ORCID Profile
0000-0002-2883-8329
Current Organisations
University of Sydney
,
The Hong Kong Polytechnic University
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Publisher: Springer Science and Business Media LLC
Date: 11-2007
DOI: 10.1007/BF03177442
Publisher: Elsevier BV
Date: 10-2001
Publisher: Elsevier BV
Date: 08-2001
Publisher: Elsevier BV
Date: 03-2012
Publisher: World Scientific Pub Co Pte Lt
Date: 05-2007
DOI: 10.1142/S0129183107010553
Abstract: The unsteady flow within a simplified 3D centrally-actuated type artificial heart was investigated numerically using moving boundary technique. The velocities on the inlet and outlet were determined according to the motion of the diaphragm. The case with heart beat rate of 75 beats per minute (bpm) was simulated. Two models were studied. It is found that, in the diastolic cycle, a vortex ring forms in the conjunction of the blood chamber and the inlet tube. This vortex ring can provide good wash-out on the wall.
Publisher: International Information and Engineering Technology Association
Date: 11-2017
Publisher: Springer Science and Business Media LLC
Date: 11-2007
DOI: 10.1007/BF03177448
Publisher: World Scientific Pub Co Pte Lt
Date: 20-12-2005
DOI: 10.1142/S0217984905009833
Abstract: The fluid flow and heat transfer in porous media has wide applications in oil industry and air conditioning system. In this study the momentum and energy transport processes in a porous medium are numerically simulated. The Brinkman-Forchheimer-extended Darcy equations and energy equation are solved using single lattice-Boltzmann method (LBM). As a first attempt, a benchmark problem is studied, i.e., momentum and energy transfer in a rectangular enclosure with differentially heated vertical walls. The effect of permeability on the critical Rayleigh numbers, the temperature distribution and flow field is discussed.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.JBIOMECH.2007.03.027
Abstract: One approach to tackle the particle deposition in human lungs in close proximity is to develop an understanding of the particle motion in bifurcation airways. Chronic obstructive pulmonary disease (COPD) is one of the most common diseases in humans. COPD always results in inflammation that leads to narrowing and obstructing of the airways. The obstructive airways can alter the respiratory flow and particle deposition significantly. In order to study the effect of obstruction on particle deposition, four three-dimensional four-generation lung models based on the 23-generation model of Weibel [1963. Morphometry of the Human Lung. New York Academic Press, Springer, Berlin.] have been generated. The fully three-dimensional incompressible laminar Navier-Stokes equations are solved using computational fluid dynamics (CFD) solver on structured hexahedral meshes. Subsequently, a symmetric four-generation airway model serves as the reference and the other three models are considered to be obstructed at each generation, respectively. The calculation results show that the obstructive airway has significant influence on the particle deposition down-stream of the obstruction. The skewed velocity profile in the bifurcation airway is modified by the throat consequently, more particles impact on the ider which results in higher deposition efficiency.
Publisher: Informa UK Limited
Date: 07-2006
Publisher: Elsevier BV
Date: 10-2009
Publisher: AIP Publishing
Date: 04-05-2012
DOI: 10.1063/1.4707744
Abstract: By using molecular dynamics simulation, we have investigated systematically the feasibility of continuous unidirectional water flux across a deformed single-walled carbon nanotube (SWNT) driven by an oscillating charge outside without osmotic pressure or hydrostatic drop. Simulation results indicate that the flux is dependent sensitively on the oscillating frequency of the charge, the distance of the charge from the SWNT, and the asymmetry of the water-SWNT system. A resonance-like phenomenon is found that the water flux is enhanced significantly when the period of the oscillation is close to twice the average hopping time of water molecules inside the SWNT. These findings are helpful in developing a novel design of efficient functional nanofluidic devices.
Publisher: World Scientific Pub Co Pte Lt
Date: 30-01-2009
DOI: 10.1142/S0217984909018114
Abstract: There are two conventional boundary treatment methods in molecular dynamics (MD) simulation for particle suspension or fiber in cross flow. One is that the fiber is represented by evenly spaced atoms, the other is that the fiber is treated as one mass point. The calculations with the two boundary treatment methods have been compared, it is found that, with the same properties, both methods could generate slip boundary condition on the fiber surface, however the one mass point method could result in very large slip boundary condition on the fiber surface, and the discrepancy could be as high as 2600%.
Publisher: Springer Science and Business Media LLC
Date: 03-04-2012
Publisher: Springer Science and Business Media LLC
Date: 14-06-2011
Abstract: Maintaining constant temperature is of particular importance to the normal operation of electronic devices. Aiming at the question, this paper proposes an optimum design of nanostructures made of high thermal conductive nanomaterials to provide outstanding heat dissipation from the confined interior (possibly nanosized) to the micro-spaces of electronic devices. The design incorporates a carbon nanocone for conducting heat from the interior to the exterior of a miniature electronic device, with the optimum diameter, D 0 , of the nanocone satisfying the relationship: D 0 2 ( x ) ∝ x 1/2 where x is the position along the length direction of the carbon nanocone. Branched structure made of single-walled carbon nanotubes (CNTs) are shown to be particularly suitable for the purpose. It was found that the total thermal resistance of a branched structure reaches a minimum when the diameter ratio, β* satisfies the relationship: β* = γ -0.25 b N -1 /k* , where γ is ratio of length, b = 0.3 to approximately 0.4 on the single-walled CNTs, b = 0.6 to approximately 0.8 on the multiwalled CNTs, k * = 2 and N is the bifurcation number ( N = 2, 3, 4 ...). The findings of this research provide a blueprint in designing miniaturized electronic devices with outstanding heat dissipation. PACS numbers: 44.10.+i, 44.05.+e, 66.70.-f, 61.48.De
Publisher: Elsevier BV
Date: 07-2003
DOI: 10.1016/S0021-9290(03)00064-2
Abstract: In a former paper, the inspiratory flow characteristics in a three-generation symmetric bifurcation airway have been numerically investigated using a control volume method to solve the fully three-dimensional laminar Navier-Stokes equations. The present paper extends the work to deal with asymmetric airway extracted from the 5th-11th branches of the model of Weibel (Morphometry of the Human Lung. New York Academic Press, Verlag, 1963) in order to more appropriately model human air passage. Computations are carried out in the Reynolds number range 200-1600, corresponding to mouth-air breathing rates ranging from 0.27 to 2.16l/s, representative for an averaged height man breathing from quiet to vigorous state. Particular attentions are paid to establishing relations between the Reynolds number and the overall flow characteristics, including flow patterns and pressure drop. The study shows that the ratios of airflow rate through the medial branches to that of their mother branches are the same, and this is also true for the ratios of airflow rate through the lateral branches. This partially explains why regular human breathing is not affected by airways of different sizes.
