Particle flux through sediment fingers

Experiments were carried out to examine the fingering convection process occurring at the interface between a layer of warm, particle-laden water overlying a layer of cold, fresh water. In the formation stage, the rapidly descending fingers were irregular, with large caps or vortex rings at their tips. However, when fully developed, the sediment fingers were of approximately the same size, appearing in a regular array all along the interface. Contrary to the case of salt-finger convection, in which the downward diffusing component is thoroughly mixed in the upper layer at all times, the particle-laden fluid descends as an integral unit as convection proceeds, leaving behind a growing fluid region with a much-reduced particle concentration in the top part of the upper layer. The measured flux of SiC particles as a result of finger convection for a range of initial density ratios is much increased from that caused by sedimentation based on settling velocity when the relative density difference because of particle concentration is high. At low relative density differences, the particle flux is essentially due to settling.