Numerical simulation of particulate flows and turbulent wavy core-annular flows

This thesis presents numerical studies on the motion of particulate flow in Newtonian fluid and an Oldroyd-B fluid and of turbulent wavy core-annular flow with highly viscous fluids. The several correlations of lift-off is obtained from results of numerical simulation for particulate flow. The results of wavy core-annular flow agree well with experimental data. Chapter 2 studies the lift-off to equilibrium of a single circular particle in Newtonian and viscoelastic fluids by direct numerical simulation. The critical Reynolds number for lift-off condition is obtained as a function of gravity Reynolds number. The multiple equilibrium positions are observed on Newtonian fluid and even in Oldroyd-B fluids. The equilibrium height increases with the Reynolds number, the fluid elasticity and the slip angular velocity of the particle. Chapter 3 performs the simulation of the motion of 300 particles in plane Poiseuille flows of Newtonian fluids. The equilibrium height of the particle bed increases as the shear Reynolds number. An engineering correlation, which is used to estimate the critical shear Reynolds number for the lift-off of many particles, is obtained from the numerical data.; Chapter 4 studies the multiple equilibrium positions in single particle lift-off in plane Poiseuille flows of Newtonian fluid and Oldroyd-B fluids in further detail. We find that at a given channel Reynolds number there are regions inside the channel in which no particle, irrespective of its weight, fluid elasticity and channel width, can attain a state equilibrium position. This would result in particle depleted zones in a channel with Poiseuille flows of a dilute suspension of particles of varying densities. We study also the effects of the channel width and fluid elasticity on equilibrium diagram. Chapter 5 performs the finite element method simulation of turbulent wavy core-annular flows using k-ω turbulent model. The wavelength decreases with Reynolds number and volume ratio, whereas the pressure gradient increases with them. The computed wave shapes and frictional loss are in satisfactory agreement with experiments and are a great improvement from the previous results.