Publisher: Unpublished
Date: 2018
Publisher: Elsevier BV
Date: 2013
Publisher: AIP Publishing
Date: 04-09-2023
DOI: 10.1063/5.0159879
Publisher: AIP Publishing
Date: 09-2009
DOI: 10.1063/1.3204479
Abstract: A fractal analysis of effective thermal conductivity for unsaturated fractal porous media is presented based on the thermal-electrical analogy and statistical self-similarity of porous media. Here, we derive a dimensionless expression of effective thermal conductivity without any empirical constant. The effects of the parameters of fractal porous media on the dimensionless effective thermal conductivity are discussed. From this study, it is shown that, when the thermal conductivity of solid phase and wet phase are greater than that of the gas phase (viz., ks∕kg& , kw∕kg& ), the dimensionless effective thermal conductivity of unsaturated fractal porous media decreases with decreasing degree of saturation (Sw) and increasing fractal dimension for pore area (Df), fractal dimension for tortuosity (Dt), and porosity (ϕ) when the thermal conductivities of solid phase and wet phase are lower than that of the gas phase (viz., ks∕kg& , kw∕kg& ), the trends were just opposite. Our model was validated by comparing the model prediction with existing experimental data. Excellent agreement was found except for the cases at very low level of saturation.
Publisher: Springer Science and Business Media LLC
Date: 05-08-2012
Publisher: Springer Science and Business Media LLC
Date: 23-11-2000
DOI: 10.1007/PL00009638
Publisher: Springer Science and Business Media LLC
Date: 18-08-2020
Publisher: Springer Berlin Heidelberg
Date: 2011
Publisher: Springer Science and Business Media LLC
Date: 23-09-1999
Publisher: Springer Science and Business Media LLC
Date: 11-2002
Publisher: AIP Publishing
Date: 10-04-2023
DOI: 10.1063/5.0140569
Abstract: Due to a rapid decrease in fossil fuel resources and ever-growing carbon emissions, clean energy is urgently needed as a vital solution. In the past two decades, harvesting clean energy from ambient environment has attracted much attention. Flow induced vibration and energy harvesting performance of a cylinder with fins attached were investigated. Four configurations were studied: a plain cylinder, a cylinder with two windward fins, a cylinder with two leeward fins, and a cylinder with four fins. These four cylinders were tested in a water channel with a reduced velocity ranging between 2 and 25 and a Reynolds number ranging between 1500 and 11 400. It was found that the two-windward-fin cylinder underwent galloping, exhibiting much larger vibration litudes and a much broader operational velocity range, whereas the two-leeward-fin cylinder only underwent weak vortex-induced vibrations. By attaching both two windward and two leeward fins to the cylinder, a bi-directional flow-energy harvester was implemented, which outperformed the plain cylinder with much larger vibration litudes and a much broader velocity range. More importantly, due to the geometric symmetry, it is able to harvest flow energy from two opposite directions. A tuned-mass-d er system was then attached to the four-fin cylinder for the purpose of demonstration. Within the current flow speed range, the maximal voltage and power outputs are about 7.37 V and 1.81 μW, respectively, about 2.7 and 7.2 times the plain cylinder's peak values. The effects of flow incident angle and fin length were also studied. Numerical simulations were also conducted to provide a detailed information of flow and pressure to uncover the underlying physics. This bi-directional flow-energy harvester is a suitable candidate to operate at sites where the flow periodically switches its directions, such as in tidal flows.
Publisher: Elsevier BV
Date: 05-2005
Publisher: AIP Publishing
Date: 08-2023
DOI: 10.1063/5.0160114
Abstract: A circular cylinder attached by a rigid splitter plate of different lengths was tested to examine its effects on the control of flow-induced vibration. Tests were carried out in a closed-loop water channel. A cylinder of diameter D = 20 mm and a mass ratio m* ≈ 50 was installed to oscillate in the transverse direction. A wide range of splitter length was considered, i.e., L/D = 0–3.5, at a range of reduced velocity Ur = 1–25 and the Reynolds number Re = 800–11 000. Numerical simulations were also conducted to reveal the flow structures associated with the vibration modes observed in the experiment. It is found that, as L/D increases from 0 to 0.25, the peak value of cylinder oscillation litude increases and appears at higher reduced velocities. When the splitter length continues to rise, galloping-type oscillations occur at L/D = 0.5 and 0.75. The transition stage has been found at L/D = 1.0. Oscillation is then significantly suppressed when the splitter length is larger than L/D = 1.5.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.JBIOMECH.2007.01.008
Abstract: A numerical method is developed to solve the fluid-structure interaction in three-dimensional pulmonary arterial bifurcation with collapsible tubes. A self-developed FEM code is used to calculate the nonlinear deformation of the thin-walled structure and a commercial CFD solver, FLUENT, is used to resolve the fluid flow. The large deformation of the structure alters the flow field significantly while the fluid pressure affects the deformation of the structure strongly. In the bifurcation branches, the relatively short tube collapses into wave number N=3 mode. The strong collapse of the branch tube leads to a large contraction of the cross-sectional area and increases the resistance on the fluid flow. The recirculation occurs at both the up- and down-stream of the collapsed tube.
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Publisher: Elsevier BV
Date: 04-2017
Publisher: American Physical Society (APS)
Date: 27-10-2008
Publisher: Elsevier BV
Date: 04-2005
Publisher: ASMEDC
Date: 2002
Abstract: It is known that a splitter plate can moderate the vortex formation behind a cylinder, and consequently the vibration behavior of the cylinder and the plate. This paper uses the standard k-ε model and a modified wall function to simulate the flow-induced vibration of a 2D cylinder-plate system in a cross flow. Good agreement between available measurements and calculations is obtained for a single cylinder in a cross flow at Reynolds numbers up to 105. The flow-induced vibration of a cylinder-plate system in a cross flow is attempted using the same numerical method. It is possible to replicate the vibration behavior for the cylinder and the splitter plate, even though quantitative agreement with measurements is not obtained.
