Mesh Sensitivity Analysis for Quantitative Shear Stress Assessment in Blood Pumps Using Computational Fluid Dynamics
Mesh Sensitivity Analysis for Quantitative Shear Stress Assessment in Blood Pumps Using Computational Fluid Dynamics
复制标题
DOI：
10.1115/1.4042043
复制
发表时间：
2019-02-01
影响因子：
1.7
通讯作者：
Kaufmann, Tim A. S.
中科院分区：
文献类型：
--
作者：
Gross-Hardt, Sascha;Boehning, Fiete;Kaufmann, Tim A. S.
减少过多的，非生理性的剪切应力导致血液创伤可能是克服血液再循环装置中许多相关并发症的关键。在这方面，计算流体动力学（CFD）对于液压和血液相容性评估的重要性越来越大。尽管如此，直接溶血评估与CFD仍然不准确，并限于定性比较，而不是定量预测。一个被低估的改善血液损伤预测精度的数量是近壁网格分辨率对复杂流动区域剪切应力定量的影响。本研究调查了必要的网格细化，以量化旋转离心血泵内两个选定的网格敏感热点（叶片前缘和尖端间隙）的剪切应力。在这些区域中的剪切应力升高，由于存在的驻点和流动周围的尖锐的边缘。无量纲网格特征数y（+）在湍流建模中是已知的，在推荐值为1时，平均低估了60%的最大壁面剪应力，但发现其精确值低于0.1。为了评价数值溶血预测的网格化相关误差，使用3 x 10（6）至30 x 10（6）元素的网格尺寸对通用离心泵进行了三维模拟。使用欧拉标量转运模型计算相应的溶血。发现网格不敏感性低于最大y（+）0.2，需要18 x 10（6）个网格单元。一个啮合相关的误差高达25%，发现为粗网格。进一步的研究需要解决：（1）可转移到其他几何形状和（2）对血液损伤估计模型的潜在适应性，以实现更好的定量预测。
The reduction of excessive, nonphysiologic shear stresses leading to blood trauma can be the key to overcome many of the associated complications in blood recirculating devices. In that regard, computational fluid dynamics (CFD) are gaining in importance for the hydraulic and hemocompatibility assessment. Still, direct hemolysis assessments with CFD remain inaccurate and limited to qualitative comparisons rather than quantitative predictions. An underestimated quantity for improved blood damage prediction accuracy is the influence of near-wall mesh resolution on shear stress quantification in regions of complex flows. This study investigated the necessary mesh refinement to quantify shear stress for two selected, meshing sensitive hotspots within a rotary centrifugal blood pump (the blade leading edge and tip clearance gap). The shear stress in these regions is elevated due to presence of stagnation points and the flow around a sharp edge. The nondimensional mesh characteristic number y(+), which is known in the context of turbulence modeling, underestimated the maximum wall shear stress by 60% on average with the recommended value of 1, but was found to be exact below 0.1. To evaluate the meshing related error on the numerical hemolysis prediction, three-dimensional simulations of a generic centrifugal pump were performed with mesh sizes from 3 x 10(6) to 30 x 10(6) elements. The respective hemolysis was calculated using an Eulerian scalar transport model. Mesh insensitivity was found below a maximum y(+) of 0.2 necessitating 18 x 10(6) mesh elements. A meshing related error of up to 25% was found for the coarser meshes. Further investigations need to address: (1) the transferability to other geometries and (2) potential adaptions on blood damage estimation models to allow better quantitative predictions.