Author(s): James R. Hoyes; Derek B. Am; William D. Mccaffrey; Lionel Elliott; Jeff Peakall; Mohammed Pourkashanian
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Keywords: Gravity Current; Direct Numerical Simulation (DNS); Computational Fluid Dynamics (CFD)
Abstract: It is proposed that three-dimensional direct numerical simulation can be applied to investigate high Reynolds number lock-release gravity currents, provided the computational mesh employed in the simulation is fine enough to give adequate resolution of the thin density interface at the front of the flow. The thin density interface at the front of the flow is imperative to the observed self-similarity of gravity current propagation, which in turn is relied upon by the two well established approaches used to investigate their dynamics, namely, shallow water theory and experimentation. To test the proposal, three-dimensional direct numerical simulations were performed of a lock-release gravity current at Re 10. 1 410. Three-dimensional iso-surfaces of constant density produced from the direct numerical simulations exhibit all the characteristic features of a gravity current, including lobe and cleft instabilities at the front of the flow and Kelvin-Helmholtz type instabilities at the interface between light and dense fluids. The effects of mesh resolution are presented and it is shown that whilst the overall structure of the flow is not largely effected by the mesh resolution, the turbulent mixing within the flow is better resolved using a higher resolution mesh. Width-averaged density profiles from the simulation performed on the highest resolution mesh are presented and shown to be in excellent agreement with an experimentally-measured density profile. =T ×
Year: 2007