Numerical simulation of pressure-driven flow of solid bodies in Newtonian and Oldroyd-B fluids

Solid conveyance through a pipe and sedimentation or fluidization of particles are flows with wide industrial relevance. To understand the dynamics under such flow conditions we have studied the motion of large number of solid particles in Newtonian and Oldroyd-B fluids subjected to a pressure gradient using two-dimensional finite element simulations. The numerical scheme solves the entire fluid momentum equation without neglecting any terms. The particles can be neutrally or non-neutrally buoyant. Gravity acts along the axis of the channel. Based on our simulations we found that the ratio of the applied pressure gradient and the pressure gradient at fluidization is the most important flow parameter which helps to identify four basic flow regimes. Each of these flow regimes were seen to be affected by various flow parameters. Fluid elasticity induced stronger migration of the particles towards the center of the channel. It also caused less mixing of the particles. The suspension formed prominent microstructures, such as chains, in viscoelastic fluid and cross-stream arrays in Newtonian fluids when there were few particles in the channel. For large number of particles in the channel there was greater tendency to form clusters. Inertia of the fluid and the particles enhanced the mixing and agitation in the channel.