Publisher: Springer Berlin Heidelberg
Date: 18-12-2016
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.JTBI.2008.03.016
Abstract: Although recent investigations [Ryan, M.G., Yoder, B.J., 1997. Hydraulic limits to tree height and tree growth. Bioscience 47, 235-242 Koch, G.W., Sillett, S.C.,Jennings, G.M.,Davis, S.D., 2004. The limits to tree height. Nature 428, 851-854 Niklas, K.J., Spatz, H., 2004. Growth and hydraulic (not mechanical) constraints govern the scaling of tree height and mass. Proc. Natl Acad. Sci. 101, 15661-15663 Ryan, M.G., Phillips, N., Bond, B.J., 2006. Hydraulic limitation hypothesis revisited. Plant Cell Environ. 29, 367-381 Niklas, K.J., 2007. Maximum plant height and the biophysical factors that limit it. Tree Physiol. 27, 433-440 Burgess, S.S.O., Dawson, T.E., 2007. Predicting the limits to tree height using statistical regressions of leaf traits. New Phytol. 174, 626-636] suggested that the hydraulic limitation hypothesis (HLH) is the most plausible theory to explain the biophysical limits to maximum tree height and the decline in tree growth rate with age, the analysis is largely qualitative or based on statistical regression. Here we present an integrated biophysical model based on the principle that trees develop physiological compensations (e.g. the declined leaf water potential and the tapering of conduits with heights [West, G.B., Brown, J.H., Enquist, B.J., 1999. A general model for the structure and allometry of plant vascular systems. Nature 400, 664-667]) to resist the increasing water stress with height, the classical HLH and the biochemical limitations on photosynthesis [von Caemmerer, S., 2000. Biochemical Models of Leaf Photosynthesis. CSIRO Publishing, Australia]. The model has been applied to the tallest trees in the world (viz. Coast redwood (Sequoia sempervirens)). Xylem water potential, leaf carbon isotope composition, leaf mass to area ratio at different heights derived from the model show good agreements with the experimental measurements of Koch et al. [2004. The limits to tree height. Nature 428, 851-854]. The model also well explains the universal trend of declining growth rate with age.
Publisher: Springer Science and Business Media LLC
Date: 12-03-2010
DOI: 10.1007/S10237-010-0202-1
Abstract: It has been found that both circulating blood cells and tumor cells are more easily adherent to curved microvessels than straight ones. This motivated us to investigate numerically the effect of the curvature of the curved vessel on cell adhesion. In this study, the fluid dynamics was carried out by the lattice Boltzmann method (LBM), and the cell dynamics was governed by the Newton's law of translation and rotation. The adhesive dynamics model involved the effect of receptor-ligand bonds between circulating cells and endothelial cells (ECs). It is found that the curved vessel would increase the simultaneous bond number, and the probability of cell adhesion is increased consequently. The interaction between traveling cells would also affect the cell adhesion significantly. For two-cell case, the simultaneous bond number of the rear cell is increased significantly, and the curvature of microvessel further enhances the probability of cell adhesion.
Publisher: Elsevier BV
Date: 07-2008
Publisher: Springer Science and Business Media LLC
Date: 23-12-2016
DOI: 10.1038/SREP39410
Abstract: Gas detection with hollow-core photonic bandgap fibre (HC-PBF) and pulsed photothermal (PT) interferometry spectroscopy are studied theoretically and experimentally. A theoretical model is developed and used to compute the gas-absorption-induced temperature and phase modulation in a HC-PBF filled with low-concentration of C 2 H 2 in nitrogen. The PT phase modulation dynamics for different pulse duration, peak power and energy of pump beam are numerically modelled, which are supported by the experimental results obtained around the P(9) absorption line of C 2 H 2 at 1530.371 nm. Thermal conduction is identified as the main process responsible for the phase modulation dynamics. For a constant peak pump power level, the phase modulation is found to increase with pulse duration up to ~1.2 μs, while it increases with decreasing pulse duration for a constant pulse energy. It is theoretically possible to achieve ppb level detection of C 2 H 2 with ~1 m length HC-PBF and a pump beam with ~10 ns pulse duration and ~100 nJ pulse energy.
Publisher: IOP Publishing
Date: 23-02-2009
Publisher: Springer Science and Business Media LLC
Date: 09-2007
DOI: 10.1007/BF03177427
Publisher: World Scientific Pub Co Pte Lt
Date: 06-2006
DOI: 10.1142/S0129183106009291
Abstract: The natural convection problem in a square cavity filled with heterogeneously porous medium is solved by lattice Boltzmann method. The temperature distribution is fully coupled with the fluid velocity through relaxation time. The present calculated results are in good agreement with available published data. It is found that the porosity of porous media near the walls has significant influence on the heat transfer, and the porosity of middle porous medium has little influence on the natural convection. It is of particular interest for thermal management in electronic packages, since it can reduce the space of air.
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.JTBI.2007.06.020
Abstract: Penguins, mostly live in the extremely cold Antarctic, are known to have feathers and down, which are light weight, compact and extremely efficient in preventing heat loss. Nevertheless, the mechanisms of heat transfer through the penguin feathers and down, and how the unique characteristics of penguin feathers and down make them such good thermal insulators are not fully understood. In this paper, an integrated model of heat transfer through the penguin feathers and down is developed and computed using finite volume method, with the geometrical structure of the barbules being considered. Monte-Carlo method is adopted to determine the radiative absorption and emission constant in the integrated model. The effective thermal conductance of penguin feathers and down computed from our model compared well with the experimentally measured value reported in the literature. Three models (penguin model, random fibre model (fibre radius=3microm) and random fibre model (fibre radius=10microm)) are further simulated and compared. Results showed that the relative small radius of the barbules of penguin feather and their geometrical structure are responsible for the reduction of heat loss in cold environment.
Publisher: Wiley
Date: 30-08-2018
DOI: 10.1111/BCPT.13100
Publisher: IEEE
Date: 09-2010
Publisher: American Chemical Society (ACS)
Date: 13-09-2013
DOI: 10.1021/JP405036C
Abstract: The directed transport of water molecules in a single-walled carbon nanotube (SWNT) based on a ratchet effect is investigated by molecular dynamics simulations. The system is driven far away from thermal equilibrium by an additional deterministic perturbation of a vibrating charge, and the spatial inversion symmetry is broken by the continuous deformations of the SWNT. It is well-known that the water flux across a circular channel decreases when the channel is narrowed or deformed. However, our simulation results show that the water flux almost increases linearly within a deformation of 1.9 Å. There exists an optimized value of deformation at which the pumping capacity takes its maximum value. Moreover, the direction of transport even exhibits a change of sign with narrowing the carbon nanotube.
Publisher: Springer Science and Business Media LLC
Date: 15-04-2016
Publisher: Elsevier BV
Date: 08-2008
DOI: 10.1016/J.JBIOMECH.2008.06.018
Abstract: The inspiratory flow characteristics in a CT-scanned human lung model were numerically investigated using low Reynolds number (LRN) kappa-omega turbulent model. The five-generation airway is extracted from the trachea to segmental bronchi of a 60-year-old Chinese male patient. Computations were carried out in the Reynolds number range of 900-2100, corresponding to mouth-air breathing rates of 190-440 ml/s. Flow patterns on the Re=2100 and flow rate distribution were presented. In this model, the flow pattern is very complex. To count the effect of laryngeal jet on trachea inlet, the trachea was extended and modified to simulate the larynx, consequently the inlet velocity profile is biased towards the rear wall. In the inferior lobar bronchi, there are two stems in which the axial velocity is stronger but secondary velocity is weaker. Secondary flow in the lateral bronchi is stronger than the medial ones. With increasing Re, the air flow increases in the middle, inferior lobes and left main bronchus, i.e., flow biases to left and downward.
