Dynamic analysis of the interaction between unconfined turbidity currents and obstacles

Abstract

Sediment underflows, commonly known as turbidity currents, are a type of gravity current that occurs in deep oceans, lakes and river mouths. The present work studies the interaction of turbidity currents with different obstacles and substrates using the ultrasonic Doppler velocity profiler (UDVP) measurement technique in an unconfined basin with a lockbox. The following four conditions are tested: (a) flow of a turbidity current over a smooth surface, (b) flow over a smooth surface with an obstacle present, (c) flow over a rough surface and (d) flow over a rough surface with an obstacle present. It is observed that a rough surface significantly reduces current velocities and diminishes the presence of Kelvin-Helmholtz billows. The presence of a square-cylinder obstacle causes local regions of increased and decreased velocity, but does not have an effect on the global current velocity. Turbulence intensities are slightly higher than presented in previous confined studies.