for flowrates progressing from laminar (15 L/min) to transitional (30 L/min), and finally turbulent flow regimes (60 L/min) in the device. The aerosol performance of the disperser was measured using a Next Generation Impactor. For flowrate in the laminar regime, powder evacuation from the disperser was generally insufficient ( 85% when the device was operated in the turbulent flow regime. In contrast, the highest fine particle fraction (FPF) and lowest throat deposition were achieved when operating in the transitional flow regime. The FPF could be increased further by applying flow modifications such as narrowing the air passage before the powder pocket, inducing localized turbulence (by a grid) near the powder pocket, and by changing the loading position of the powder. Flow modifiers had the most noticeable effect under a laminar flow regime, however, the device operated most efficiently under a transitional flow regime.
Publisher: Elsevier BV
Date: 09-2021
Publisher: IOP Publishing
Date: 17-01-2017
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 12-2022
Publisher: Springer Science and Business Media LLC
Date: 16-09-2020
Publisher: Informa UK Limited
Date: 22-11-2017
DOI: 10.1080/17425247.2018.1406917
Abstract: The effectiveness of drug delivery to the lungs is inextricably linked to the fundamental interactions that occur between particles and flow in the extrathoracic airway. Research in this field requires time resolved in-vivo and in-vitro measurements of three separate, yet intricately linked parameters: i) airway flow, ii) airway geometry, and iii) drug particle characteristics. A number of recent significant developments have been made in the experimental diagnostic tools used to characterise these parameters. In this review paper, we summarize the key recent findings that have resulted from the implementation of laser and optical diagnostic tools towards characterization of airway flow, extrathoracic airway geometry and drug particle characteristics. These three areas are discussed together, enabling a critical review of the implications of recent experimental findings on likely future developments in drug delivery to the lungs. Improvements in drug delivery systems will result through implementation of laser and optical based diagnostic methods that can spatially and temporally resolve particle and agglomerate shape, size and dynamic characteristics. Design of inhaler devices must be done in parallel to developing realistic in-vitro upper airway replicas that account for physiological differences between patient groups, as a function of respiratory disease severity.
Publisher: Elsevier BV
Date: 03-2023
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 04-2021
Publisher: Cambridge University Press (CUP)
Date: 23-12-2014
DOI: 10.1017/JFM.2014.700
Abstract: Air-assisted primary atomization is investigated in a configuration where liquid is injected in a turbulent gaseous jet flow both within as well as outside of the potential core. Cases are studied where the injection point is moved within the flow to maintain a range of constant gaseous mean velocities but changing local fluctuating velocity root-mean-square (r.m.s.) levels. Over a range of mean conditions, this allows for a systematic understanding of both the effects of gas-phase turbulence and mean shear on primary break-up independently. Extensive data is obtained and analysed from laser Doppler anemometry hase Doppler anemometry, high-speed microscopic backlit imaging and advanced image processing. It is found that the ratio of the turbulent Weber number $\\mathit{We}^{\\prime }$ to the mean Weber number $\\mathit{We}$ is a relevant parameter as is the turbulence intensity. The primary break-up length is found to be heavily influenced not only by the mean velocity, but also by the turbulence level and the mass fuel to air ratio. Above a particular threshold intensity level the break-up time changes in proportion to the change in the integral time scale of the flow. In addition, it is found that regardless of diameter and turbulent flow conditions at the liquid jet, the final size of ligaments converges to a value which is of the order of the measured primary instability wavelength ( ${\\it\\lambda}_{1}$ ). In contrast, cases of different turbulence intensity show the mean of droplet sizes erging as the spray is advected downstream and this is because droplets are generated from ligaments, the latter of which are subjected both to Rayleigh–Taylor instabilities and turbulent fluctuations. This contribution, for the first time, examines the theoretical applicability of the Rayleigh–Taylor instability in flows where the turbulence is substantial with respect to the mean flow. It is shown that for high turbulence intensities a full theoretical reconstruction of the measured final droplet size distribution is possible from a probability density function of model Rayleigh–Taylor wavelengths ( ${\\it\\lambda}_{RT}$ ). In agreement with the literature (Varga et al. J. Fluid Mech. , vol. 497, 2003, pp. 405–434), mean droplet sizes are found to be equal to a mean theoretical Rayleigh–Taylor wavelength normalized by a particular constant value. This, however, is only true for local turbulence intensities less than ${\\sim}25\\,\\%$ , or for ratios of the turbulent Weber number to mean Weber number ( $\\mathit{We}^{\\prime }/\\mathit{We}$ ) of less than ${\\sim}6\\,\\%$ . Above this, the normalization value is no longer constant, but increases with $\\mathit{We}^{\\prime }/\\mathit{We}$ . Finally, the instability wavelengths can be used as part of an approximation that estimates the total number of objects formed after break-up, where the object number is found to be dictated by a balance of both mean flow conditions and local turbulence.
