Experimental downslope gravity currents over a synthetic topography

Abstract

Experimental lock-release gravity currents are investigated as they propagate downslope over varying synthetic topography. We emulate and investigate the dynamics of thermally driven winds that propagate downslope while interacting with the roughness of a complex topographic surface. The mixing processes between the gravity currents and their surroundings are studied with Particle Image Velocimetry (PIV), and entrainment is quantified. The magnitude of the entrainment coefficient is shown to increase as the roughness of the slope increases. Shadowgraph visualizations qualitatively reproduce this behavior. Finally, pressure fields are estimated from velocity fields, and pressure time series are obtained over synthetic stations along the topographic surface. The arrival of gravity currents is shown to be detected in the pressure time series. This last result may help detect atmospheric gravity currents using only surface pressure measurements.