Development of gravity currents on slopes under different interfacial instability conditions

International audienceWe present experimental results on the development of gravity currents moving onto sloping boundaries with slope angles $θ = 7°$, $10°$ and $15°$. Different regimes of flow development are observed depending on the slope angle and on the initial velocity and density profiles, characterized by the Richardson number $J_i = δ_i g_0′/\Delta u_i^2$, where $δ_ i$ , $u _i$ and $g′_0$ are, respectively, the velocity interface thickness, the maximum velocity difference and reduced gravity at the beginning of the slope. For $J_ i > 0.7$ and the larger slope angle, the flow strongly accelerates, reaches a maximum at the beginning of the Kelvin-Helmholtz instability, then decelerates and re-accelerates again. For $0.3 0.3$ predict that the current requires a distance of at least $x_ n ≈ 40h_ i$ to reach a normal state of constant velocity, which is much larger than the distance $x _n ≈ 10h_ i$ required in the case of a current with $J_ i\leq 0.3$ that is commonly assumed for downslope currents