High-resolution simulations of down-slope turbidity currents into a stratified saline ambient

We explore the properties of turbidity currents down a slope into a stratified saline ambient through highly resolved direct Navier-Stokes simulations, and compare our results to experimental results and analytical scaling arguments. Turbidity currents are buoyancy-driven flows where a denser fluid, charged with suspended particles, propagates through a lighter fluid under the effect of gravity. Three-dimensional simulations are conducted to investigate the properties and behaviour of these flows in various stratification and particle settling velocity configurations when they are moving down a slope. The unstable nature of the flow can be examined through three-dimensional representations of isosurfaces of constant particle concentration, as shown in figure 1. Figure 1: Downslope turbidity current as it destabilizes into a three-dimensional turbulent flow. The lobe and cleft instability plays a key role in the transition from two-dimensional KelvinHelmholtz instabilities to a fully developed three-dimensional turbulent flow. The instability is described in terms of wavelength and sensitivity to the Reynolds numbers. The adequate width of the domain is chosen accordingly. The front velocity is then computed for various configurations of stratification and particle settling velocity. The results are compared to experimental data and a simple scaling law, with very good agreement, confirming the ability of highly resolved numerical simulations to capture the physics of such flows. The particle settling behaviour is then discussed and the relation between the sedimentation rate and the settling velocity is monitored. Numerical simulations yield comprehensive information on the flow field and particle and salinity distribution. This is used to compute a time and space dependent entrainment velocity of the ambient into the