Transient behavior of overflowing gravity currents interacting with a roughness array

We present experimental measurements revealing the density and velocity structure of gravity currents flowing over closely spaced roughness elements. We focus on their transient response, extending beyond the steady-state analysis of earlier studies. Our observations demonstrate that while currents flow above the obstacle array, convective exchange at the current's underside cause dense fluid to drain into the obstacle array, significantly altering the current's structure and evolution. These findings provide new insights into the fundamental mechanics of gravity currents interacting with complex topography.