High-resolution simulations of gravity and turbidity currents

Eckart Meiburg, Ph.D.
Professor and Chair
Dept. of Mechanical and Environmental Engineering
University of California, Santa Barbara

We will present an overview of high-resolution, Navier-Stokes based simulations of gravity and turbidity currents, with the focus being on the standard lock-exchange configuration. The turbidity currents considered are driven by particles that have negligible inertia and are much smaller than the smallest length scales of the buoyancy-induced fluid motion. The governing equations are integrated numerically with a high-order, mixed compact finite difference and spectral/spectral-element technique.

We will discuss differences between two- and three-dimensional gravity current dynamics, along with the influence of slip and no-slip walls. Flow features due to large, non-Boussinesq density differences will be analyzed, and differences in the dynamics of the light and heavy fronts will be discussed. In the analysis of turbidity currents, special emphasis is placed on the sedimentation and resuspension of the particles, and on their feedback on the flow. Resuspension is modeled as a diffusive flux of particles through the bottom boundary. Time-dependent sedimentation profiles at the channel floor are presented which agree closely with available experimental data. The conditions under which turbidity currents may become self-sustaining through particle entrainment are investigated as a function of slope angle, current and particle size, and particle concentration.