Faculty of Mechanical Engineering and Marine Technology, Institute of Turbomachinery, University of Rostock, Rostock, Germany.
Int J Numer Method Biomed Eng. 2021 Mar;37(3):e3431. doi: 10.1002/cnm.3431. Epub 2021 Jan 31.
Numerical flow simulations that analyze the turbulent flow characteristics within a turbopump are important for optimizing the efficiency of such machines. In the case of ventricular assist devices (VADs), turbulent flow characteristics must be also examined in order to improve hemocompatibility. Turbulence increases the shear stresses in the VAD flow, which can lead to an increased damage to the transported blood components. Therefore, an understanding of the turbulent flow patterns and their significance for the numerical blood damage prediction is particularly important for flow optimizations in VADs in order to identify and thus minimize flow regions where blood could be damaged due to high turbulent stresses. Nevertheless, the turbulence occurring in VADs and the local turbulent structures that lead to increased turbulent stresses have not yet been analyzed in detail in these machines. Therefore, this study aims to investigate the turbulence in an axial VAD in a comprehensive and double tracked way. First, the flow in an axial VAD was computed using the large-eddy simulation method, and it was verified that the majority of the turbulence was directly resolved by the simulation. Then, the turbulent flow state of the VAD was quantified globally. For this purpose, a self-designed evaluation method, the power loss analysis, was used. Subsequently, local flow regions and flow structures were identified where significant turbulent stresses prevail. It will be shown that the identified regions are universal and will also occur in other axial blood pumps as well, for example, in the HeartMate II.
数值流动模拟分析涡轮泵内的湍流特性对于优化此类机器的效率非常重要。在心室辅助装置（VAD）的情况下，为了提高血液相容性，也必须检查湍流特性。湍流会增加 VAD 流中的剪切应力，从而导致输送的血液成分增加损伤。因此，了解湍流流动模式及其对数值血液损伤预测的意义对于 VAD 中的流动优化尤为重要，以便识别并因此最小化由于高湍流应力而可能导致血液受损的流动区域。然而，在这些机器中，VAD 中的湍流和导致湍流应力增加的局部湍流结构尚未得到详细分析。因此，本研究旨在以全面和双跟踪的方式研究轴向 VAD 中的湍流。首先，使用大涡模拟方法计算了轴向 VAD 中的流动，并验证了模拟直接解析了大部分湍流。然后，全局量化了 VAD 的湍流流动状态。为此，使用了自行设计的评估方法，即功率损耗分析。随后，确定了存在显著湍流应力的局部流动区域和流动结构。结果表明，所确定的区域是普遍存在的，也会出现在其他轴向血液泵中，例如 HeartMate II。
