Velocity and wall-shear stress measurements of pulsatile flow of blood-analog fluids in elastic vessels

目前，人类血管的病理变化是现代医疗保健系统面临的主要挑战之一。在这种情况下，弹性血管中的脉动血流和由此产生的壁面剪切应力分布是影响动脉硬化机制的主要因素之一，从而影响动脉狭窄的发展。因此，从医学的角度来看，准确预测人血管内的流场和非定常壁剪切应力对于评估手术指征或选择最有希望的手术干预措施至关重要。为此，有必要详细分析脉动流与弹性容器的流固耦合问题。从流体力学的角度来看，该问题的特点是周期性流动，具有复杂几何形状的容器，以及非牛顿流体通过随时间变化的壁剪应力分布与弹性容器壁的相互作用。然而，流体的非牛顿流变性能通过非定常周期性壁面剪切应力和剪切速率对流动力学性能产生显著影响的假设尚未得到研究。这是本建议的范围，以高空间和时间分辨率的实验分析非牛顿，血液模拟流体和弹性血管的脉动流动之间的流-结构相互作用。在生理流动条件下，以高时间分辨率在空间上确定直弹性血管和弯曲弹性血管以及对称分岔的扩张和流场，并量化FSI对速度场、血管扩张和壁面剪切应力分布的影响。

Nowadays, pathological changes of human blood vessels are one of the major challenges of the modern health care system. In this context, the pulsating blood flow in elastic blood vessels and the resulting wall-shear stress distribution is one of the main factors that influences the mechanisms of arteriosclerosis and, hence, the development of arterial stenosis. Thus, from a medical point of view, precise predictions of the flow field and the unsteady wall-shear stress in human blood vessels are extremely important to assess the indication for surgery or to choose the most promising surgical intervention. For this, it is essential to analyze in detail the underlying problem of the fluid-structure interaction (FSI) of a pulsatile flow and an elastic vessel. From a fluid-mechanical perspective, this problem is characterized by a periodic flow, a vessel with complex geometry, and the interaction of a non-Newtonian fluid with the elastic vessel walls via the time-dependent wall-shear stress distribution. However, the hypothesis that the non-Newtonian rheological behavior of the fluid possesses a significant influence on the FSI via the unsteady periodic wall-shear stress and shear rate has not been investigated yet. It is the scope of this proposal to analyze the fluid-structure interaction between a pulsatile flow of a non-Newtonian, blood-analog fluid and an elastic vessel experimentally with high spatial and temporal resolution. The dilatation of and the flow field in straight and curved elastic vessels as well as symmetrical bifurcations will spatially be determined at high temporal resolution for physiological flow conditions, and the impact of the FSI on the velocity field, the vessel dilatation, and the wall-shear stress distribution will be quantified.