Numerical study of dynamics of mass-emitting particles in multi-phase flow

Abstract: Suspended particles can be found in wide range of industrial applications such as food industry, mining industry and energy conversion processes. Depending on flow cases which particles are involved, different dynamics and motions are expected from suspended particles. In addition, it is well-known that existence of particles alters the configuration of surrounding flow.Fuel particles are expected to be found to gasify or evaporate in energy conversion processes . Burning (or combustion) of a fuel particle results in the production of a thin film of gas on the surface of the particle. The flow around the particle and existence of the thin film due to the combustion, might be the source of changes in particle-particle interaction, particle interaction with the surrounding fluid and walls. In order to investigate these phenomena, we apply a radial outflow boundary condition on the surface of particles to resemble gasification/evaporation of solid particles or droplet fuels.To study the effect of outflow from the surface of particles, we consider two generic cases; particles in shear flow and sedimentation of particles. These cases have been studied thoroughly in literature in which both behavior of the particle and pattern of the surrounding flow has been investigated. This provides us an opportunity to analyze our results against these well studied cases. In agreement with previous studies, it is observed that the radial outflow results to a decrease in drag and lift forces and an increase in pressure on the surface of the particle. Thence, a growth in maximum velocity of settling spherical particle and a decay in angular velocity of rotating particle by increasing outflow rate can be observed. Furthermore, a general hindering effect in particles interaction is detected. Considering the configuration of the background flow, different flow streamlines lead to different particle trajectories in a simple shear flow, in existence of outflow from the surface of particles.In the last part of the thesis we consider 3D simulations of three-phase flow (gas-liquid-particle) in which particle and bubble are moving under external forces and interacting with each other. In this case, we apply a non-wetting boundary condition on the surface of solid particle. A compound consist of a particle entrapped inside a bubble, preforms different behaviors depending on the competition between gravitational and surface tension induced forces.Regarding the numerical method, we apply a lattice Boltzmann method (LBM) together with momentum exchange approach in order to couple particle and fluid. However, to capture phase interfaces in simulation of three-phase flows, a pseudo-potential method is considered .