Gravity currents in two-layer stratified media

An investigation of gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. Our theoretical discussion considers slumping, supercritical gravity currents, i.e.~those that generate an interfacial disturbance whose speed of propagation matches the front speed. In contrast to previous studies, we parameterize the amplitude of the interfacial disturbance; the accuracy of this approach is confirmed by comparison against experimental and numerical data. Measured front speeds show positive agreement with analogue model predictions, which remain strictly single-valued. The front speed is essentially independent of the interfacial thickness, $\delta$, even in the limiting case where $\delta=H$ so that the environment is comprised of a uniformly stratified ambient with no readily discernible upper or lower ambient layer. Our experiments also consider the horizontal distance, $X$, at which the front begins to decelerate revealing a non-monotonic dependence on the ambient interface height.