Radial Migration of Particles in Poiseuille Flow Using a Three Dimensional Resolved Discrete Particle Method
The objective of this study is to develop a relatively simple numerical technique that utilizes a three-dimensional immersed boundary-based method (IBM) to solve and enhance the understanding of three dimensional particles suspended in a viscous fluid flow through a circular tube. The motion of a single spherical particle in a Poiseuille flow is closely examined, and the simulation results are extensively compared with analytical, experimental and numerical results in the literature. New extensive correlations for the kinematic parameters of a neutrally buoyant spherical particle at equilibrium have been obtained in terms of the particle size ratio and flow Reynolds number. The hydrodynamic drag and lift on a spherical particle are investigated for the effects of the blockage ratio and particle-wall distance: A correlation for the drag on a sphere fixed at the central axis of a pipe flow that also takes the blockage ratio into account has been developed. The hydrodynamic pressures acting on moving spheres at their equilibrium positions have been elaborately presented. The cause of dual equilibrium positions has been attributed in this study to the weak rotational effects of particles on the existing "pressure wells" that occur in pipe flows; the limiting conditions for dual and unstable equilibrium to occur have been presented. The independent parameters controlling particle distribution, which are the size ratio, the flow Reynolds number, and the solid volume fractions have been systematically investigated for both monodisperse and polydisperse systems of spheres. Finally, studying the radial migration of non-spherical particles has resulted in new findings on the rotational behaviors for cones and ellipsoids (prolates and oblates), via the variation of parameters like aspect ratio, particle size, and initial particle orientation: Cones of aspect ratio "C-III" rotate in a "twisting-flip" mode, while spiraling in a tube for a given particle size and Re, with a frequency that increases with both the sphere size and flow Reynolds number.