Influence of Regular Surface Waves on the Propagation of Gravity Currents: Experimental and Numerical Modeling (original) (raw)

The propagation of gravity currents is analyzed in the presence of regular surface waves, both experimentally and numerically, by using a full-depth lock-exchange configuration. Fulldepth lock-exchange releases have been reproduced in a wave flume, both in the absence and in the presence of regular waves, considering two fluids having densities ρ 0 and ρ 1 , with ρ 0 < ρ 1. Boussinesq gravity currents have been considered here (ρ 0 /ρ 1 ∼ 1), with values of the reduced gravity g in the range 0.01 ÷ 0.1 m/s 2 , while monochromatic waves have been generated in intermediate water depth. The experimental results show that the hydrodynamics of the density current is significantly affected by the presence of the wave motion. In particular, the front shows a pulsating behavior, the shape of the front itself is less steep than in the absence of waves, while turbulence at the interface between the two fluids is damped out. In the present test conditions, the average velocity of the advancing front may be decreased in the presence of the combined flow, as a function of the relative importance of buoyancy compared to wave-induced Stokes-drift. Moreover, a new numerical model is proposed, aiming at obtaining a simple, efficient and accurate tool to simulate the combined motion of gravity currents and surface waves. The model is derived by assuming that surface waves are not affected by gravity current propagation at leading order and that the total velocity field is the sum of velocities forced by the orbital motion and those