Numerical Simulation Of Thrombus Formation On The Wall By High Shear Rate On Orifice Flow

Recently artificial organs, especially blood pumps and stents, have been widely developed in the worldwide. However, damage of blood cells in artificial organs is an important issue in the development. The damage mainly includes thrombus and hemolysis. Thrombus and hemolysis can be caused by both physical and chemical factors. One important factor is the unreasonable flow pattern. This requires good design of artificial organs. So it is important to research on thrombus and hemolysis by studying the blood flow.As for thrombus, the modified k-ε turbulent model is used for the simulation of flow field in Orifice. In programing, finite difference method is used. Based on the flow field, transport of species with consideration of chemical reactions is simulated for thrombus formation. In this way, time history of species transportation can be obtained and the effect of model parameters on computation results is also analyzed. Wall flux model is used for the simulation of the effect of artificial wall on the change of concentrations of blood species in the fluid. Finally, the effect of Orifice configuration on platelet deposition onto the wall is also analyzed. One the other hand, dissipative particle dynamics is used for the simulation of collision and aggregation phenomena in blood flows. The results show that streamlines on Orifice flow get contracted around the Orifice part, and shear rate around the Orifice part is high, different Orifices have different flow field; thrombus model is sensitive to the parameters; conversion of blood species is found when the chemical reaction continues; at the same time, more and more activated platelet adheres onto the wall, the initial gradient of adhere number is considered to be the deposition rate; high averaged shear rate induces high deposition rate, it means that shear rate should be decreased on the medical fluid devices to reduce thrombus risk; distribution of blood species is more uniform when using turbulent diffusivity. It is also found from the results by dissipative particle dynamics that collision and aggregation of platelets happen when blood flows at the same time, and different Orifice configurations has different process of collision and aggregation. Higher averaged shear rate responds to higher platelet aggregation onto the wall.As for hemolysis evaluation, commercial package-ANSYS is used for the simulation of flow field in blood pumps. And factors which affect hemolysis evaluation are also analyzed. It is found that under the same rotating speed, head of blood pump decreases when flow rate increases; under the same flow rate, head of blood pump increases when rotating speed increases; vortex happens inside the pump in all simulation cases; wall shear rate is high when rotating speed and flow rate increase; hemolysis evaluation is high when rotating speed and flow rate increase.The paper mainly concentrates on the issues of thrombus and hemolysis in the development of artificial organs by numerical simulation. The research in this thesis provides some reference in similar research.