Validation of a two-point spectral turbulence model for inhomogeneous flows

Implicit Large Eddy simulations (ILES) of an inhomogeneous variable density (VD) flow in the form of Rayleigh-Taylor (RT) turbulence is used to validate and calibrate a spectral turbulence model. The two-point, spectral model is built on the approach laid out in the BHRZ¹ method, and computes the time evolution of two-point correlations of the density fluctuations with the momentum and specific volume. For such flows, earlier efforts² have shown the central role played by the density-specific volume correlation b in the production of mass flux a, which in turn drives the conversion of buoyant potential energy into kinetic energy E. The time evolution of spectral distributions of a(k), b(k), and E(k), where k is the wavenumber, are predicted by the spectral closure model and compared with data from ILES. The RT system is initialized with a multimode perturbation at the interface between a light fluid accelerated into a heavier fluid against gravity. The simulations were performed using the MOBILE software³ at a resolution of 512 x 512 x 2048 zones.

¹D.C. Besnard, F. Harlow, R. Rauenzahn and C. Zemach, Theor. Comp. Dyn., 8, 1-35, (1996)

²D. Livescu and J.R. Ristorcelli, J. Fluid Mech., 591, 43-71, (2007)

³A.G.W. Lawrie and S.B. Dalziel, Phys. Fluids, 23, 085109 (2011)