竖直毛细管中有限长液柱的粘性流体运动
The Motion of Viscous Liquid Cylinder with Finite Length in a Vertical Capillary Tube
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摘要: 本文考虑了竖直毛细管中具有两个自由面的有限长液柱的粘性流体运动.假设流体是牛顿的对边界条件进行线性化后,得到了小雷诺数情形下速度、压力和自由面形状的级数形式的分析表达式,对水和血液在多种液柱长度下求出了数值结果.分析表明在上下弯月面处有强回流.最大回流速度可达主流平均速度57%左右此外,本文还研究了惯性效应.采用时间相关的有限差分法求出了Re=24.5时非线性方程的数值解.将此数值解和小雷诺数时的分析解进行比较表明,当Re≤24.5时惯性效应不大.Abstract: This paper deals with the motion of viscous liquid column with finite length and two free surfaces in a vertical straight capillary tube. It is assumed that fluid is Newtonian. Linearizing the boundary conditions, analytic expressions in the form of infinite series have been obtained for velocity, piessure and free surface at low Reynolds number. The numerical calculation is carried out for a set of cylinder's length of water and blood. It has been revealed that there are considerable circulating currents at the upper and lower meniscuses. Its maximum velocity is about 57% of the average velocity of the mainstream. Inertial effect is also studied in this paper. Using the time-dependent method in finite difference techniques, numerical solution of the corresponding nonlinear equation at Re<24.5 is computed. Comparing it with analytic exact solution at low Reynolds number shows that inertial effect is negligible provided Re<24.5.
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[1] Lew,H.S.and Fung,Y.C.,Biotheology 6(1969) 109-119. [2] Roache,P.J.,Computational Fluid Dynamics(1972).
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