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Transition stages of Rayleigh–Taylor instability between miscible fluids
Ist Teil von
Journal of fluid mechanics, 2001-09, Vol.443, p.69-99
Ort / Verlag
Cambridge, UK: Cambridge University Press
Erscheinungsjahr
2001
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Direct numerical simulations (DNS) are presented of three-dimensional, Rayleigh–Taylor
instability (RTI) between two incompressible, miscible fluids, with a 3:1
density ratio. Periodic boundary conditions are imposed in the horizontal directions
of a rectangular domain, with no-slip top and bottom walls. Solutions are obtained
for the Navier–Stokes equations, augmented by a species transport-diffusion equation,
with various initial perturbations. The DNS achieved outer-scale Reynolds numbers,
based on mixing-zone height and its rate of growth, in excess of 3000. Initial growth is
diffusive and independent of the initial perturbations. The onset of nonlinear growth
is not predicted by available linear-stability theory. Following the diffusive-growth
stage, growth rates are found to depend on the initial perturbations, up to the end of
the simulations. Mixing is found to be even more sensitive to initial conditions than
growth rates. Taylor microscales and Reynolds numbers are anisotropic throughout
the simulations. Improved collapse of many statistics is achieved if the height of the
mixing zone, rather than time, is used as the scaling or progress variable. Mixing has
dynamical consequences for this flow, since it is driven by the action of the imposed
acceleration field on local density differences.