Roughness effects on gravity currents dynamics

The aim of this paper is the investigation of gravity currents moving on both smooth and rough beds by laboratory experiments. Gravity currents were produced by lock exchange release experiments. Three runs were performed in which the initial density of the gravity current was fixed, while three different bed’s roughness were tested. All the experiments were recorded by a camera and an image analysis technique was applied to measure the space-time evolution of the gravity current’s profile. For the experiment with a smooth bed three different phases can be observed in the gravity current’s dynamics: a first slumping or constant speed phase, a second self similar phase and a third viscous phase, in which the front velocity decreases as time increases. In both the experiments performed with a rough bed the measured front velocities were observed to be lower than the front velocity of the gravity current moving on a smooth bed. The observed general trend is that as the roughness increases the front speed decreases.