Two-Dimensional Large-Eddy Simulation of Density-Current Flow Propagating up a Slope

Abstract

A constant flow density current flowing on an inverse slope incline in the range of 1–6% slope is investigated using two-dimensional (2D) large-eddy simulations (LES). The dynamic Smagorinsky subgrid-scale model is used to improve the mixing accuracy of the flow field. The results of the simulation show that, as the inverse slope of the incline surface increases, the mixing in the body of the dense fluid with the ambient fluid increases at the beginning of the slope because of vortices generated by the flow reversal, whereas the mixing in the head of the density current generally decreases. As a result, the entrainment velocity along the free surface decreases by an increasing slope. As the inverse slope of the incline surface increases, the head thickness of the density current is depressed and departed from the body of the density current flow for the higher slopes (4 and 6% slopes). The entrainment result of a 2D large-eddy simulation is compared with 3D simulation to verify the suitability of 2D large-eddy simulation method, and it is shown that the 2D simulation can model the flow field of upslope flow with reasonable accuracy. The numerical simulations are further validated by comparing these numerical results with experimental data for the downslope density current flow and entrainment results of lock-exchange dense current propagating upslope.