Publisher: Springer International Publishing
Date: 2018
DOI: 10.1007/978-3-319-96445-4_12
Abstract: The blood flow behaviors in the microvessels determine the transport modes and further affect the metastasis of circulating tumor cells (CTCs). Much biochemical and biological efforts have been made on CTC metastasis however, precise experimental measurement and accurate theoretical prediction on its mechanical mechanism are limited. To complement these, numerical modeling of a CTC extravasation from the blood circulation, including the steps of adhesion and transmigration, is discussed in this chapter. The results demonstrate that CTCs prefer to adhere at the positive curvature of curved microvessels, which is attributed to the positive wall shear stress/gradient. Then, the effects of particulate nature of blood on CTC adhesion are investigated and are found to be significant in the microvessels. Furthermore, the presence of red blood cell (RBC) aggregates is also found to promote the CTC adhesion by providing an additional wall-directed force. Finally, a single cell passing through a narrow slit, mimicking CTC transmigration, was examined under the effects of cell deformability. It showed that the cell shape and surface area increase play a more important role than the cell elasticity in cell transit across the narrow slit.
Publisher: American Physical Society (APS)
Date: 18-06-2020
Publisher: Informa UK Limited
Date: 08-1997
Publisher: American Society of Mechanical Engineers
Date: 22-06-2011
Abstract: Obstructive sleep apnea (OSA) is very common and can strike anyone at any age, even children. Yet still because of the lack of awareness by the public and healthcare professionals, the majority remain undiagnosed and therefore untreated, despite the fact that this serious disorder can have significant consequences. Untreated, sleep apnea can cause high blood pressure and other cardiovascular disease, memory problems, weight gain, impotency, and headaches [1]. OSA is caused by a blockage of the airway, usually when the soft tissue in the rear of the throat collapses and closes during sleep. With apnea event, the brain briefly arouses people with sleep apnea in order for them to resume breathing, but consequently sleep is extremely fragmented and of poor quality. Several surgical techniques may be used for OSA, and these include: uvulopalatopharngeoplasty (UP3), tonsillectomy and pharyngoplasty, uvulopalatal flap, laser and radiofrequency assisted uvulopalatal surgeries. The surgery involves removing the uvula and some of the surrounding soft palate. The idea behind the upper airway surgery is to eliminate the area of obstruction or to widen the airway so it does not occlude completely. However, the success rate is limited for ex le, the UP3 helps in around 50% who have the surgery and in others it does not help at all or it helps only partially [2]. The post-operative complications after surgery are often the result of a dilemma during the operation of how much tissue to resect: too little is ineffective, yet too much may leave a patient with speech impedance and palatal stenosis, which can make OSA worse [3]. Therefore, accurate prediction of tissue reduction for this treatment is urgently needed.
Publisher: World Scientific Pub Co Pte Lt
Date: 30-10-2008
DOI: 10.1142/S0217984908017229
Abstract: The effect of channel width on the density structure of confined fluid in the nano-/micro-channels is examined by equilibrium molecular dynamics (EMD) simulation. It was found that the density oscillation occurs near the wall in both cases of the macroscale or nanoscale confined flow. There exists a threshold channel width L threshold , when channel width H L threshold , density oscillates throughout the channel. When H L threshold , L threshold is constant and about 5–6 molecular diameter long, and the density becomes uniform beyond this threshold layer. A newly defined ch number may serve to be the parameter to compare similarity in the micro-/nano-scale channel flow. Moreover, the effect of the density oscillation on fluid mass flux rate is examined quantitatively. The result shows that the effect should be considered when the channel width is below 5 molecular diameter.
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier BV
Date: 10-2010
Publisher: Elsevier BV
Date: 04-2017
Publisher: Informa UK Limited
Date: 03-1997
Publisher: Springer Science and Business Media LLC
Date: 12-1996
DOI: 10.1007/BF00350251
Publisher: IOP Publishing
Date: 28-09-2007
Publisher: Elsevier BV
Date: 05-2008
DOI: 10.1016/J.BIORTECH.2007.05.038
Abstract: Based on the ideal biofilter model, numerical simulation using lattice Boltzmann method is carried out to investigate the effect of Darcy number and porosity on removal efficiency of low headloss biofilter. The generalized Navier-Stokes model (Brinkman-Forchheimer-extended Darcy model) is applied making several assumptions. It is found that the Darcy number has determinant influence on the removal efficiency, and the effect of porosity on removal efficiency is very weak at lower Darcy numbers but very strong at higher Darcy numbers. It was found there was strong evidence of flow heterogeneity in the biofilter (Chitwood, D.E., Devinny, J.S., Reynolds Jr., F.E., 1999. Evaluation of a two-stage biofilter for treatment of POTW waste air. Environ. Prog. 18, 212-221). In this study we have found the biofilter performance can be improved by adjusting local Darcy number of the porous media in the biofilter.
Publisher: The Electrochemical Society
Date: 2006
DOI: 10.1149/1.2164807
Publisher: American Physical Society (APS)
Date: 24-11-2015
Publisher: Elsevier BV
Date: 08-2019
Publisher: Elsevier BV
Date: 11-2006
Publisher: Trans Tech Publications, Ltd.
Date: 03-2009
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.614.235
Abstract: A well-aligned titania nanotube array grown on titanium sheet was fabricated by an anodization process in hydrofluoric acid-phosphoric acid-ethylene glycol aqueous electrolyte. Electroactive ruthenium oxide was filled into independent titania nanotubes or deposited on the surface of planar titanium sheet by an electrodeposition-oxidation process. Electrochemical capacitances of these well-designed ruthenium oxides were investigated for supercapacitor applications. Accordingly, ruthenium oxide-titania/titanium (RuO2-TiO2/Ti) nanocomposite exhibits a much higher specific capacitance, power and energy density than ruthenium oxide/titanium (RuO2/Ti) in sulphate acid electrolyte. The utilization efficiency of RuO2 is intensively improved by introducing a novel electrode substrate with a nanotube array structure. Such a superior performance of RuO2-TiO2/Ti nanocomposite is ascribed to its highly accessible reaction sites of well-tailored RuO2 on TiO2 nanotubes.
