Axisymmetric motion of capsules through cylindrical channels
Axisymmetric motion of capsules through cylindrical channels
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DOI：
10.1017/s0022112097006587
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发表时间：
1997-10
影响因子：
3.7
通讯作者：
C. Quéguiner;D. Barthès-Biesel
中科院分区：
文献类型：
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作者：
C. Quéguiner;D. Barthès-Biesel
采用边界积分法对胶囊进入孔隙的流动进行了模拟。在胶囊和孔轴重合的地方考虑轴对称构型。航道为双曲线进出口区的圆柱体。该胶囊具有盘状的无应力形状，充满了牛顿液体，并被具有各种弹性性质(新胡肯或区域不可压缩)的非常薄的薄膜所包围。内囊液体和悬浮液的运动由Stokes方程控制，其解表示为边界积分。这些点是通过配置法计算的，其中点分布在胶囊界面上、流道壁上以及流动区域的入口和出口部分上。胶囊界面力学遵循弹性膜大变形理论。数值模型采用正向时间步长方法，在每个时间步长计算胶囊的位置和变形。该模型允许研究一些参数(胶囊的大小和几何形状、膜的弹性性质)对流动的影响。确定了气孔的入口长度、平衡时的稳定附加压降和胶囊的变形轮廓。研究发现，胶囊进入孔洞对下游条件不敏感；但达到稳定条件所需的管子长度强烈地取决于胶囊的大小和膜的特性。据预测，带有新胡肯薄膜的胶囊将通过连续拉伸现象发生破裂。带有抗面积膨胀膜的胶囊的流动很大程度上取决于颗粒的大小和形状。
A boundary integral method is used to model the flow of capsules into pores. An axisymmetric configuration is considered where the capsule and the pore axis coincide. The channel is a cylinder with hyperbolic entrance and exit regions. The capsule has a discoidal unstressed shape, is filled with a Newtonian liquid and is enclosed by a very thin membrane with various elastic properties (neo-Hookean or area-incompressible). The motion of the internal capsule liquid and of the suspending fluid is governed by the Stokes equations whose solution is expressed as boundary integrals. Those are computed by a collocation technique, where points are distributed on the capsule interface, on the channel walls and on the entrance and exit sections of the flow domain. The capsule interface mechanics follow the theory of large deformations of elastic membranes. The numerical model uses a forward time-stepping method, where the position and the deformation of the capsule are computed at each time step. The model allows the study of the effect of a number of parameters (capsule size and geometry, membrane elastic properties) on the flow. The entrance length in the pore, the steady additional pressure drop at equilibrium and the capsule deformed profiles are determined. It is found that the entrance of a capsule into a pore is not sensitive to downstream conditions; but the length of tube necessary to reach steady conditions depends strongly on capsule size and membrane behaviour. Bursting of capsules with a neo-Hookean membrane is predicted to occur through a phenomenon of continuous elongation. The flow of a capsule with a membrane that resists area dilatation depends strongly on particle size and shape.