Investigation of the near-wall flow physics of blood in narrow gaps at technically relevant Reynolds numbers

在技​​术相关的雷诺数下研究狭窄间隙中血液的近壁流动物理学

• 批准号: 469384587
• 负责人: Professorin Dr.-Ing. Jeanette Hussong
• 金额: --
• 依托单位: Lehrstuhl Strömungsmaschinen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/469384587?language=en
• 关键词: Investigation; near; wall; flow; physics

Ventricular assist devices (VADs) are implanted in people with severe heart failure to maintain the blood circulation. The most commonly implanted VADs are turbopumps. A major aim of a VAD optimization is to minimize flow-induced blood damage that occurs due to non-physiologically high stresses. This blood damage is often computed using flow simulations and empirical blood damage models. However, it is currently not possible to calculate quantitatively correct damage values in VAD simulations, e.g., for hemolysis (damage to erythrocytes).A possible reason for the miscalculation of hemolysis could be found in the treatment of blood in the VAD simulation as single-phase fluid. However, multiphase flow effects could occur. For example, erythrocyte migration could happen in the blood flow in narrow VAD gaps, where the highest stresses act, with erythrocytes migrating to the center of the gap and a cell-free plasma layer (CFL) forming near the walls. This CFL will affect the acting stresses and hemolysis in the VAD gaps. However, the CFL has not yet been investigated experimentally in VAD gaps, nor has it been considered in VAD simulations.Therefore, the main objectives of the project are the experimental flow field investigation in blood-flowing, narrow gaps; the characterization of the CFL in the gap; as well as the numerical modeling of the gap flow.Since an accessibility for measurements in a VAD gap is limited, the geometric parameters and flow conditions of the gaps are mimicked in microchannels, through which animal blood flows. On the one hand, optical flow investigations will be carried out using micro-particle image velocimetry (μ-PIV) and astigmatism particle tracking velocimetry (APTV), in order to describe the blood flow and to characterize the CFL. On the other side, wall shear stress measurements will be performed in the microchannels by using direct wall shear stress sensors. For this purpose, single-phase blood analogues fluids (BEF) will be also used. By comparing the wall shear stresses between BEF and animal blood, the difference in the acting stresses due to the plasma layer in the animal blood can be quantified.Subsequently, the blood flow in the microchannels will be numerically modeled by means of flow simulations with an extended fluid model, which takes the plasma layer into account. After that, a validation of the model and a comparison with current fluid models will be performed. In the last project objective, the influence of different inlet geometries on the plasma layer formation in the gap will be also investigated and recommendations for the design of the inlet area will be derived.The achievement of the project goals forms the basis for an improved understanding of blood flow in the narrow gaps of VADs and their correct numerical modelling. Based on this, blood damage in VADs can be calculated in an improved way in the future.

心室辅助装置（VAD）植入严重心力衰竭患者体内，以维持血液循环。最常植入的VAD是涡轮泵。VAD优化的主要目的是最小化由于非生理高应力而发生的流动诱导的血液损伤。这种血液损伤通常使用流动模拟和经验血液损伤模型来计算。然而，目前不可能在VAD模拟中定量计算正确的损伤值，例如，溶血的错误计算的可能原因可以在VAD模拟中将血液处理为单相流体中找到。然而，可能发生多相流效应。例如，红细胞迁移可能发生在狭窄的VAD间隙中的血流中，其中最高的应力作用，红细胞迁移到差距的中心，并且在壁附近形成无细胞血浆层（CFL）。这种CFL将影响VAD间隙中的作用应力和溶血。然而，CFL还没有在VAD间隙中进行实验研究，也没有在VAD模拟中考虑。因此，该项目的主要目标是在血液流动的狭窄间隙中进行实验流场研究，CFL在差距中的特性，以及差距流的数值模拟。由于在VAD间隙中测量的可及性是有限的，在动物血液流过的微通道中模拟间隙的几何参数和流动条件。一方面，光流研究将使用微粒子图像测速仪（μ-PIV）和像散粒子跟踪测速仪（APTV）进行，以描述血液流动和表征CFL。另一方面，将通过使用直接壁面剪切应力传感器在微通道中进行壁面剪切应力测量。为此，还将使用单相血液模拟液（BEF）。通过比较BEF和动物血液的壁面切应力，可以量化由于血浆层在动物血液中的作用应力的差异，随后，通过流动模拟的方式，采用扩展的流体模型，考虑血浆层的血液流动的数值模拟。在此之后，将执行模型的验证以及与当前流体模型的比较。在最后一个项目目标中，还将研究不同入口几何形状对差距中等离子体层形成的影响，并将得出入口区域设计的建议。项目目标的实现为更好地理解VAD窄间隙中的血液流动及其正确的数值模拟奠定了基础。在此基础上，可以在未来以改进的方式计算VAD中的血液损伤。