Towards a universal criteria for turbulence suppression in dilute turbidity currents with non-cohesive sediments

Abstract

Turbidity currents exhibit fascinating physics as their sustained propagation depends on a tight interplay between the suspended sediments and turbulence. If resuspension dominates over deposition the intensity of the flow will increase, while if deposition dominates the flow turbulence can be completely damped inducing rapid settling of sediments and, eventually, flow extinction. This work explores the phenomenon whereby turbulence in a dilute turbidity current with non-cohesive sediments is abruptly extinguished owing to increasedsuspended sediment stratification. Three parameters control the flow dynamics: Reynolds number (Re_t), Richardson number (Ri_t) and sediment settling velocity (V_z). The condition for complete turbulence suppression can be expressed as a critical value for Ri_t V_z. Based on simulations, limited experiments and limited field data, the critical value appears to have a logarithmic dependence on Re_t.