| This dissertation is concerned with computational simulations of gas-solid and gas-liquid flows.;For the studies of gas-liquid flows, the unsteady laminar Navier-Stokes equation was solved in each phase using a fixed Eulerian grid, and the Volume of Fluid (VOF) technique was used to account for tracking the gas/liquid interface. As a benchmark, a two-dimensional computational model of a moving ridge on a surface due to a wettability gradient was studied, and the velocity of the ridge along the surface was compared with the analytical expression of Brochard (1989). Several computer simulations for the motion of liquid drops through 2D and 3D fabrics under different conditions such as the distance between fibers, contact angle distribution, and drop initial velocity were performed to identify the key issues for penetrating a liquid drop through a fabric.;For the gas-solid studies, the interaction of spherical solid particles with turbulence in a fully developed turbulent channel flow was studied. The Eulerian framework was used for the gas-phase, whereas the particle-phase was treated via a Lagrangian point of view. The time-dependent three-dimensional Navier-Stokes equations were numerically solved using direct numerical simulation (DNS) via a pseudospectral technique. The Lagrangian particle equation of motion included the wall-corrected nonlinear drag force, and the wall-induced and shear-induced lift force. To have a better understanding of the mechanisms governing the interaction of particles with their surroundings, one-way, two-way and four-way coupling approaches were taken into consideration. The influence of particles on the flow was modeled by distributing the particle feedback force on the computational grid points. The hard sphere particle-particle collision model based on the assumption of binary collisions was implemented in the analysis. In the case of one-way coupling, the numerical predictions were compared with the existing simulation results and favorable agreement was achieved. Several simulations for different particle relaxation times and particle mass loadings were performed. For the size ranges considered, the numerical predictions showed that the addition of particles attenuates the intensity of fluid turbulence fluctuations and as particle mass loading increases, the level of attenuation increases. It was shown that inter-particle collisions increased the particle deposition velocity as particle mass loading increased, while two way coupling decreased the particle deposition rate. In the physical case (four way coupling), the particle deposition velocity increased compared with the one way coupling case. For high inertial particles (70 mum copper particles), inter-particle collisions dominated the behavior of particles, while two-way coupling had no significant effects on particle phasic fluctuations. |
