Similarity of gravity current fronts

Mixing processes in gravity current fronts have only recently been quantified due to their complex, unsteady nature. The similarity of the mixing processes in these pioneer works, however, has not been explored adequately. Experiments that explore a wide range of fronts have been performed. These experiments have used techniques that exhaustively sample the temporal (using a high-speed conductivity probe) and spatial (using planar laser-induced fluorescence) density field more thoroughly than any previous work. Both types of experiments have confirmed earlier research suggesting that low Reynolds number fronts mix differently and less than higher Reynolds number flows. Similarity appeared to be achieved for Re_q>1000, where Re_q is a Reynolds number based upon the cube root of the buoyancy flux into the front and the height of current. It appears that certain secondary mixing processes, seen by other researchers studying stratified mixed layers, are responsible for the earlier changes seen with Reynolds number and cause significant mixing at the front.