Torner Benjamin, Konnigk Lucas, Wurm Frank-Hendrik
Institute of Turbomachinery, University of Rostock, Rostock, Germany.
Int J Artif Organs. 2019 Dec;42(12):735-747. doi: 10.1177/0391398819861395. Epub 2019 Jul 21.
The blood damage prediction in rotary blood pumps is an important procedure to evaluate the hemocompatibility of such systems. Blood damage is caused by shear stresses to the blood cells and their exposure times. The total impact of an equivalent shear stress can only be taken into account when turbulent stresses are included in the blood damage prediction. The aim of this article was to analyze the influence of the turbulent stresses on the damage prediction in a rotary blood pump's flow. Therefore, the flow in a research blood pump was computed using large eddy simulations. A highly turbulence-resolving setup was used in order to directly resolve most of the computed stresses. The simulations were performed at the design point and an operation point with lower flow rate. Blood damage was predicted using three damage models (volumetric analysis of exceeded stress thresholds, hemolysis transport equation, and hemolysis approximation via volume integral) and two shear stress definitions (with and without turbulent stresses). For both simulations, turbulent stresses are the dominant stresses away from the walls. Here, they act in a range between 9 and 50 Pa. Nonetheless, the mean stresses in the proximity of the walls reach levels, which are one order of magnitude higher. Due to this, the turbulent stresses have a small impact on the results of the hemolysis prediction. Yet, turbulent stresses should be included in the damage prediction, since they belong to the total equivalent stress definition and could impact the damage on proteins or platelets.
旋转血泵中的血液损伤预测是评估此类系统血液相容性的重要步骤。血液损伤是由作用于血细胞的剪切应力及其暴露时间引起的。只有在血液损伤预测中纳入湍流应力时，才能考虑等效剪切应力的总影响。本文的目的是分析湍流应力对旋转血泵血流中损伤预测的影响。因此，使用大涡模拟计算了研究用血泵中的血流。为了直接解析大部分计算应力，采用了高分辨率湍流设置。模拟在设计点和较低流速的运行点进行。使用三种损伤模型（超过应力阈值的体积分析、溶血传输方程以及通过体积积分的溶血近似）和两种剪切应力定义（包含和不包含湍流应力）来预测血液损伤。对于这两种模拟，远离壁面时湍流应力是主导应力。在此，它们的作用范围在9至50帕之间。尽管如此，壁面附近的平均应力达到了高一个数量级的水平。因此，湍流应力对溶血预测结果的影响较小。然而，湍流应力应包含在损伤预测中，因为它们属于总等效应力定义，并且可能影响对蛋白质或血小板的损伤。
