Ge Liang, Jones S Casey, Sotiropoulos Fotis, Healy Timothy M, Yoganathan Ajit P
School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0335, USA.
J Biomech Eng. 2003 Oct;125(5):709-18. doi: 10.1115/1.1614817.
A numerical method is developed for simulating unsteady, 3-D, laminar flow through a bileaflet mechanical heart valve with the leaflets fixed. The method employs a dual-time-stepping artificial-compressibility approach together with overset (Chimera) grids and is second-order accurate in space and time. Calculations are carried out for the full 3-D valve geometry under steady inflow conditions on meshes with a total number of nodes ranging from 4 x 10(5) to 1.6 x 10(6). The computed results show that downstream of the leaflets the flow is dominated by two pairs of counter-rotating vortices, which originate on either side of the central orifice in the aortic sinus and rotate such that the common flow of each pair is directed away from the aortic wall. These vortices intensify with Reynolds number, and at a Reynolds number of approximately 1200 their complex interaction leads to the onset of unsteady flow and the break of symmetry with respect to both geometric planes of symmetry. Our results show the highly 3-D structure of the flow; question the validity of computationally expedient assumptions of flow symmetry; and demonstrate the need for highly resolved, fully 3-D simulations if computational fluid dynamics is to accurately predict the flow in prosthetic mechanical heart valves.
开发了一种数值方法，用于模拟通过固定瓣叶的双叶机械心脏瓣膜的非定常三维层流。该方法采用双时间步长人工可压缩性方法以及重叠（嵌套）网格，在空间和时间上具有二阶精度。在稳定流入条件下，对具有4×10⁵至1.6×10⁶个节点总数的网格上的完整三维瓣膜几何形状进行了计算。计算结果表明，在瓣叶下游，流动由两对反向旋转的涡旋主导，这些涡旋起源于主动脉窦中央孔的两侧，并以这样的方式旋转，使得每对涡旋的共同流动方向远离主动脉壁。这些涡旋随着雷诺数的增加而增强，在雷诺数约为1200时，它们的复杂相互作用导致非定常流动的开始以及相对于两个几何对称平面的对称性破坏。我们的结果显示了流动的高度三维结构；质疑了计算上方便的流动对称性假设的有效性；并证明，如果计算流体动力学要准确预测人工机械心脏瓣膜中的流动，则需要进行高分辨率的全三维模拟。
