Numerical study of turbidity currents with sudden-release and sustained-inflow mechanisms

A well-tested numerical model based on the Reynolds averaged Navier-Stokes equations with k-epsilon turbulence closure is further validated against three groups of experimental data on lock-exchange gravity flows. The model is then applied to study larger-scale turbidity currents with sudden-release and/or sustained inflow mechanisms. At the field-scale, sudden-release turbidity currents are found to be essentially unsteady with depth-averaged flow variables varying with time and distance from the upstream boundary. Turbidity currents with sustained inflows reach a quasi-equilibrium state in the body of the current. The simulation of a turbidity current initiated by sudden-release and then fed by sustained inflow reveals that, initially, two bore heads appear in the current with the second bore head resulting from sustained inflow and eventually catches up with the first one. Model results show that, depending on onset mechanism and slope, if the erosion rate of sediment exceeds the deposition rate, turbidity currents at the field scale can experience self-acceleration, a process predicted earlier by theory but not demonstrated in laboratory experiments.