脉动式血泵流固耦合问题的大涡模拟研究

Heart disease is one of the leading causes of death in the world. Due to a shortage in donor organs artificial hearts can be a bridge to transplantation or even serve as a destination therapy for patients with terminal heart insufficiency. Artificial hearts are mechanical blood pumps. Pulsatile pumps are very similar to human heart and do a better job at reproducing physiological blood flow. The flow in pulsatile pumps is unsteady, and with Reynolds number varying from 0 to about 3300 it is likely to be transitional or turbulent. The flow is driven by a flexible sac, therefore, it is an flow-structure interaction (FSI) problem in nature. Computational fluid dynamics (CFD) can assist experiment studies and capture more details in the flow field which experimental techniques are unable to detect. The current study aims at developing a robust and reliable large-eddy simulation (LES) technique combined with the immersed-boundary (IB) technique for low-Reynolds number internal flows. This project is then structured as follows: developing an accurate LES technique, employing high-order spatial schemes and adaptive mesh refinement (AMR) technique; validating the over a few selected benchmark cases; applying a unified mathematical framework of IB method to describe and simulate the FSI problem in a pulsatile pump. The final goal of this study is to development a reliable and robust numerical tool for a better understanding of the flow physics and blood damage in blood pumps, and ultimately to assist the design of the blood pumps.

心血管疾病是威胁人类健康的最常见疾病。心室辅助装置（俗称人工心脏）是机械式血泵，可以替代/辅助心脏或者过渡到心脏移植，正成为应对心脏病的重要手段。脉动式血泵类似于自然心脏，里面的流动本质上是非定常的转捩/湍流脉动流动，并有流固耦合的问题。数值模拟可以弥补实验的不足，捕捉更多的流场细节。本项目致力于采用大涡模拟 (LES) 技术和浸入边界 (IB) 方法，模拟脉动式血泵内流固耦合问题，并发展一套用于低雷诺数内流动的三维LES & IB计算程序。本研究主要分为以下几点内容：发展适用于低雷诺数内流动的LES技术，结合IB方法并采用主流的亚格子模式、高精度的数值格式和自适应网格技术捕捉流动细节；对程序进行有效的算例验证；运用该程序整体模拟脉动式血泵内的流固耦合问题。最终将开发一套成熟的数值模拟工具，以加深对血泵内流场细节的理解，并辅助估算、预测血液损坏和改进血泵的设计。

心血管疾病是威胁人类健康的最常见疾病。心室辅助装置（俗称人工心脏）是机械式血泵，可以替代/辅助心脏或者过渡到心脏移植，正成为应对心脏病的重要手段。在血泵等血液接触型人工器官的开发过程中，计算流体力学结合溶血经验预测模型已被广泛用于预测溶血量以及辅助血液相容性设计。这类装置内的流场极其复杂，可能是层流、过渡流或湍流。因此溶血的准确预测不仅有赖于溶血经验模型的精度，也有赖于复杂流场的准确预测。本研究从改善湍流流场的预测、改进溶血经验模型等角度进行了系统性研究，开发了可求解三维复杂湍流流动的大涡模拟计算程序，并采用大涡模拟改善了对血泵内复杂流场的预测；提出了基于能量耗散的溶血经验预测模型，并进行了广泛的验证，相较传统的基于雷诺应力的溶血模型，新模型显著改善了溶血预测精度。本项目的研究将为加强对血泵内复杂流场的认识，提高溶血预测精度，改进血泵的血液相容性设计有重要的理论意义和实际应用前景。