Department of Management and Engineering, Linköping University, SE-581 83 Linköping, Sweden.
Med Eng Phys. 2012 Oct;34(8):1139-48. doi: 10.1016/j.medengphy.2011.12.002. Epub 2011 Dec 29.
In this study, large-eddy simulation (LES) is employed to calculate the disturbed flow field and the wall shear stress (WSS) in a subject specific human aorta. Velocity and geometry measurements using magnetic resonance imaging (MRI) are taken as input to the model to provide accurate boundary conditions and to assure the physiological relevance. In total, 50 consecutive cardiac cycles were simulated from which a phase average was computed to get a statistically reliable result. A decomposition similar to Reynolds decomposition is introduced, where the WSS signal is divided into a pulsating part (due to the mass flow rate) and a fluctuating part (originating from the disturbed flow). Oscillatory shear index (OSI) is plotted against time-averaged WSS in a novel way, and locations on the aortic wall where elevated values existed could easily be found. In general, high and oscillating WSS values were found in the vicinity of the branches in the aortic arch, while low and oscillating WSS were present in the inner curvature of the descending aorta. The decomposition of WSS into a pulsating and a fluctuating part increases the understanding of how WSS affects the aortic wall, which enables both qualitative and quantitative comparisons.
在这项研究中，采用大涡模拟（LES）来计算特定于人体主动脉的受扰流场和壁面切应力（WSS）。使用磁共振成像（MRI）进行速度和几何测量，作为模型的输入，以提供准确的边界条件并确保生理相关性。总共模拟了 50 个连续的心动周期，从中计算出一个相位平均值，以获得统计上可靠的结果。引入了类似于雷诺分解的分解，其中 WSS 信号被分为脉动部分（由于质量流量）和脉动部分（源自受扰流）。以新颖的方式将振荡剪切指数（OSI）绘制为时间平均 WSS，并且可以轻松找到壁上存在升高值的位置。一般来说，在主动脉弓的分支附近发现了高且振荡的 WSS 值，而在降主动脉的内弯曲处存在低且振荡的 WSS 值。将 WSS 分解为脉动和脉动部分增加了对 WSS 如何影响主动脉壁的理解，这使得定性和定量比较成为可能。
