05/10/17 - Eletta Negretti
Gravity currents often occur on complex topographies and are therefore subject to spatial development. We present experimental results on continuously supplied gravity currents which are subject to sudden and/or gradually changing topography. We show that the overall gravity current characteristics such as the speed, the depth and the related bottom and interfacial drag strongly depend not only on the local Richardson number, but also on the local acceleration of the flow. It is shown that depending on an overall acceleration parameter, the current may undergo cycles of acceleration and deceleration if the bottom and interfacial drag are high enough to slow down the current rapidly, or may exhibit a monotonic increase of speed to a nearly constant velocity, depending on the initial conditions of the flow. From a time analysis of the velocity data we observe that even if the flow is stationary, some characteristics such as the location of initial onset of the shear instability evolve.