Simulation of blood flow using kinetic theory based multiphase model.

摘要

Blood is a mixture of red blood cells (RBCs) or erythrocytes, platelets or thrombocytes, and white blood cells (WBCs) or leukocytes suspended in plasma. Until very recently, however, blood flow was modeled as a single phase fluid. The objective of this thesis research is the hemodynamic study of blood flow using kinetic theory based multiphase computational fluid dynamics (CFD).;Two-phase kinetic theory CFD models were used to simulate the blood flow of plasma and RBCs in both a straight capillary tube and a realistic model of a right coronary artery (RCA). This model explains the Fahraeus-Linqvist effect: the migration of red blood cells from the wall toward the center due to shear induced diffusion, and the blood viscosity dependence on vessel diameter and hematocrit. The computed hematocrit distribution using a complete two phase CFD model and a fully developed flow approximation solution in the narrow tube agrees with experimental measurements. The momentum and granular temperature boundary layers are predicted. A pulsatile inlet velocity is used to model the realistic model of an RCA. The red blood cell volume fractions, shear stresses, shear stress gradients, granular temperatures, viscosities, and phase velocities varied with time and position during each cardiac cycle. The wall shear stress and wall shear stress gradients (both spatial and temporal) were found to be highest on the inside area of maximum curvature. Potential atherosclerosis sites are identified using these computational results.;Simplified equations describing for multiphase kinetic theory model are used to simulate the blood flow of platelets, red blood cells, and plasma. A fully developed parabolic velocity distribution is assumed. The near wall buildup of platelets and its dependence on the hematocrit and wall shear rate in the vessel are explained as their interactions with dense red blood cells.;The simplified equations of multiphase kinetic theory model are modified by including the electrostatic effect caused by the negative surface charged lipoprotein nano-particles. The structure of the charge distribution in the computation domain is modeled with the electric potential obtained from the Poisson equation. The migration of lipoproteins away from the center of vessel is shown to be a result of electric forces. The appearance of high density lipoprotein (HDL) produces higher electric potential and transports low density lipoproteins away from the center. There is a higher ratio of HDL to low density lipoprotein (LDL) near the wall. The implication is that when the ratio of HDL to LDL concentrations is optimum in the human body this may inhibit the formation of atherosclerosis by increasing the biochemical reaction of HDL on the artery wall to decrease the oxidization of LDL.