Experiments on two-layer stratified gravity currents in the slumping phase

Abstract

Experiments on gravity currents produced from full-depth two-layer stratified buoyancy sources propagating in the slumping phase are presented in the paper. The Froude number in the slumping phase, , where is the front velocity, is the average reduced gravity and H is the lock height, is influenced by the density difference ratio, , and the buoyancy distribution parameter, , where , and are the fluid densities in the upper layer, lower layer and ambient environment while and represent the buoyancies in the upper layer and lower layer. The flow morphology of two-layer stratified gravity currents in the slumping phase can be categorized into two different regimes, demarcated by . For , the gravity currents are dominated by the lower layer and the lower layer takes the lead throughout the slumping phase. The Froude number in the slumping phase for increases as decreases from unity. For , the gravity currents are dominated by the upper layer and the upper layer overrides and outruns the lower layer. The Froude number in the slumping phase for decreases as decreases from unity. As , the upper layer and lower layer propagate forward approximately at the same speed and the Froude number in the slumping phase maintains at irrespective of the density difference ratio. For weakly stratified two-layer buoyancy source, , the influence of the buoyancy distribution parameter diminishes and the Froude number in the slumping phase approaches .