Numerical modeling of conservative and particulate density currents

This research involved three individual but related problems in the field of conservative and particulate density current. These problems are (1) performance of different turbulence models in numerical simulations of particulate density current; (2) generation of internal waves in a stratified medium due to the presence of a density current; and (3) dynamics of turbidity current flowing through minibasins in the deep ocean. A two dimensional vertical structure finite volume model for conservative and particulate density current was developed. The Reynolds-averaged Navier-Stokes equations along with the sediment mass conservation equation were solved in a nonorthogonal structured grid system. For the closure of the Reynolds stresses terms, the one-equation k-l and q2-l model, and two-equation k-&egr; and q2-q2l models were incorporated in the numerical model.; The performance of different turbulence closure schemes in numerical simulations of particulate density current was investigated. All the turbulence schemes provided similar results when compared against laboratory experiment on depositional turbidity current. The turbulence closure schemes were also applied at large scale to study depositional and erosional turbidity currents. It was observed that the q2-q2l two-equation turbulence model can predict comparatively better mixing near the peak velocity region than the other schemes.; Investigation of the generation of internal waves in a stratified medium was conducted using the k-&egr; turbulence model. The model was verified against two sets of experiments. In one, the current was released on a horizontal bed and in the other, the current was released over a ramp. In both cases, the model captured the generation of internal waves and other aspects of the flow. To evaluate the effect of internal waves on the mixing process, Buoyancy Frequency (N) and Gradient Richardson Number (Rig) profiles were analyzed for different conditions, such as, two- and three layer fluid system, supercritical and subcritical flow conditions. It was observed that mixing in the water column induced by internal wave was more extended in a two layer fluid system than in a three layer fluid system. By analysing the Gradient Richardson Number at wave crests for both sub- and supercritical flow conditions, it was found that internal wave locked with density current head caused more shear instability and mixing in the water column relative to the wave which was separated from the current head. (Abstract shortened by UMI.)...