人工血栓装置中粒子聚集机制的探讨

A model for the Gathering of Particles in the Artificial Thrombus Machine

在人工形成血栓的ｃｈａｎｄｌｅｒ环中血栓总是出现在前弯月面。对于这一奇特现象，人们长期困惑不解。本文提出一个简单模型，对竖直毛细管中有限长液柱内单个粒子的受力和运动情况进行了理论分析和数值计算。结果表明，该模型能模拟粒子在前弯月面聚集的现象，从而揭示出粒子聚集的主要原因之一是粒子在管壁附近受到一横向升力，使其离开原来的流线向轴心迁移，漂移到轴线附近的粒子又被向前的回流带到前弯月面附近，进而趋向一逗留点。计算显示了趋向逗留点的过程，并研究了几何尺寸、血流速度和粘度等参数对聚集的影响。这样，长期困惑不解的问题有了一清楚的力学解释。

In the artificial thrombus machines such as Chandler loop, the thrombus is alwaysformed at the frontal meniscus. This Phenomenon is amazing and puzzling for many years.Although people have known well about the fluid field in artificial thrombus machines , thereason why thrombus always forms at the specific position is still not clear.To study the mechanisrn of this phenornenon, we established a new model in which weconsider the blood as the nlixture of plasma and blood cells. The plasma is Newtonion andthe cells are simulated by particles. For the existance of the tube wall,the partice will notalways move with the liquid particle, but a little slower than the fluid , and more important-ly, the fluid and the tube wall will produce a lift force which causes the particle to keep awayfrom the walls. We assumes that the density of particles is low so that we can neglect the ef-fects of the particles while calculating the fluid field. From the dynamic equations of the par-ticle involving the lift force, we computed the motion of the particles. The results show thatno matter where the particle sets off, it will tend to a stationary position near the frontermeniscus, this indicates that the lift force is one of the main reason to cause the gathering ofblood cells at the fronter meniscus of the artificial thrombus machine. Since the gathering ofblood cells is a necessary event to form the thrombus, the lift force is very important to thethrombus formation in the machine, and it might be the working theory of the machines.This model are also applied for studying the effects of several factors, including the Reynoldsnumber, the viscosity of liquid, and the size of the particles, on the gathering of blood cellsand thrombus formation.