Schüle Chan Yong, Thamsen Bente, Blümel Bastian, Lommel Michael, Karakaya Tamer, Paschereit Christian Oliver, Affeld Klaus, Kertzscher Ulrich
Biofluid Mechanics Laboratory, Charité-Universitätsmedizin Berlin.
Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Berlin, Germany.
Artif Organs. 2016 Nov;40(11):E192-E202. doi: 10.1111/aor.12725. Epub 2016 Apr 18.
Left ventricular assist devices (LVADs) have become a standard therapy for patients with severe heart failure. As low blood trauma in LVADs is important for a good clinical outcome, the assessment of the fluid loads inside the pump is critical. More specifically, the flow features on the surfaces where the interaction between blood and artificial material happens is of great importance. Therefore, experimental data for the near-wall flows in an axial rotary blood pump were collected and directly compared to computational fluid dynamic results. For this, the flow fields based on unsteady Reynolds-averaged Navier-Stokes simulations-computational fluid dynamics (URANS-CFD) of an axial rotary blood pump were calculated and compared with experimental flow data at one typical state of operation in an enlarged model of the pump. The focus was set on the assessment of wall shear stresses (WSS) at the housing wall and rotor gap region by means of the wall-particle image velocimetry technique, and the visualization of near-wall flow structures on the inner pump surfaces by a paint erosion method. Additionally, maximum WSS and tip leakage volume flows were measured for 13 different states of operation. Good agreement between CFD and experimental data was found, which includes the location, magnitude, and direction of the maximum and minimum WSS and the presence of recirculation zones on the pump stators. The maximum WSS increased linearly with pressure head. They occurred at the upstream third of the impeller blades and exceeded the critical values with respect to hemolysis. Regions of very high shear stresses and recirculation zones could be identified and were in good agreement with simulations. URANS-CFD, which is often used for pump performance and blood damage prediction, seems to be, therefore, a valid tool for the assessment of flow fields in axial rotary blood pumps. The magnitude of maximum WSS could be confirmed and were in the order of several hundred Pascal.
左心室辅助装置（LVADs）已成为重度心力衰竭患者的标准治疗方法。由于LVADs中的低血液创伤对于良好的临床结果很重要，因此评估泵内的流体负荷至关重要。更具体地说，血液与人工材料相互作用表面上的流动特性非常重要。因此，收集了轴向旋转血泵近壁流动的实验数据，并直接与计算流体动力学结果进行比较。为此，计算了基于轴向旋转血泵的非定常雷诺平均纳维-斯托克斯模拟-计算流体动力学（URANS-CFD）的流场，并与泵放大模型中一个典型运行状态下的实验流动数据进行了比较。重点是通过壁面粒子图像测速技术评估壳体壁和转子间隙区域的壁面剪应力（WSS），以及通过油漆侵蚀法可视化泵内表面的近壁流动结构。此外，还测量了13种不同运行状态下的最大WSS和叶尖泄漏体积流量。发现CFD与实验数据之间具有良好的一致性，包括最大和最小WSS的位置、大小和方向以及泵定子上再循环区域的存在。最大WSS随压头线性增加。它们出现在叶轮叶片的上游三分之一处，并且超过了与溶血相关的临界值。可以识别出高剪切应力区域和再循环区域，并且与模拟结果吻合良好。因此，常用于泵性能和血液损伤预测的URANS-CFD似乎是评估轴向旋转血泵流场的有效工具。最大WSS的大小可以得到证实，其量级为几百帕斯卡。
