Experiment-Based 3-D Computational Studies of Blood Flow in Stenotic Carotid Arteries with Dynamic Wall Properties

首席研究员和他的同事们使用一种基于实验的计算方法来模拟大狭窄动脉的血流，并研究可能导致动脉压迫、斑块破裂、中风和心脏病发作的临界血流和动脉壁行为。用水凝胶管测定了具有斑块硬度和几何变化的狭窄动脉的动力学特性，其力学特性接近于牛颈动脉。这导致了一系列基于实验测量的流体-壁相互作用的三维非线性计算模型。用任意拉格朗日-欧拉公式处理自由移动边界。隐式方法包括更简单的算法和基于交错网格的无网格广义有限差分的完全耦合方法，逆风技术和一致的物理插值技术用于求解流体模型。介绍了一系列基于实验的薄壁和厚壁模型，用于模拟具有大应变、大变形、大压缩和大坍塌的狭窄管壁的动态非线性特性。采用增量边界迭代法和欠松弛技术处理流壁相互作用。经实验数据验证，所得结果具有生理学相关性，可为相关心血管疾病的早期发现、诊断和预防提供信息。所开发的模型和数值方法适用于流体-结构相互作用的广泛问题，并且可以扩展到包括质量转移，动脉和斑块的结构，内皮反应和动脉重塑。血管狭窄是一种血管收缩，是西方世界导致死亡的主要原因之一。研究人员和他们的同事将实验与计算模型结合起来，模拟大狭窄动脉的血流，并研究可能导致动脉压迫、斑块帽破裂、中风和心脏病发作的临界血流和动脉壁行为。由于动脉结构的高度复杂性及其非线性力学特性，强烈的血液和动脉相互作用以及严重狭窄引起的临界流动条件，该问题很困难。用牛颈动脉和水凝胶管实验测定了狭窄动脉的动态特性，水凝胶管的特性接近于牛颈动脉。在实验测量的基础上，通过一种新的数值方法求解了一系列具有流体-壁相互作用的三维非线性计算模型，以量化可能发生动脉压迫和斑块帽破裂的条件。实验数据验证了上述结果，有助于心血管相关疾病的早期发现、诊断和预防。所开发的模型和数值方法适用于具有流固相互作用和复杂几何形状的广泛问题。该模型可以扩展到包括质量转移、动脉和斑块结构、移植物和支架、内皮反应和动脉重塑。作为生物技术的应用，所获得的结果可用于改进诸如移植物和支架等医疗设备的设计。

The principal investigator and his colleagues use anexperiment-based computational approach to model blood flow inlarge stenotic arteries and investigate critical flow and arterywall behaviors that may lead to artery compression, plaque caprupture, stroke and heart attack. Dynamic properties of thestenotic arteries with plaque stiffness and geometry variationsare determined experimentally using hydrogel tubes whosemechanical properties are close to those of bovine carotidarteries. This leads to a series of 3-D nonlinear computationalmodels with fluid-wall interactions based on the experimentalmeasurements. Arbitrary Lagrangian-Eulerian formulation is usedto deal with free moving boundaries. Implicit methods includingthe SIMPLER algorithm and fully coupled methods based onmesh-free generalized finite differences with staggered grids,upwind techniques, and a consistent physical interpolationtechnique are used to solve the fluid model. A sequence ofexperiment-based thin- and thick-wall models are introduced tomodel the dynamic nonlinear properties of the stenotic tube wallwith large strain, deformation, compression and collapse. Anincremental boundary iteration method and an under-relaxationtechnique are used to handle the fluid-wall interactions.Validated by experimental data, results obtained arephysiologically relevant and may provide information helpful forearly detection, diagnosis and prevention of relatedcardiovascular diseases. The models and numerical methodsdeveloped are applicable to a wide range of problems withfluid-structure interactions and can be extended to include masstransfer, structures of arteries and plaques, endothelialresponses, and arterial remodeling. Stenosis, a constriction in blood vessels, is one of theleading causes of death in the western world. The investigatorsand their colleagues couple experiments with computations tomodel blood flow in large stenotic arteries and investigatecritical flow and artery wall behaviors that may lead to arterycompression, plaque cap rupture, stroke and heart attack. Theproblem is difficult because of the high complexity of arterystructure and its nonlinear mechanical properties, strong bloodand artery interactions, and critical flow conditions caused bysevere stenosis. Dynamic properties of the stenotic arteries aredetermined experimentally using bovine carotid arteries andhydrogel tubes, whose properties are close to those of bovinecarotid arteries. A series of 3-D nonlinear computational modelswith fluid-wall interactions, based on the experimentalmeasurements, are solved by a novel numerical method to quantifyconditions under which artery compression and plaque cap rupturemay occur. Validated by experimental data, these results can behelpful for early detection, diagnosis and prevention of relatedcardiovascular diseases. The models and numerical methodsdeveloped are applicable to a wide range of problems withfluid-structure interactions and complex geometries. The modelscan be extended to include mass transfer, structures of arteriesand plaques, grafts and stents, endothelial responses andarterial remodeling. As applications of biotechnology, theresults obtained can be used to improve the design of medicaldevices such as grafts and stents.