Author(s): Seng-Keat Ooi; George Constantinescu; Larry Weber
Linked Author(s): George Constantinescu, Larry J. Weber, Seng Keat Ooi
Keywords: Gravity Currents; Lock-Exchange Flows; Large Eddy Simulation
Abstract: Lock-exchange gravity current flows produced by instantaneous release of a heavy fluid are investigated using 2-D Large Eddy Simulation (LES). The model is first validated using the 2D Direct Numerical Simulation (DNS) results of Hartel et al. [1] for the classical lock- exchange gravity current flow in an infinite channel (no lateral walls) with no-slip walls. Then the code is applied to study quantitative and qualitative aspects of the evolution of gravity current flows for the case in which the heavier (lock) fluid is initially situated in between the vertical end wall on the left and the lock barrier and extends over the whole channel depth. All solid boundaries are simulated as no-slip walls. Three different length over depth aspect ratios of initial domain occupied by the heavier fluid are considered corresponding to the cases studied experimentally by Hacker et al. [2]. It is found that 2D LES is able to capture most of the physics observed in experiments including the evolution of the head and its velocity during the slumping phase, as well as the formation of coherent billow structures at the apex of the head due to Kelvin-Helmholtz instabilities. The simulations also allow investigating the evolution and structure of the gravity current during the transition between the slumping phase and the self-similar phase when the bore formed due to reflection at the end wall of the return flow overtakes the front. Our simulations also show that during the similarity phase the front position xf advances as t2/3 (t is the time measured from release) and the front speed decays as t-1/3 which is consistent with the theory.
Year: 2005