Publisher: IOP Publishing
Date: 18-10-2017
Publisher: Elsevier BV
Date: 06-2018
Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.IJPHARM.2022.122219
Abstract: This study aims to systematically isolate different anatomical features of the human pharynx with the goal to investigate their independent influence on airflow dynamics and particle deposition characteristics in a geometrically realistic human airway. Specifically, the effects of the uvula, epiglottis and soft palate on drug particle deposition are studied systematically, by carefully removing each of these anatomical features from reconstructed models based on MRI data and comparing them to a benchmark realistic airway model. Computational Fluid Dynamics using established turbulence models is employed to simulate the transport of mono-dispersed particles (3 µm) in the airway at two flow-rates. The simulations suggest three findings: 1) widening the space between the oral cavity and oropharynx and where the soft palate is situated leads to the most dramatic reduction in drug deposition in the upper airway 2) exclusion of the uvula and epiglottis: a) affects flow dynamics in the airway b) alters regional deposition behaviour c) does not significantly affect the total number of particles deposited in the pharynx and 3) the space adjacent to the soft palate is a key determinant for aerosol deposition in the extrathoracic region and is related to mechanisms of flow acceleration, ersion and recirculation.
Publisher: Elsevier BV
Date: 05-2022
Publisher: IOP Publishing
Date: 29-05-2020
Publisher: Elsevier BV
Date: 07-2016
Publisher: Elsevier BV
Date: 2020
Publisher: MDPI AG
Date: 02-04-2022
DOI: 10.3390/BIOENGINEERING9040150
Abstract: Developing novel drug formulations and progressing them to the clinical environment relies on preclinical in vitro studies and animal tests to evaluate efficacy and toxicity. However, these current techniques have failed to accurately predict the clinical success of new therapies with a high degree of certainty. The main reason for this failure is that conventional in vitro tissue models lack numerous physiological characteristics of human organs, such as biomechanical forces and biofluid flow. Moreover, animal models often fail to recapitulate the physiology, anatomy, and mechanisms of disease development in human. These shortfalls often lead to failure in drug development, with substantial time and money spent. To tackle this issue, organ-on-chip technology offers realistic in vitro human organ models that mimic the physiology of tissues, including biomechanical forces, stress, strain, cellular heterogeneity, and the interaction between multiple tissues and their simultaneous responses to a therapy. For the latter, complex networks of multiple-organ models are constructed together, known as multiple-organs-on-chip. Numerous studies have demonstrated successful application of organ-on-chips for drug testing, with results comparable to clinical outcomes. This review will summarize and critically evaluate these studies, with a focus on kidney, liver, and respiratory system-on-chip models, and will discuss their progress in their application as a preclinical drug-testing platform to determine in vitro drug toxicology, metabolism, and transport. Further, the advances in the design of these models for improving preclinical drug testing as well as the opportunities for future work will be discussed.
Publisher: Springer Science and Business Media LLC
Date: 25-02-2012
Publisher: Elsevier BV
Date: 10-2021
Publisher: American Chemical Society (ACS)
Date: 14-09-2021
Publisher: Springer Science and Business Media LLC
Date: 24-07-2014
Publisher: Elsevier BV
Date: 04-2023
Publisher: Springer Science and Business Media LLC
Date: 03-08-2013
Publisher: Elsevier BV
Date: 11-2012
Publisher: Elsevier BV
Date: 06-2012
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2010
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.IJPHARM.2019.118773
Abstract: Knowledge that enables the accurate simulation of drug deposition in the human upper airway is necessary to develop robust platforms for efficient drug delivery by inhalation devices. The human upper airway is deformable during inhalation but how it could affect the deposition of inhaled drugs is unknown. We aimed to determine whether pharyngeal deformation at the soft palate level would have any significant effects on throat deposition, in vitro lung dose and fine particle fraction. In this study, dry mannitol powders were delivered to the next-generation cascade impactor (NGI) through the United States Pharmacopeia (USP) throat, and a realistic upper airway cast (RUPAC) at flow rates of 40, 60 and 80 L min
Publisher: IOP Publishing
Date: 02-2019
Publisher: Elsevier BV
Date: 06-2013
Publisher: Cambridge University Press (CUP)
Date: 06-04-2020
DOI: 10.1017/JFM.2020.179
Publisher: Springer Science and Business Media LLC
Date: 26-03-2020
Publisher: University of Queensland Library
Date: 2020
Publisher: Springer International Publishing
Date: 2014
Publisher: Elsevier BV
Date: 02-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 06-2017
Publisher: Springer International Publishing
Date: 2014
Publisher: Elsevier BV
Date: 04-2019
Publisher: Cambridge University Press (CUP)
Date: 24-02-2012
DOI: 10.1017/JFM.2012.30
Abstract: The fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low ( ${\\mathit{Re}}_{E} = 1$ ) and high electric Reynolds numbers (up to ${\\mathit{Re}}_{E} = 120$ ). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\\ensuremath{\\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\\ensuremath{\\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.
Start Date: 2019
End Date: 12-2021
Amount: $484,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2020
End Date: 12-2023
Amount: $360,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2020
End Date: 12-2023
Amount: $463,597.00
Funder: Australian Research Council
View Funded ActivityStart Date: 07-2020
End Date: 12-2023
Amount: $363,152.00
Funder: Australian Research Council
View Funded ActivityStart Date: 04-2022
End Date: 04-2025
Amount: $495,000.00
Funder: Australian Research Council
View Funded Activity