Publisher: Elsevier BV
Date: 06-2020
Publisher: World Scientific Pub Co Pte Lt
Date: 20-12-2005
DOI: 10.1142/S0217984905010116
Abstract: One of the functions of microvilli in the microvessel endothelial glycocalyx is molecular filtering. The microvillus behaves as a mechanosensory system which may sense the fluid shear and drag forces. The permeability of small particles in microvessel is crucial for drug design and drug delivery. Therefore a better understanding of flow field around microvillus is important to simulate accurately the particle penetration in microvessel. Since the dimension of the microvilli is about ~10 nm , the conventional Navier-Stokes equation may not be good enough to simulate the fluid flow in such microscale and nanoscale structures. Molecular dynamics (MD) simulation is a powerful method to simulate the fluid flow at the molecular level. As a first attempt, the microvillus is reduced as a two-dimensional cylinder which is in a cross flow. The detailed drag and lift together with flow field are obtained and compared with available data.
Publisher: ASMEDC
Date: 2011
DOI: 10.1115/FUELCELL2011-54927
Abstract: Based on models of a porous electrode, a more accurate lattice Boltzmann model for simulating the performance of a solid oxide fuel cell (SOFC) is proposed. The fuel is pure Carbon monoxide and the flow in the SOFC is steady. Results show good agreement between simulated and measured data. The accuracy of concentration overpotential prediction is crucial for low reactant concentrations. The addition of a small amount of air to the fuel yields fully stable performance without measurable carbon deposits detected on the catalyst layer or the fuel cell. Cell performance increases with the temperature. As a first test of the model, a benchmark problem regarding the performance of an internal reforming solid oxide fuel cell (IR-SOFC) is investigated. When the catalyst activity decreases, the rate of methane conversion decreases near the reactor entrance and thus the temperature profile is smoother. This phenomenon is termed methane slippage.
Publisher: American Physical Society (APS)
Date: 16-06-2011
Publisher: AIP Publishing
Date: 23-06-2008
DOI: 10.1063/1.2940597
Abstract: Ω -shaped copper specimens are oxidized in wet air. The results show that totally no-wire structure, CuO whiskers, and the high density of well-aligned CuO nanowires can be formed simultaneously on the different positions of the specimen. A three-dimensional flow simulation results indicate that the direction of velocity vectors of local gas flow affects the alignment of nanowires during oxidation while the shear stress of flowing gas near the surface of a Ω-shaped specimen controls the density of nanowires.
Publisher: Elsevier BV
Date: 07-2012
Publisher: IOP Publishing
Date: 05-2010
Publisher: Hindawi Limited
Date: 07-05-2021
DOI: 10.1155/2021/6683828
Abstract: Obstructive sleep apnea (OSA) is a common disorder which may need to be treated by the upper respiratory tract (URT) surgery. To increase the success rate of the URT surgery, it is crucial to understand the flow features in the URT models. In this work, the turbulent flow characteristics in four 3D anatomically accurate URT models reconstructed from two OSA subjects with successful and failed surgery are numerically studied by the large-eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS). The features of velocity fields, pressure fields, and wall shear stress fields as well as the spectral analysis of wall shear stress between successful and failed surgery are explored. The results indicate that LES is capable of capturing flow patterns and flow oscillation and is effective for OSA surgery prediction. Even if the unsteady RANS can obtain the correct pressure drop across the airways, it may not be appropriate to be used for surgery prediction. Moreover, it is found that the quality of oscillating signal of wall shear stress is a key factor in surgery prediction. In a successful surgery, the wall shear stress oscillation is always strong, and the oscillating signal can perform a dominant frequency near 3~5 Hz, while in a failed surgery it does not show this clear intrinsic property. The results not only will gain new insights in the URT surgical planning but also will improve the prediction of surgical outcome for OSA patients.
Publisher: Elsevier BV
Date: 08-2016
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 09-2003
Publisher: Springer Berlin Heidelberg
Date: 2014
Publisher: Springer Netherlands
Date: 2003
Publisher: American Chemical Society (ACS)
Date: 13-02-2018
DOI: 10.1021/ACS.LANGMUIR.7B04162
Abstract: Controlling the motion of liquid drops on the solid surface has broad technological implications. In this study, the many-body dissipative particle dynamics (MDPD) was employed to study the drop behaviors on chemical chessboard-patterned surfaces formed by square or triangular tiles. The scaling relationship of the model was established based on the surface tension, viscosity, and density of a real fluid, and an improved contact angle measurement technique was introduced to the MDPD system. For drops on a horizontal plane with different tile sizes, the equilibrium morphology was examined. The critical Bond number, that is, the critical dimensionless force which is required to unpin the drop, was found strongly affected by the size and the shape of the tiles. Once the droplet begins to move, the tile pattern and the size strongly affect the velocity fluctuation while weakly affect the average velocity. Interestingly, besides the common straight forward path, two more route patterns (zigzag and oblique) were observed by only tuning the tile angle, indicating that the advancing routes of the drop may vary according to the tile angle. To the author's knowledge, this phenomenon has not been reported in the literature. This study provides a valuable tool to explore the possibility of passive control of the drop's motion by energy-free chemical heterogeneous surfaces and thus is helpful for engineers to design a surface that could manipulate the drop motion without external energy.
Publisher: Elsevier BV
Date: 08-2009
DOI: 10.1016/J.JBIOMECH.2009.05.004
Abstract: The particle deposition in a computerized tomography (CT)-scanned human lung was numerically investigated. The five-generation airway is extracted from the trachea to segmental bronchi of a 60-year-old Chinese male patient. Computations were carried out in the flow rate range of 210-630 ml/s (Reynolds number range of 1000-3000) and particle size of 2-10 microm (Stokes number range of 0.0007-0.049). To count the effect of laryngeal jet on trachea inlet, the trachea was extended and modified to simulate the larynx, consequently the inlet velocity profile is biased towards the rear wall. The laryngeal jet-induced turbulence was simulated using low Reynolds number (LRN) kappa-omega turbulent model. Particle deposition patterns, deposition efficiency and deposition factor were studied in detail. The turbulent flow has significant effect on the particle deposition, and the present deposition factor is compared well with the available data.
