Author(s)

H.A. Ahmed, A. Sharif & M. Ghadiri

Abstract

This paper presents the numerical results of the hydrodynamic drag force acting on a spherical particle positioned in an accelerated flow of Newtonian fluids inside a converging circular (tapered) tube. The sphere is located on the axis of the tube in a pressure-driven parabolic Poiseuille-type flow. The computations have been performed using the finite volume based commercial package FLUENT 5. The standard contraction diameter ratio of 10:1 and three half-angle values, lo", 20" and 30"have been considered. The ratio of the sphere radius to the downstream tube radius, a/R2, is= 0.2. The computations were carried out for creeping flow regime (particle Reynolds number based on the particle diameter and maximum velocity at downstream section, Re2= 0.01). The results are presented in terms of the wall correction factor, K, which is defined as the ratio of the drag force on the sphere at a given separation distance to that on the sphere m an unbounded fluid (Stokes force). The separation distance is defined as the distance between the center of the sphere and the inlet of the conical section of the tube. Results show that the hydrodynamic drag force acting on a spherical particle at various separation distances increases substantially especially towards the exit.

Keywords