Computational Modeling of Mechanical Heart Valves

描述（由申请人提供）：目前机械人工心脏瓣膜（MPHV）的设计远非理想，并且在植入后经常出现严重并发症，如溶血、血小板破坏和血栓栓塞。这些病理状况被认为是由于血液元素暴露于机械假体附近的复杂湍流场引起的过度血液动力学应力而引起的。因此，改进和进一步完善现有MPHV设计的一个关键先决条件是深入了解它们引起的流场。本文提出了一项为期5年的研究计划，旨在开发和验证一种最先进的数值模拟工具，用于定量准确地预测人工瓣膜中发生的所有流动现象。提出的研究计划的具体目标是：1）开发一种高精度和高效率的数值方法，用于模拟真实双叶MPHV几何形状中的非定常三维流动：2）开发和实现MPHV流动模拟中的先进湍流闭合模型，该模型能够准确预测生理雷诺数下脉动流向湍流的转变和再层化; 3）进行详细的实验室实验，以获得全面的数据集，并使用这些数据集来验证和微调CFD模型;以及4）应用CFD方法详细研究双叶MPHV设计中的湍流结构，并探索其对临床观察到的并发症的影响。提出的CFD方法将彻底改变目前的阀门设计和测试实践。该方法将能够产生的详细程度的阀门流场的描述，目前无法单独通过实验，导致大量的时间和成本节省在研究和开发阶段。这项工作还将导致一个计算框架，用于评估植入给定MPHV设计可能导致血栓栓塞并发症的可能性。

DESCRIPTION (provided by applicant): Present-day designs of mechanical prosthetic heart valves (MPHV) are far from ideal and significant complications such as hemolysis, platelet destruction, and thromboembolism-often arise after their implantation. These pathological conditions are believed to be caused by the exposure of blood elements to excessive hemodynamic stresses induced by the complex, turbulent flow field in the vicinity of the mechanical prosthesis. Therefore, a critical prerequisite for improving and further refining existing MPHV designs is the in-depth understanding of the flow fields they induce. A 5-year research plan is proposed herein aimed at developing and validating a state-of-the art numerical simulation tool for obtaining quantitatively accurate predictions of all flow phenomena occurring in prosthetic valves. The specific aims for the proposed research program are: 1) To develop a highly accurate and efficient numerical method for simulating unsteady, three-dimensional flows in realistic bileaflet MPHV geometries; 2) To develop and implement in MPHV flow simulations advanced turbulence closure models capable of accurate predictions of transition to turbulence and relaminarization in pulsatile flows at physiological Reynolds numbers; 3) To conduct detailed laboratory experiments to obtain comprehensive data sets and use these data sets to validate and fine-tune the CFD model; and 4) To apply the CFD method to study in detail the structure of turbulence in bi-leaflet MPHV designs and explore its implications to clinically observed complications. The proposed CFD method will revolutionize current valve design and testing practices. The method will be capable of yielding descriptions of the valve flow fields at a level of detail not currently accessible by experiments alone, leading to substantial time and cost savings during the research and development phase. This work will also lead to a computational framework for assessing the likelihood that implantation of a given MPHV design may lead to thromboembolic complications.