The Role of Erosion at the Head of Suspension Currents: Theory and Experiment

We study gravity-driven suspension currents sustained by continuous sediment erosion at the head. In this regime, basal erosion behaves as a narrow, steady supply of higher-density fluid into the current’s front. We suggest a possible bed induced erosion mechanism which delivers particles to the front. We investigate the head of such erosive suspension currents with laboratory experiments, theory and numerical simulations. We establish how the characteristic shape of the current’s head changes with the difference in fluid density between the ambient fluid and the material within the suspension front. The theory involves a density perturbation to the underlying potential flow. The simulations, based on FLUENT, examines details of the flow and informs assumptions of the theory. Suspension currents are imaged by use of fluorescent tracer in a water flume.