A finite volume solver for Casson fluid flow based on SIMPLE algorithm of Newtonian fluid on unstructured collocated grid is developed to simulate haemodynamics in complex vessel. The discretization of convective flux...
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A finite volume solver for Casson fluid flow based on SIMPLE algorithm of Newtonian fluid on unstructured collocated grid is developed to simulate haemodynamics in complex vessel. The discretization of convective flux and source term are similar with Newtonian fluid. For the discretization of diffusion flux, viscosity will take the value calculated from the flow field of previous iteration so as to avoid the complexity caused by the complicated viscosity expression as a function of shear rate. Then the discretization of momentum equation is similar with that of Newtonian fluid with variable viscosity and SIMPLE algorithm can be used to resolve the pressure-velocity coupling. With this algorithm, blood flows in a T-typed bifurcation are simulated. The simulation results of Casson fluid are more consistent with experimental data than that of Newtonian fluid, which indicates that using Casson model to simulate non-Newtonian characteristics of blood flow is successful and necessary.
This paper considers an epidemic model of a vector-borne disease which has the vectormediated transmission only. The incidence term is of the bilinear mass-action form. It is shown that the global dynamics is complete...
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This paper considers an epidemic model of a vector-borne disease which has the vectormediated transmission only. The incidence term is of the bilinear mass-action form. It is shown that the global dynamics is completely determined by the basic reproduction number Ro. If Ro ≤ 1, the diseasefree equilibrium is globally stable and the disease dies out. If Ro 〉 1, a unique endemic equilibrium is globally stable in the interior of the feasible region and the disease persists at the endemic equilibrium. Numerical simulations are presented to illustrate the results.
Turbulent mixing layer flow was simulated by the discrete vortex method, and viscosity was modeled by the random walk method and the solid wall was represented by the vortex sheet in the simulation. The predictions of...
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Turbulent mixing layer flow was simulated by the discrete vortex method, and viscosity was modeled by the random walk method and the solid wall was represented by the vortex sheet in the simulation. The predictions of the profiles of mean velocity and turbulent flow parameters agree well with experimental data. The results show that the peak value of Reynolds shear stress increases but the fluctuations of the peak value occur because of vortex-pairing, and vorticity peak value increases in the downstream direction. Then the effect of Reynolds number on the distribution of the turbulent flow parameters at the same velocity ratio was explored. It seems that the peak values of Reynolds shear stress under different Reynolds numbers will increase at the similar slope in the downstream direction. The average vorticity peak value will decrease in the downstream direction, and the decrease rate will increase with Reynolds number. In addition, the vorticity peak value in each section will increase nearly linearly with Reynolds number.
The dimension of erythrocyte is close to capillary diameter and in microcirculation blood should be treated as a two-phase flow system, i.e., erythrocytes suspended in plasma. The rheological property of erythrocytes ...
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The dimension of erythrocyte is close to capillary diameter and in microcirculation blood should be treated as a two-phase flow system, i.e., erythrocytes suspended in plasma. The rheological property of erythrocytes will significantly influence the hemodynamics. In our experiment, the motion and deformation of erythrocytes in a microfluidic chip with rectangular cross-section microchannel was captured by optical microscope and high speed CCD camera. The aggregation, deformation and common movement forms of erythrocytes were observed under different viscosity, hematocrit and velocity. It was found that erythrocytes behaved a regular biconcave disc shape at low velocity and low-to-medium viscosity, and always rolled and rotated themselves in their movement. At high velocity and medium viscosity, RBCs elongated obviously along the flow direction and presented a flat oval shape together with a tank-treading motion (TTM).
multiphaseflow induced CO2 corrosion has resulted in serious losses in oil and gas production. In this paper, gas‐liquid two‐phase vertical upward slug flow has been analyzed from aspects containing flow structure,...
multiphaseflow induced CO2 corrosion has resulted in serious losses in oil and gas production. In this paper, gas‐liquid two‐phase vertical upward slug flow has been analyzed from aspects containing flow structure, hydrodynamic characteristics, mass transfer characteristics and their effects on pipe wall and corrosion product film, and it is found that slug flow has a distinct effect on transports of corroding species to and of corrosion products from the wall, momentum interchange between fluid and wall and the formation and damage of corrosion product film. In addition, the transports of corrosive species and corrosion product are also an important step in CO2 corrosion process. It is assumed that the slug flow induced CO2 corrosion of pipeline is dependent on the non‐linear coupling of the characteristics including the shear stress, the normal stress, the mass transfer coefficient, and the electrochemical reaction.
