Computational Modeling of Mechanical Heart Valves

描述(申请人提供)：目前机械人工心脏瓣膜(MPHV)的设计远远不是理想的，并且通常在植入后出现严重的并发症，如溶血、血小板破坏和血栓栓塞症。这些病理情况被认为是由于机械假体附近复杂的湍流流场导致血液成分暴露在过度的血液动力学应力下造成的。因此，改进和进一步改进现有MPHV设计的关键前提是深入了解它们所引起的流场。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，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。拟议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来模拟现实双叶MPHV几何形状中的非定常三维流动；2)在MPHV流动模拟中开发和实施先进的湍流闭合模型，该模型能够准确地预测生理雷诺数下脉动流动向湍流的转变和再分层；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，并探讨其对临床观察到的并发症的影响。建议的CFD方法将彻底改变目前的阀门设计和测试实践。该方法将能够以目前仅通过实验无法获得的详细程度描述阀门流场，从而在研究和开发阶段节省大量时间和成本。这项工作还将产生一个计算框架，用于评估植入给定MPHV设计可能导致血栓栓塞症并发症的可能性。

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.