Publisher: Springer Science and Business Media LLC
Date: 29-06-2019
DOI: 10.1007/S10237-019-01192-8
Abstract: An explicit immersed boundary-lattice Boltzmann method is applied to numerically investigate the dynamics of primary cilium in pulsatile blood flows with two-way fluid-structure interaction considered. To well characterize the effect of cilium basal body on cilium dynamics, the cilium base is modeled as a nonlinear rotational spring attached to the cilium's basal end as proposed by Resnick (Biophys J 109:18-25, 2015. 0.1016/j.bpj.2015.05.031). After several careful validations, the fluid-cilium interaction system is investigated in detail at various pulsatile flow conditions that are characterized by peak Reynolds numbers ([Formula: see text]) and Womersley numbers ([Formula: see text]). The periodic flapping of primary cilium observed in our simulations is very similar to the in vivo ciliary oscillation captured by O'Connor et al. (Cilia 2:8, 2013. 0.1186/2046-2530-2-8). The cilium's dynamics is found to be closely related to the [Formula: see text] and [Formula: see text]. Increase the [Formula: see text] or decrease the [Formula: see text] bring to an increase in the cilium's flapping litude, tip angular speed, basal rotation, and maximum tensile stress. It is also demonstrated that by reducing the [Formula: see text] or enhancing the [Formula: see text] to a certain level, one can shift the flapping pattern of cilium from its original two-side one to a one-side one, making the stretch only happen on one particular side. During the flapping process, the location of the maximum tensile stress is not always found at the basal region instead, it is able to propagate from time to time within a certain distance to the base. Due to the obstruction of the primary cilium, the distribution of wall shear stress no longer remains uniform as in the absence of cilia. It oscillates in space with the minimum magnitude which is always found near where the cilium is located. The presence of cilium also reduces the overall level of wall shear stress, especially at the region near the cilium's anchor point.
Publisher: Unpublished
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 04-10-2016
DOI: 10.1007/S12013-016-0765-2
Abstract: The motion of two red blood cells in a stenosed microvessel was simulated using dissipative particle dynamics. The effects of intercellular interaction, red blood cell deformability and the initial cell orientation on the deformation and aggregation of the RBCs and on the flow resistance were investigated. The red blood cell membrane was treated as a three-dimensional coarse-grained network model and the intercellular interaction was modeled by the Morse potential based on a depletion-mediated assumption. It is shown that the flow resistance increases dramatically when the red blood cells enter into the stenosis and decreases rapidly as RBCs move away from the stenosis. Particularly, for a pair of stiffer red blood cells with the initial inclination angle of 90°, the maximum value of the flow resistance is larger while a higher flow resistance can also come from a stronger aggregation. For a pair of stiffer red blood cells moving parallel to the main flow, when their positions are closer to the vessel wall at the upstream of the stenosis, the flow resistance increases due to the migration to the vessel center at the stenosis. In addition, for a pair of red blood cells with the initial inclination angle of 0°, the flow resistance from the aggregate formed by a pair of red blood cells with a larger deformation is higher.
Publisher: Society for Imaging Science & Technology
Date: 03-2006
Publisher: IOP Publishing
Date: 05-2012
Publisher: Elsevier
Date: 2013
Publisher: Elsevier BV
Date: 04-2008
Publisher: Elsevier BV
Date: 07-2018
Publisher: Springer Science and Business Media LLC
Date: 24-07-2014
Publisher: Elsevier BV
Date: 2011
Publisher: Trans Tech Publications, Ltd.
Date: 24-10-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.110-116.4269
Abstract: The effect of the wavy surface on the aerodynamic characteristics of an airfoil is studied using the large eddy simulations. A more gentle lift characteristic is obtained during stall. For angles of attack less than the baseline stall angle of a NACA0012 airfoil, a lift coefficient reduction was observed for the wavy airfoils, while the lift coefficient increases up to 23% greater than that of a NACA0012 airfoil when the angle of attack is larger than the baseline stall angle of the NACA0012 airfoil.
Publisher: Springer Science and Business Media LLC
Date: 12-10-2009
DOI: 10.1007/S10544-008-9241-0
Abstract: Mixing of analytes and reagents in microfluidic devices is often crucial to the effective functioning of lab-on-a-chip. It is possible to affect the mixing in microfluidics by intelligently controlling the thermodynamic and chemical properties of the substrate surface. Numerous studies have shown that the phase behavior of mixtures is significantly affected by surface properties of microfluidics. For ex le, the phase separation between the fluids can be affected by heterogeneous patterns on the substrate. The patterned substrate can offer an effective means to control fluid behavior and in turn to enhance mixing. The golden mean is a ratio that is present in the growth patterns of many biological systems--the spiral formed by a shell or the curve of a fern, for ex le. The golden mean or golden section was derived by the ancient Greeks. Like "pi" the golden mean ratio is an irrational number 1.618, or (square root{5} + 1) / 2. It was found that the golden mean was an optimum ratio in natural convection heat transfer problem (Liu and Phan-Thien, Numer Heat Transf 37:613-630, 2000). In this study, we numerically studied the effect of optimum surface pattern on mixing in a micro channel and found that the flow oscillation and chaotic mixing were enhanced apparently when the ratio of hydrophobic and hydrophilic boundary follows the golden mean.
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 05-2013
Publisher: ASMEDC
Date: 2002
Abstract: This paper describes a numerical technique that can prevent the mesh from severe distortion in flow-induced vibration calculations. An orthogonal transformed space that is related to the physical space through a Laplacian equation is introduced. At each time step, the mesh may deform significantly in the physical space due to structural vibration, but the mesh nodal value in the transformed space remains constant. As long as the coordinates in the physical space can be adjusted to render the transformed space independent of time, the mesh shape in the physical space is preserved, even though the mesh area may enlarge or reduce significantly. For simplicity, a two-dimensional flow-induced vibration problem is used to illustrate this method. Two side-by-side elastic cylinders in a cross flow are considered. The Reynolds number is fixed at 200 so that a laminar wake is still available. The mass ratio is chosen to be small so that large displacements of the cylinders can be realized. The predictions with and without mesh preservation are compared. The difference between the two results could be as large as 25% in the prediction of the mean transverse displacements of the cylinders. The method could be extended to three-dimensional flow-induced vibration problems without much difficulty.
Publisher: Cold Spring Harbor Laboratory
Date: 23-04-2017
DOI: 10.1101/129841
Abstract: The pathways of signaling molecules are important to understanding how signaling molecules regulate physiological function and also in predicting the pathological development which is important to therapeutic strategy, however the thorough knowledge of these pathways is still lack. In this paper, we used the big data concept to analyze the pathways of signaling molecules and categorize these molecules into five groups according to their origin and effect on the five organs of heart-spleen-lung-kidney-liver. Heart group includes IGF, Ang and Mg spleen group includes ANP, aldosterone, retinoic acid and ghrelin lung group includes FGF7, VEGF, ascorbic acid and HIF kidney group includes calcitonin, PTHrP, Wnt and NO and liver group includes EPO, renin, SOD, AKR and GSH. We found that each group of molecules have assisting effect on the other organ in the order of heart-spleen-lung-kidney-liver-heart, and have regulating effect on the other organ in the order of heart-lung-liver-spleen-kidney-heart. Moreover, the pathways of molecules of each group also follow these two arrangements, in which the pathways of molecules form a closed-loop that may lead to new therapeutic strategies.
