Basic Research Of Red Blood Cell Flow In Microcirculation

The movement of the red blood cell (RBC) in blood circulation, especially in microcirculation, has been one of the most important issues that attract wide attention. As the basic structure and function unit of the human circulatory system, microcirculation plays an important role in the whole blood circulation. So far, however, the studies on the flow characteristics of the blood and its impact on the vascular wall in microvascular are very limited.In this thesis, the state-of-art of the development of microcirculation fluid mechanics is given. The current approaches used to analyze the movement of microcirculation are analyzed and compared. After establishing the basic model and the flow equation of blood circulation, and analysing the deformability of red blood cells, we propose a model which is very suitable for microcirculation. In specific, the continuity equation and momentum equation are determined. The Lattice Boltzmann method (LBM) combined with the immersed boundary method (IBM) to simulate the RBC movement in microcirculation is presented. The LBM is used to simulate the incompressible flow field, and the IBM is utilized to incorporate the solid-fluid interaction. The combination keeps the advantages of the LBM in simulating different kinds of flows, and provides a better approach to solve the solid-fluid boundary conditions.In literature, the shape of the RBC is generally regarded as rigid or oval ball. In this thesis, however, the RBC is considered as biconcave liquid capsules, while the membrane is represented by a set of points that move with the fluid points, and external forces are induced on the fluid by adding a force term to the lattice Boltzmann equation. The blunt velocity profiles of the RBC flows are obtained, and the motion of the cell performs tumbling-rotating or tank-treading in the vessel. A circle of the deformation and movement of one single RBC is simulated. In order to simulate the movement of the RBC moving along the axis of the blood flow, both the two-dimensional model and the three-dimensional model are established. Results obtained are in excellent agreement with the existing medical experiments, which shows the effectiveness of the proposed methods.