The propagation of gravity currents in a V-shaped triangular cross-section channel: experiments and theory

We investigate the motion of high-Reynolds-number gravity currents (GCs) in a
horizontal channel of V-shaped cross-section combining lock-exchange experiments and a theoretical model. While all previously published experiments in V-shaped channels were performed with the special configuration of the full-depth lock, we present the first part-depth experiment results. A fixed volume of saline, that was initially of length x0 and height h0 in a lock and embedded in water of height H0 in a long tank, was released from rest and the propagation was recorded over a distance of typically 30x0. In all of the tested cases the current displays a slumping stage of constant speed uN over a significant distance xS, followed by a self-similar stage up to the distance xV, where transition to the viscous regime occurs. The new data and insights of this study elucidate the influence of the height ratio H = H0/h0 and of the initial Reynolds number Re0 = (g 0h0) 1/2h0/ν, on the motion of the triangular GC; g 0 and ν are the reduced gravity and kinematic viscosity coefficient, respectively. We demonstrate that the speed of propagation uN scaled with (g 0h0) 1/2 increases with H, while xS decreases with H, and xV ∼ [Re0(h0/x0)] 4/9 . The initial propagation in the triangle is 50 % more rapid than in a standard flat-bottom channel under similar conditions. Comparisons with theoretical predictions show good qualitative agreements and fair quantitative agreement; the major discrepancy is an overpredicted uN, similar to that observed in the standard flat bottom case.