Publisher: The Royal Society
Date: 07-2016
Abstract: The active manipulation of a turbulent round jet is experimentally investigated based on the injection of two radial unsteady minijets, prior to the issue of the main jet. The parametric study is conducted for the mass flow ratio C m of the minijets to the main jet, and the ratio f e / f 0 of the minijet frequency to the preferred-mode frequency of the main jet. It is found that the decay rate of the jet centreline mean velocity could be greatly increased if the two minijets are separated azimuthally by an angle θ =60°, instead of by θ =180°. This increase is a consequence of the flapping motion of the jet column, and the formation process and generation mechanism of this flapping motion are unveiled by careful analysis of the experimental data.
Publisher: Elsevier BV
Date: 04-2002
DOI: 10.1016/S0021-9290(01)00225-1
Abstract: The inspiratory flow characteristics in a three-generation lung airway have been numerically investigated using a control volume method to solve the fully three-dimensional laminar Navier-Stokes equations. The three-generation airway is extracted from the fifth to seventh branches of the model of Weibel (Morphometry of the Human Lung, Academic Press, New York, Springer, Berlin, 1963) with in-plane and 90 degrees off-plane configurations. Computations are carried out in the Reynolds number range of 200-1600, corresponding to mouth-air breathing rates ranging from 0.27 to 2.16l/s, or an averaged height of a man breathing from quiet to vigorous state. Particular attention is paid to establishing relations between the Reynolds number and the overall flow characteristics, including flow patterns and pressure drop. The ratio of airflow rate through the medial branch to that of the lateral branch for an in-plane airway increases as Re(0.227). However, the total pressure drop coefficient varies as Re(-0.497) for an in-plane airway and as Re(-0.464) for an off-plane airway. These pressure drop results are in good agreement with the experimentally measured behavior of Re(-0.5) and are more accurate than the numerically determined behavior of Re(-0.61) assuming the airways to be approximated by two-dimensional channels.
Publisher: Informa UK Limited
Date: 18-10-2017
Publisher: American Society of Mechanical Engineers
Date: 22-06-2011
Abstract: Haematopoietic stem cells (HSCs) circulate in the bloodstream under flow conditions, but the mechanical mechanisms of governing their physiological trafficking in mammals are still not yet clearly understood. The mobilization of HSCs and their progenitors into the circulation represents the basis for modern bone marrow transplantation procedures [1]. Recently, Mendez-Ferrer et al. performed experimental investigations on mice [2]. They demonstrated that the circulating HSCs and their progenitors exhibit robust circadian oscillations, and the circadian fluctuations could also be significantly altered when the HSCs were subjected to different time of lighting. These results indicated that the photic cues could affect the trafficking of HSCs in healthy animals. This implies that the light is the stimulus of HSCs release. When the HSCs are exposed to light, the HSCs release would markedly increase when the HSCs are in darkness, the HSCs release keeps low efficiency. In this study, we numerically simulate this phenomenon to study the mechanical mechanism of circadian fluctuations regulated HSCs release under the influence of periodic lighting time.
Publisher: Elsevier BV
Date: 07-2019
Publisher: Informa UK Limited
Date: 08-07-2016
Publisher: IOP Publishing
Date: 11-2010
Publisher: Informa UK Limited
Date: 12-05-2000
Publisher: Springer Netherlands
Date: 2008
Publisher: ASMEDC
Date: 2002
Abstract: The numerical method developed previously to analyze two-dimensional vortex-blade interaction problems is validated using recently measured vortex-induced blade vibration data. It assumed a vortex lattice method to calculate the flow field assuming a distribution of sources and discrete vortices on the blade surfaces and a free wake model for the wake flow. A discrete vortex tracking technique in Lagrangian frame is used to track the path of the vortices. The blade is modeled as elastic structures with two-degree-of-freedom in plunging and pitching direction. The fully coupled fluid-structure interaction problem is resolved by means of a time-marching technique. The flow-field is assumed to be inviscid, incompressible and two-dimensional, with no flow separation occurring on the surfaces of the blade. Two cases were examined and they included a blade-vortex interaction and a blade vortex street interaction problem. In the blade-vortex interaction case, the blade is modeled as rigid therefore, the response of the structure is purely aerodynamics. The calculated variation of the lift coefficient of the blade with the horizontal missed distance of the convected vortex compares well with known experimental results. In the blade vortex street interaction case, the blade is modeled as elastic and is under the unsteady excitation from a Karman vortex street. The calculated blade responses due to vortex-induced vibration are compared with some recently measured vibration characteristics of a flat plate placed behind a cylinder at different separation distance. Good agreement between calculations and measured vibration litudes of the plate at its mid-span is obtained, thus indicating that the numerical method gives a viable model for the analysis of the aerodynamics and structural response in vortex/blade interaction problems.
Publisher: Elsevier BV
Date: 05-2001
Publisher: Elsevier BV
Date: 08-2016
Publisher: ASMEDC
Date: 2002
Abstract: Two staggered elastic cylinders in a cross flow have been numerically studied. The inclined angles change from 0° to 90° at 15° degree interval while the spacing ratio is maintained at 1.5. The two cylinders are mounted at the ends and are free to move under the action of the unsteady flow-induced forces. The present approach solves the flow field using a finite element method and models the cylinder motions using a two-degree-of-freedom structural dynamics model. Two different cases are considered one is the rigid case where the cylinders are still, and the other is the elastic case where the cylinders undergo oscillations. Good agreement for the rigid case is obtained between the present 2-D calculations and the previously published data. The investigation also examines the influence of the inclined angle on the vibrations of the cylinders and their spectral analysis.
Publisher: World Scientific Pub Co Pte Lt
Date: 30-01-2009
DOI: 10.1142/S0217984909018187
Abstract: Based on the models of the porous-electrode, a lattice Boltzmann model of a solid oxide fuel cell is presented, which allows the computation of the local distributions of the electrical potential, current density, and concentration of the chemical species. The physics of the cell and the simplifying assumptions are presented a sketch of the numerical procedure is also given. The numerical results obtained with hydrogen as the fuel are compared with results from other simulation codes which were developed for a planar geometry. The numerical results show that the counter-flow design as being the most efficient. Furthermore, and with increasing the percent H 2 in the fuel stream, the voltage drops profile alters from precipitous to gentle. These results are excellent.
