The horseshoe vortex: a secondary flow generated in arteries with stenosis, bifurcation, and branchings.
The horseshoe vortex: a secondary flow generated in arteries with stenosis, bifurcation, and branchings.
复制标题
马蹄涡：狭窄、分叉和分支的动脉中产生的二次血流。
作者：
T. Fukushima;T. Azuma
为了阐明动脉血流的流体动力学特征，本研究采用各种透明血管模型进行血流可视化研究，这些血管模型有凸起、分叉或分支。观察到的流动模式可以通过二次流的出现来理解，称为马蹄涡。马蹄形涡在有突起突起的管状边界层中产生的模式解释如下：由于粘性剪切流与管壁的相互作用，在凸起的上游表面产生了径向压力梯度。这种压力梯度使流体颗粒直接在障碍物前向下旋转。然后，它们绕在自己身上，形成了一个被束缚的漩涡管，即马蹄形漩涡，它依次从两个方向绕过突起的前部。在具有y形分叉或矩形侧分支的管中，分支处的分流器取代了突起，产生了类似马蹄形涡的涡流管。旋涡管从高压区即分流器顶端向低压区即分支孔侧缘延伸，在主管和分支管内产生旋涡二次流。这些结果表明，以下机械因素可能启动或促进动脉粥样硬化和血栓形成：马蹄涡捕获的血细胞与血管壁的碰撞，湍流引起的血管壁和血细胞的相互作用，以及局部高壁剪切应力的发生。
In order to elucidate the fluid dynamic feature of arterial blood flow, the present flow visualization study was carried out with various transparent blood vessel models having a protuberance, a bifurcation, or branchings. The observed flow patterns could be understood in terms of occurrence of a secondary flow, named the horseshoe vortex. The mode of generation of the horseshoe vortex in a tube with a protuberance projecting into the boundary layer was explained as follows. A radial pressure gradient toward the tube wall was produced along the upstream surface of the protuberance because of the interaction between the viscous sheared flow and the wall. This pressure gradient made fluid particles turn round downward directly before the obstacle. Then they curled round on themselves and formed a bound vortex tube, the horseshoe vortex, which in turn passed round the front of the protuberance in both directions. In a tube with a Y-shaped bifurcation or rectangular side branch, the flow divider at the branching site acted in place of the protuberance to produce a vortex tube similar in pattern to the horseshoe vortex. The vortex tube extended from the high pressure region, i. e. the apex of the flow divider, to the low pressure region, i. e. the lateral margin of the branch orifice, and generated swirling secondary flows in the main and branched tubes. These results suggested that the following mechanical factors might initiate or facilitate athero- and thrombogenesis: collision of blood cells captured by the horseshoe vortex with blood vessel walls, the interaction of the walls and blood cells due to turbulence, and the occurrence of localized high wall shear stresses.