Interaction of Elastic Vessel Wall and Arterial Blood Flow

本文用激光多普勒测速仪（LDA）研究了血管壁弹性对血液流动特性的影响。在离体实验中，我们设计了一种能产生充分发展的脉动流的流动装置，其雷诺数和频率参数可在与人体大动脉血液流动相对应的范围内改变。选择直径为15 mm、长为4.3 m的流管，以产生雷诺数高达5000的发展流。通过旋转鞘管和流管出口处的狭缝产生非零平均流量的脉动流。用二维LDA系统测量了管内的流速，并通过遍历LDA系统得到了管内截面上的流速分布。用电磁流量计测得的流量所对应的Poiffille速度剖面很好地代表了定常流动条件下的速度剖面 ...更多信息 流量计，显示流量已充分发展。脉动流条件下的速度分布显示，在最小流量阶段，尽管总流量在脉动期间始终为正值，但在管壁附近存在流动反转。在加速阶段的速度剖面中也观察到拐点。脉动速度剖面的这些特征与不可压缩流体通过直圆柱体的非定常流动的理论预期吻合得很好。在体实验中，用光纤激光多普勒测速显微镜（FLDAM）研究了大鼠（SHR和WKY）肠系膜微血管血流脉动与微血管流变学和网络拓扑结构的关系。SHR肠系膜微血管血流相对于颈动脉压的相位滞后随微动脉直径的减小而增大，而WKY微血管血流相对于颈动脉压的相位滞后随微动脉直径的减小而增大。本文用模拟微血管树的多孔锥形弹性管模型对微动脉中的血流脉冲传播进行了理论分析，并对实验结果进行了分析。结果表明，SHR和WKY微血管中的微动脉长度较WKY长，分支点较少，可能是两者之间存在差异的原因。还在直径为10至30 μ m的小动脉中测量了流动脉冲的传播速度，以估计单个血管的弹性特性。传播速度为10 cm/s的数量级，并随着血管直径的增加而增加，这也与多孔锥形弹性管模型的预测一致。少

Effects of the elasticity of the vessel walls on the blood flow characteristics are studied in vitro and In vivo using laser-Doppler anemometers (LDA).In in vitro experiments, a flow apparatus was devised to produce a fully developed pulsatile flow of which Reynolds number and frequency parameter can be vaded for the ranges corresponding to those of the blood flow In the human large arteries. The flow tube was chosen to be 15 mm In diameter and 4.3 m long to produce the developed flow for the Reynolds number up to 5000. The pulsatile flow with non zero mean flow rate is generated by a rotating sheath and a slit put at the outlet of the flow tube. The flow velocity was measured by a 2-dimensional LDA system and the velocity profiles over the cross-section of the tube are obtained by traversing the LDA system. The velocity profile obtained under a steady flow condition was well represented by the Poiseuille velocity profile corresponding to the flow rate measured by an electromagnetic fl … More ow meter, which shows the flow was fully developed. The velocity profiles under a pulsatile flow condition showed a flow reversal near the tube wall in the phases of minimum flow although the total flow rate was always positiv during the pulsation period. Inflection points were also observed In the velocity profiles at the acceleration phases. These features of the pulsatile velocity profiles agree well with the theoretical expectations for the unsteady flow of an incompressible fluid through a straight circular cylinder. Elastic tube highly transparent for the measurement with LDA was made from polyurethane and the velocity measurement inside the elastic tube is in progress.In in vivo experiments, pulsation of the blood flow was studied in microvessels of the mesente ry of rats (SHR and WKY) by a fiber-optic laser-Doppler anemometer microscope (FLDAM) in relation to the rheology and the network topology of the microvessels. The phase lag of the microvascular flow relative to the carotid arterial pressure increased with decreasing diameter of arterioles in SHR mesentery, while there was little correlation between them In WKY. The propagation of the flow pulse In arterioles was theoretically treated by a porous tapered elastic tube model simulating the microvascular tree and the experimental results were analyzed based on this model. It was suggested from the model that the difference observed in the flow pulsation between SHR and WKY might be due to the longer arteriolar length and the fewer branch points in the SHR microvasculature than WKY. The velocity of the propagation of the flow pulse was also measured in arterioles with diameters from 10 to 30 mum to estimate the elastic property of single vessels. The propagation velocity was in the order of 10 cm/s and increased with the increasing vessel diameter, which is also consistent with the prediction derived from the porous tapered elastic tube model. Less