Hemodynamic parameters on the macromolecular transport between serum and blood vessel wall

1.腹主动脉瘤模型中的脉动流和壁应力：用流动显示方法研究了模拟梭形和外侧囊状动脉瘤的玻璃模型中的脉动流。在加速相的初始阶段，血流开始与动脉瘤近端壁分离。然后，分离的气泡或漩涡迅速增大，并沿周向充满整个动脉瘤区域。在这段时间内，漩涡中心从动脉瘤的近端移动到远端。例如，可能发生在射血期结束时的瞬时反向流在动脉瘤壁和中心涡流之间通过。当流速和脉动频率较高时，旋涡在动脉瘤远端破裂成湍流。当动脉瘤的长度增加时，观察到相同的效果。脉动幅度的减小使流态更接近T型 ...更多信息 帽子在稳定的流动。本文对脉动流通过轴对称膨胀管的速度场和压力场进行了有限元分析。计算得到的速度场和流线的瞬态图形与实验结果吻合较好。涡在扩张段的出现、消失及其发展导致了复杂的压力场和剪切场分布。当流速达到最大值时，壁面切应力的局部最小值和最大值出现在扩张远端的上游和下游。通过对动脉瘤模型施加壁面剪应力和压力，数值研究了动脉瘤模型的壁面应力分布。它取决于压力而不是壁面剪应力。壁面剪应力集中主要发生在中、远段之间.通过人颈动脉的脉动流：进行可视化实验以阐明通过透明的人颈动脉的脉动流中的复杂流动模式。在脉动流中，通过本研究中使用的所有分叉，观察到螺旋再循环流的模式类似的马蹄涡周围壁基突起在圆管中产生的。在雷诺数大于100的定常流动中，马蹄涡也出现在人颈总动脉分叉处。时变流动也主要在减速阶段产生马蹄涡。在产生螺旋流的同时，在顶点上游的壁面上出现了驻点。它们的位置取决于单个动脉中分支之间的流量分配比。在分支血管的外壁或内壁观察到分离泡。在动脉分支部位进行垂直于管轴的管壁应力分析。内外壁在拱线上有拉压现象。血管壁力学性质与动脉病变的定量关系是今后研究的重点。少

1. Pulsatile Flow and wall stress in Models of the Abdominal Aortic Aneurysm: Pulsatile Flows in glass models simu-lating fusiform and lateral saccular aneurysms were investigated by a flow visualization method. At the initial stage of accelerating phase, the flow began to separate from the proximal wall of the aneurysm. Then the saparate bubble or vortex grew rapidly in size and filled the whole area of the aneurysm circumferentially. During this period of time, the center of the vortex moved from the proximal end to the distal point of the aneurysm. The transient reversal flow, for instance, which may occur at the end of the ejection period, passed between the wall of the aneurysm and the centrally located vortex. When the rate and pulsatile frequency of flow were high, the vortex broke down into turbulence at the distal portion of aneurysm. The same effect was observed when the length of the aneurysm was increased. A re-duction in pulsatile amplitude made the flow pattern close to t … More hat in steady flow. A finite element analysis was made to obtain velocity and pressure fields in pulsatile flow through a tube with an axisymmetric expansion. Caluculated in stantaneous patters of velocity field and stream lines agreed well with the experimental results. The appearance and disapperance of the vortex in the dilated portion and its development resulted in complex distributions of pressure and shear fields. Locally minimum and maximum values of wall shear stress occured at points just upstream and down stream of the distal end of the expansion when the flow rate reached ist peak. Wall stress distribution was investigated nu-merically as the result of loading wall shear stress and pressure on inner wall of the aneurysm model. It was depended upon presuure than wall shear stresss loading. The shear stress concentration in the wall was generated between middle and distal portion of the aneurysm.2. Pulsatile Flow Through the Human Carotid Arteries: Visualization experiments were performed to elucidate the complicated flow pattern in pulsatile flow thorugh the human carotid arteries which were made transparent. Helically recirculating flow with a pattern similar to that of the horseshoe vortex produced around wall-based protuberances in circular tubes was observed in pulsatile flow through all the bifurcations used in the present study. The horseshoe vortex has also been demonstrated to occure at the human common carotid bifurcation in steady flow with reynolds number above 100. Time-varying flows also produced the horseshoe vortex mostly during the decelerating phase. While this helical flow was produced, the stagnation points appeared on the wall upstream of the apex. Their position was dependent upon the flow distribution ratio between braches in the individual arteries. A separation bubble was observed at the outer or inner wall of the branch vessels.3. Stress analysis in the wall perpendicular to tube axis was performed at arterial branch site. Tension and compressionwere seen at the inner and outer wall on the line of apsides. The more attension toward quantiating the relationship between the mechanical properties of the vessel wall and arterial disease is disired in the future study. Less