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Neurological diseases such as cancer, damage blood brain barrier and consequently cause more permeability in tissues. In general if there is damage to the brain tissues, the contrast agent used in MRI, diffuses outside the capillaries and the MRI picture brightness changes. The purpose of this paper is to show the effects of different parameters on the contrast agent diffusion in the brain capillary. In this study, the lattice Boltzmann method with multi-relaxation time (MRT) is used to simulate the flow in the capillary and porous media around it. The results show that the porosity in extravascular tissues (it shows the tissue damage), the kind of contrast agent and capillaries curvature have impact on the contrast agent diffusion in the tissues. The presented results show the effects of curvature on shear stress and thus on mass transfer in the capillary. It should be noted that the presented results have been evaluated by previous statistical and analytical results for flow in the damaged brain capillary with different permeability. It has been shown that the lattice Boltzmann method is able to simulate the complex problems especially in porous media.

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The purpose of this paper is to investigate theLow-Density Lipoproteins (LDL) mass transfer in vessel walls using the Lattice Boltzmann Method (LBM). High Schmidt number of LDL leads to numerical instability of LBM.In order to solve this problem, LBM and finite volume method (FVM) are combined.In this hybrid method, the blood velocity field is solved by LBM using the single relaxation time, SRT, model and FVM has been used for LDL concentration equation. LBM is able to simulate flow and mass transfer for the Schmidt number, Sc, up to 3000 only if the time consuming multi relaxation time is used. However, the purposed hybrid method suggested in this article can be used to solve the problem for Sc as high as 107. Good agreement between our results obtained from the hybrid simulation and the available results in the literature and noticeable decrease in CPU time compared with when the LBM is used for both flow and mass transfer, indicates the ability of the hybrid method.Finally, the hybrid methodis used to simulate the mass transfer of LDL particles and investigate the effective factors for increasing the surface concentration, such as the size of LDL particles, wall suction velocity, wall shear stress, Newtonian and non-Newtonian fluids behavior and change of concentration boundary layer with various Schmidt number.

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The variation of wall shear stress (WSS) in the microvessels may damage the endothelial layers. It also changes the mass diffusion and sediment and may be considered as an important factor in the formation of the fatty plaques and causing heart disease. According to the importance of the issue, the aim of this paper is to study the effective parameters on the wall shear stress in microvessels. In this paper, the hybrid method, combined lattice Boltzmann and immersed boundary methods is used to simulate the red blood cell (RBC) motion in the plasma flow. It should be mentioned that red blood cell has significant effect on WSS, in this regard; the present results show that the blood rheological behavior has the important effect on WSS. The results also demonstrate the effect of stenosis severity and RBC location in different regions on wall shear stress and consequently causing heart, coronary disease. It should be noted that the presented results have been evaluated by previous numerical results for microvessels and the results show the ability of lattice Boltzmann method to simulate complex problems especially for modeling the deformable solid objects suspended in the fluid.