Computer modeling of granular and two-phase turbulent flows

This thesis focuses on developing a computational model for analyzing rapid granular and turbulent two-phase flows in various regions. In this work, a computational scheme for simulating dry frictional granular chute flows is developed. A kinetic-based model which includes the frictional energy loss effects is used, and the boundary conditions for a bumpy wall with small friction are derived by ensuring the balance of momentum and energy. At the free surface, the condition of vanishing solid volume fraction is used. The mean velocity, the fluctuation kinetic energy and the solid volume fraction profiles are evaluated. It is shown that steady granular gravity flow down a bumpy frictional chute could be achieved at arbitrary inclination angles. The computational results also show that the slip velocity may vary considerably depending on the granular layer height, the surface boundary roughness, the friction coefficient and the inclination angles. A small friction coefficient and a smooth wall lead to a region of low density and high fluctuation energy in the neighborhood of the wall. For high friction coefficients and rough walls, the solid volume fraction increases monotonically up to the wall, while a region of low fluctuation energy is formed near the solid surface. The model predictions are compared with the existing experimental and simulation data, and good agreement is observed. In particular, the model can well predictate the features of the variation of solid volume fraction and fluctuation energy profiles for different particle-wall friction and restitution coefficients and wall roughness. Two-phase gas-particle turbulent flows at various loadings in vertical, horizontal and inclined channels and in a vertical pipe are also analyzed. Thermodynamically consistent two- phase turbulent flow models that account for the particle-particle collisions and the phasic fluctuation kinetic energy interactions are used, and a computational model for analyzing dilute and dense turbulent flows in ducts is developed. The governing equations for the gas-phase turbulence are upgraded to a two-equation low Reynolds number turbulence closure model that can be integrated directly to the wall. Two specific models are used in the analysis. The first model is isotropic and the equations governing the phasic fluctuation kinetic energy and dissipation rates resemble the extended k-epsilon type turbulence model. The second model is rate-dependent and anisotropic that allows capturing the anisotropy of particulate and fluid phase turbulent stresses. A no-slip boundary condition for the fluid phase and slip velocity boundary condition for the particle phase are used in both cases. The computational model is first applied to dilute gas-particle turbulent flows. The predicted mean velocity and turbulence intensity profiles are compared with various experimental data, and good agreement is observed. Examples of additional flow properties such as the phasic fluctuation energy, phasic fluctuation energy production and dissipation, as well as interaction momentum and energy supply terms are also presented and discussed.; Application of the model to relatively dense gas-particle turbulent flows are also described. The model predictions are compared with the experimental data of Miller and Gidaspow and reasonable agreement is observed. It is shown that flow behavior is strongly affected by the phasic fluctuation energy, and the momentum and energy transfer between the particulate and the fluid constituents.; For aerosol particles, a new two-fluid model for evaluating the particle deposition velocity in turbulent channel flows is described. The rate-dependent model is first used to calculate the components of particle turbulence intensities for gas-particle turbulent flows in a vertical channel. Then the model of Reeks (1983) and Guha (1997) is used for evaluating the particle wall deposition rates. Variations of particle deposition velocity with particle...