Publisher: Elsevier BV
Date: 2012
Publisher: Unpublished
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 13-10-2017
Publisher: Japan Society of Mechanical Engineers
Date: 2002
DOI: 10.1299/JSMEC.45.258
Publisher: Springer Singapore
Date: 15-05-2019
Publisher: Elsevier BV
Date: 09-2016
Publisher: Wiley
Date: 17-08-2004
DOI: 10.1002/FLD.759
Publisher: Springer Science and Business Media LLC
Date: 10-2002
Publisher: Elsevier BV
Date: 07-2012
Publisher: Hindawi Limited
Date: 2016
DOI: 10.1155/2016/3181654
Abstract: The flow characteristics in the realistic human upper airway (HUA) with obstruction that resulted from pharyngeal collapse were numerically investigated. The 3D anatomically accurate HUA model was reconstructed from CT-scan images of a Chinese male patient (38 years, BMI 25.7). The computational fluid dynamics (CFD) with the large eddy simulation (LES) method was applied to simulate the airflow dynamics within the HUA model in both inspiration and expiration processes. The laser Doppler anemometry (LDA) technique was simultaneously adopted to measure the airflow fields in the HUA model for the purpose of testifying the reliability of LES approach. In the simulations, the representative respiration intensities of 16.8 L/min (slight breathing), 30 L/min (moderate breathing), and 60 L/min (severe breathing) were conducted under continuous inspiration and expiration conditions. The airflow velocity field and static pressure field were obtained and discussed in detail. The results indicated the airflow experiences unsteady transitional/turbulent flow in the HUA model under low Reynolds number. The airflow fields cause occurrence of forceful injection phenomenon due to the narrowing of pharynx caused by the respiratory illness in inspiration and expiration. There also exist strong flow separation and back flow inside obstructed HUA owing to the vigorous jet flow effect in the pharynx. The present results would provide theoretical guidance for the treatment of obstructive respiratory disease.
Publisher: Elsevier BV
Date: 09-2006
Publisher: IOP Publishing
Date: 05-2008
Publisher: ASMEDC
Date: 2006
DOI: 10.1115/PVP2006-ICPVT-11-93894
Abstract: Three dimensional flow over two side-by-side cantilevered cylinders is numerically studied for understanding the complex wake interference behind the cylinder pair. The two cylinders stand on the ground. The lattice Boltzmann method with multiple relaxation time is used for the solution of three dimensional unsteady flow. The simulations are carried out with Reynolds number Re = 200, aspect ratio L/D = 10 and four transverse pitch ratios: T/D = 1.2, 1.5, 2.0 and 3.0, where Re is defined by incoming velocity U, cylinder diameter D and kinetic viscosity v, L is cylinder span length and T is center to center spacing between the cylinder pair. Numerical results show that the wake patterns depend on not only T/D, but also the end flow conditions. Both the wake street and statistics of fluid force vary along the cylinder span considerably, indicating strong three dimensionality of the wake flows and their interaction.
Publisher: Elsevier BV
Date: 02-2010
Publisher: IOP Publishing
Date: 25-06-2015
Publisher: Springer Berlin Heidelberg
Date: 13-11-2013
Publisher: IOP Publishing
Date: 23-09-2005
Publisher: AIP Publishing
Date: 03-2023
DOI: 10.1063/5.0140701
Abstract: This study systematically investigates the interaction between an oscillating flow and primary cilia using numerical simulations. The primary cilia are modeled as elastic filaments with rotatable basal ends to mimic real ciliary deflections. How some governing parameters [i.e., the peak Reynolds number (Repeak), Womersley number (Wo), cilium length (L*), and streamwise spacing interval (Ld*)] regulate fluid–cilia interaction is explored. Our results indicate that within a certain range, both the span of deflection (SD) and the maximal curvature increase with the increase in Repeak, L*, and Ld*, while they decrease as the Wo increases. Compared with other parameters, Ld* affects ciliary deflection less significantly and its impact becomes nearly negligible when the cilia are separated over twice their length. Three typical stretch states are captured. For primary cilia with a short or medium length, an increase in the SD is accompanied by a greater propagation distance of the location of the maximal tensile stress (LMTS). However, this is not the case for long cilia that protrude into 1/3 of the lumen, as the arising third stretch state may greatly suppress the LMTS propagation. Our study further confirms the role of primary cilia in decreasing the wall shear stress (WSS) and altering its oscillating feature. The WSS decrease is more significant for cilia undergoing a larger SD and/or when Ld* is reduced. For a constant Ld*, a larger SD corresponds to a more uneven oscillatory shear index distribution, and the affected (i.e., less oscillatory) region appears to greatly depend on Ld*.
Publisher: Unpublished
Date: 2017
Publisher: Elsevier BV
Date: 05-2021
Publisher: IOP Publishing
Date: 12-2004
Publisher: American Chemical Society (ACS)
Date: 02-08-2017
Publisher: Elsevier BV
Date: 2006
DOI: 10.1016/J.JBIOMECH.2005.10.009
Abstract: Chronic obstructive pulmonary disease (COPD) is one of the most common diseases in human community. The COPD always results in inflammation that leads to narrowing and obstruction of the airways. The obstructive airways have significant effect on respiratory flow. In order to understand the flow phenomenon in such obstructive airways, four three-dimensional four-generation lung models based on the 23-generation model of Weibel [1963. Morphometry of the Human Lung. Springer, Academic Press, Berlin, New York] are generated. The fully three-dimensional incompressible laminar Navier-Stokes equations are solved using computational fluid dynamics (CFD) solver on unstructured tetrahedral meshes. Therein, a symmetric four-generation airway model is served as the reference, the other three models are considered to be obstructed at each generation, respectively. The calculation results show that the obstructive airway has significant influence on the air flow in both up- and down-stream airways and it even results in flow separation in the conjunction region. The re-circulation cell blocks the air from entering the downstream branches. This may be the reason why COPD patients should breathe gently, and this also provides some valuable information for medicine powder deposition.
Publisher: Informa UK Limited
Date: 07-2006
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.JBIOMECH.2012.05.050
Abstract: Obstructed sleep apnea (OSA) is a common disorder which may need surgery to widen the airway however the success rate of surgery is limited. Here we report a finding that could be used to predict the outcome of the OSA surgery. We found that inspiratory flow oscillates due to flow separation near the larynx, and the resulting periodic signal (3-5Hz) is an intrinsic property of breathing. This flow oscillating signal may be the afferent stimulus to trigger respiratory events. It is found that the flow oscillation is attenuated for the OSA subjects. The computational fluid dynamics (CFD) simulation reveals that there exists flow separation near larynx and this separation is severely weakened in the OSA upper airway model. It is believed that the flow oscillating signal can serve as the measure to quantify the breathing quality of an OSA subject. This makes it possible to predict the surgery outcome of the OSA subject by applying CFD simulation.
Publisher: Wiley
Date: 24-11-2009
DOI: 10.1002/CNM.1198
Publisher: Springer Singapore
Date: 15-05-2019
No related grants have been discovered for Yang Liu.