To investigate the mechanism of active control for flow separation in rectangle diffuser by vortex generator jets (VGJs) method, numerical analysis with large-eddy simulation and experimental measurement by particle i...
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The attempt of the author in this research is made to calculate a heat transfer coefficient (HTC) by combining the filmwise theory with the dropwise notion for ethanol‐water mixtures condensation. A new model, includ...
The attempt of the author in this research is made to calculate a heat transfer coefficient (HTC) by combining the filmwise theory with the dropwise notion for ethanol‐water mixtures condensation. A new model, including ethanol concentration, vapor pressure and velocity, is developed by introducing a characteristic coefficient to combine the two mentioned‐above theories. Under different concentration, pressure and velocity, the calculation is in comparison with experiment. It turns out that the calculation value is in good agreement with the experimental result; the maximal error is within ±30.1%. In addition, the model is applied to calculate related experiment in other literature and the values obtained agree well with results in reference.
ZnS‐CuInS2‐AgInS2 solid solution photocatalysts were successfully prepared by co‐precipitation method with heat treatment under different atmosphere ( N2 and H2S). XRD, XRF, UV‐vis, and SEM were used to characteri...
ZnS‐CuInS2‐AgInS2 solid solution photocatalysts were successfully prepared by co‐precipitation method with heat treatment under different atmosphere ( N2 and H2S). XRD, XRF, UV‐vis, and SEM were used to characterize the prepared photocatalysts, indicated that the composition of result photocatalysts were different from each other and also the rate of charge, though they possessed a wurtzite‐type phase structure. The photocatalysts all showed photocatalytic activities for H2 evolution from aqueous solutions containing SO32− and S2− as sacrificial reagents under visible light irradiation with Ru loading, but sample treated under H2S atmosphere performed better, the possible reason was proposed.
In partially premixed combustion of gas turbine, the combustion temperature should be lowed in order to reduce NOx. One solution is lean premixed combustion. However, the problem is that large excess air ratio may mak...
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In partially premixed combustion of gas turbine, the combustion temperature should be lowed in order to reduce NOx. One solution is lean premixed combustion. However, the problem is that large excess air ratio may make the combustion unstable. A novel combustor with circumferential reverse flow of fuel gas is proposed for settling this problem. A 10 kw furnace is established to test performance of this combustor. Three factors such as primary air ratio, position of secondary air, total excess air ratio are studied. The emission characteristics and axial flame temperature distribution are studied. Basing on experimental results, the axial flame temperature and NOr emission increase with primary air ratio and axial length of second stream, and decrease with total excess air ratio. When the total excess air ratio is larger than 1.05, the combustor presents a lower temperature field and much lower NOx emission （less than 10 ppm）.
Evaporating falling film on horizontal tubes has been widely used in desalinization, refrigeration, chemical process industries, and so on. In this paper, the flow characteristics of falling film outside horizontal tu...
Evaporating falling film on horizontal tubes has been widely used in desalinization, refrigeration, chemical process industries, and so on. In this paper, the flow characteristics of falling film outside horizontal tubes in horizontal air flows was studied theoretically and experimentally. Two low patterns of the falling film, i.e., droplet flow pattern and columnar flow pattern, were considered. Effects of the velocity of airflow, the flux of falling film flow, the external diameter of tube and the surface property of tube on the falling film flowing characters were investigated. Experimental study indicated that, in a definite flow scale, as the flow increased, the diameters of falling droplets and falling columns of the liquid enlarged, and the liquid film became thick and the area covered by the liquid film increased. As the air velocity increased, the offset of the droplet and the column to the top of the tube enlarged, and the rate of increase come down until it complete depart from the the top of the horizontal tube. Besides, a theoretical model was established about the offset of the droplet and liquid column from the top of the tube under the force of the horizontal air flows, and the model was validated by a comparison between the numerical predictions and experimental data.A further analysis about the excursion law of falling film flow outside horizontal tube was also made at the last paprt of the paper.
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