Pulsatile flow fields in rigid abdominal aortic aneurysm （AAA） models were investigated numerically, and the simulation results are found in good agreement with particle image velocimetry （PIV） measurements. There are one or more vortexes in the AAA bulge, and a fairly high wall shear stress exists at the distal end, and thus the AAA is in danger of rupture. Medical treatment consists of inserting a vascular stent-graft in the AAA, which would decrease the blood impact to the inner walls and reduce wall shear stress so that the rupture could be prevented. A new computational model, based on porous medium model, was developed and results are documented. Therapeutic effect of the stent-graft was verified numerically with the new model.
The passage of red blood cells （RBCs） through capillaries is essential for human blood microcirculation. This study used a moving mesh technology that incorporated leader-follower pairs to simulate the fluid-structure and structure-structure interac- tions between the RBC and a microvessel stenosis. The numerical model consisted of plasma, cytoplasm, the erythrocyte membrane, and the microvessel stenosis. Computational results showed that the rheology of the RBC is affected by the Reynolds number of the plasma flow as well as the surface-to-volume ratio of the erythroeyte. At a constant inlet flow rate, an increased plasma viscosity will improve the transit of the RBC through the microvessel stenosis. For the above reasons, we consider that the decreased hemorheology in microvessels in a pathological state may primarily be attributed to an increase in the number of white blood cells. This leads to the aggregation of RBCs and a change in the blood flow structure. The present fundamental study of hemorheology aimed at providing theoretical guidelines for clinical hemorheology.
The effect of disturbed flow on the mass trans- fer from arterial surface to flowing blood was studied nu- merically, and the results were compared with that of our previous work. The arterial wall was assumed to be vis- coelastic and the blood was assumed to be incompressible and non-Newtonian fluid, which is more close to human arte- rial system. Numerical results indicated that the mass trans- fer from the arterial surface to flowing blood in regions of disturbed flow is positively related with the wall shear rates and it is significantly enhanced in regions of disturbed flow with a local minimum around the reattachment point which is higher than the average value of the downstream. There- fore, it may be implied that the accumulation of cholesterol or lipids within atheromatous plaques is not caused by the reduced efflux of cholesterol or lipids, but by the infiltration of the LDL （low-density lipoprotein） from the flowing blood to the arterial wall.
