弯曲动脉的血流动力学数值分析

利用计算流体力学的理论和方法对弯曲动脉中的血流动力学进行数值分析，是研究心血管疾病流体动力学机理的一种行之有效的方法。本文将升主动脉、主动脉弓和降主动脉联系起来作为弯曲动脉几何模型，给出了血液流动的边界条件以及计算条件。根据生理脉动流条件，对狗的弯曲动脉几何模型内发展中的血液流动进行了有限元数值模拟，并利用可视化方法对血液流动的轴向速度、二次流、壁面切应力等计算结果进行了分析。研究结果表明，在弯管内侧壁处，同时存在主流方向和二次流方向的回流，此处容易形成涡流。弯管内侧壁比外侧壁的壁面切应力具有更强的脉动性。

Numerical analysis of hemodynamics in curved arteries

Numerical analysis according to the theories and methods of computational fluid dynamics (CFD) is one of the effective methods studying the hemodynamic mechanisms of cardiovascular disease in curved arteries. The ascending aorta, the aortic arch and the descending aorta are considered together as the geometric model. The boundary conditions and calculation conditions are proposed. The numerical simulation of the developing blood flow in the geometric model of dogs is carried out with finite element method (FEM) according to the physiologically pulsatile flow conditions. The initial\|boundary conditions include: non\|slip conditions on the wall, symmetric conditions in the symmetric plane, physiological pulsatile entrance velocity and outlet pressure conditions. Several pulsation periods of calculation are performed to obtain the final convergent results. The calculation results of blood flow such as the axial velocity, secondary flow, wall shear stress and pressure wave are analyzed with scientific visualization method. Their temporal\|spatial distributions are intuitively shown with a lot of 2\|d and 3\|d figures. The research results indicate there are simultaneous reversed flows in the main flow and the secondary flow directions in the inner bend where vortex is prone to occur. Reversed flows are mainly located in the downstream area and closely related to the increase and decrease of entrance velocity. With the propagation of pressure wave to the downstream along the centerline the dicotism weakens gradually and the pressure wave becomes steep gradually. The magnitude and variation range of wall shear stresses in the inner bend of the aortic arch are much larger than those in the outer bend. The endothelium cells in the inner bend are much easier to suffer from oxygen lack caused by vortex and be injured by alternative wall shear stresses. The injury of endothelium has serious relationship with the growing and developing of lipopexia and atherosclerosis.