SIMILARITY OF GRAVITY CURRENT FRONTS

Mixing processes in gravity current fronts have only recently been qua ntified due to their complex, unsteady nature. The similarity of the m ixing 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 s ample the temporal (using a high-speed conductivity probe) and spatial (using planar laser-induced fluorescence) density field more thorough ly than any previous work. Both types of experiments have confirmed ea rlier research suggesting that low Reynolds number fronts mix differen tly 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 c urrent. It appears that certain secondary mixing processes, seen by ot her researchers studying stratified mixed layers, are responsible for the earlier changes seen with Reynolds number and cause significant mi xing at the front. (C) 1998 American Institute of Physics. [S1070-6631 (98)01812-1].