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

主要研究人员和他的同事使用基于实验的计算方法来模拟大型狭窄动脉中的血液流动，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流动和动脉壁行为。利用与牛颈总动脉相近的水凝胶管，实验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。这导致了一系列基于实验测量的考虑流体-壁面相互作用的三维非线性计算模型。采用任意拉格朗日-欧拉公式处理自由运动边界。流体模型的求解采用了隐式方法，包括SIMPLER算法和基于交错网格的无网格广义有限差分全耦合方法、迎风技术和一致的物理内插技术。介绍了一系列基于实验的薄壁和厚壁模型，以模拟大应变、变形、压缩和坍塌的狭窄管壁的动力非线性特性。采用增量边界迭代法和欠松弛技术处理流体-壁面相互作用，经实验数据验证，所得结果具有生理相关性，可为相关心血管疾病的早期检测、诊断和预防提供有用的信息。所建立的模型和数值方法适用于广泛的流固耦合问题，并可扩展到包括传质、动脉和斑块的结构、内皮反应和动脉重塑。狭窄是一种血管收缩，在西方世界是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相结合，以建立大型狭窄动脉中的血液流动模型，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流动和动脉壁行为。由于动脉结构的高度复杂性及其非线性力学性质、强烈的血液和动脉相互作用以及严重狭窄导致的临界血流条件，这一问题是困难的。用牛颈动脉和水凝胶管实验测定了狭窄动脉的动力学特性，其特性与牛颈动脉相近。在实验测量的基础上，用一种新的数值方法求解了一系列具有流体-壁面相互作用的三维非线性计算模型，以量化动脉压迫和斑块帽破裂的条件。经实验数据验证，这些结果有助于心血管相关疾病的早期发现、诊断和预防。所建立的模型和数值方法适用于各种具有流固耦合和复杂几何形状的问题。该模型可以扩展到包括质量传递、动脉和斑块的结构、移植物和支架、内皮反应和动脉重塑。作为生物技术的应用，所得结果可用于改进移植物和支架等医疗器械的设计。

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.