A study of gravity currents carrying polydisperse particles along a V-shaped valley

Abstract

In this paper, we present a study of four full-depth high-Reynolds-number lock–release gravity currents carrying polydisperse particles along a V-shaped valley. The currents carried either irregular Silicon Carbide (SiC) or spherical Glass Beads (GBs), or a mixture of both. The initial particle size dispersals are shown to be well represented by histograms constructed with 20 size classes and vary between a plateau, a single-peaked, a skewed and a bimodal distribution. The experimental along-deposit particle size distributions were as well described using 20 size classes. The speed of the currents, the mass deposited, the material density of the deposit were also measured. The four experimental currents were modelled using a box model, in which we varied the number of particle size classes. Remarkably, the box model gives very good agreement with the experiments before the flow becomes viscous once at least 10 particle size classes are considered. In addition, we show that both the mass-weighted mean size of the initial distributions and the initial mass-weighted mean settling velocity can satisfactorily approximate the behaviour of the suspensions, apart from the runout length. Determining the latter requires that the models include a sufficient number of size classes (20 in this study).