Computational Modeling of Mechanical Heart Valves

描述（由申请人提供）：目前机械假心瓣膜（MPHV）的设计远远不够理想，植入后经常出现溶血、血小板破坏和血栓栓塞等严重并发症。这些病理状况被认为是由于机械假体附近复杂的湍流流场引起的血液元素暴露于过度的血流动力学应力所引起的。因此，改进和进一步完善现有MPHV设计的一个关键前提是深入了解它们所诱导的流场。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，以获得对人工瓣膜中发生的所有流动现象的定量准确预测。本研究计划的具体目标是：1)开发一种高精度、高效的数值方法来模拟实际双小叶MPHV几何形状下的非定常三维流动；2)在MPHV流动模拟中开发和实现能够准确预测生理雷诺数下脉动流向湍流过渡和再分层的先进湍流闭合模型；3)进行详细的实验室实验，获得全面的数据集，并利用这些数据集对CFD模型进行验证和微调；4)应用CFD方法详细研究双叶MPHV设计中的湍流结构，并探讨其对临床观察并发症的影响。所提出的CFD方法将彻底改变当前的阀门设计和测试实践。该方法将能够在目前仅通过实验无法获得的详细程度上描述阀门流场，从而在研发阶段节省大量时间和成本。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.