Three-dimensional simulations of large eddies in the compressible mixing layer
Three-dimensional simulations of large eddies in the compressible mixing layer
The effect of Mach number on the evolution of instabilities in the compressible mixing layer is investigated. The full time-dependent compressible Navier–Stokes equations are solved numerically for a temporally evolving mixing layer using a mixed spectral and high-order finite difference method. The convective Mach number Mc (the ratio of the velocity difference to the sum of the free-stream sound speeds) is used as the compressibility parameter. Simulations with random initial conditions confirm the prediction of linear stability theory that at high Mach numbers (Mc > 0.6) oblique waves grow more rapidly than two-dimensional waves. Simulations are then presented of the nonlinear temporal evolution of the most rapidly amplified linear instability waves. A change in the developed large-scale structure is observed as the Mach number is increased, with vortical regions oriented in a more oblique manner at the higher Mach numbers. At convective Mach numbers above unity the two-dimensional instability is found to have little effect on the flow development, which is dominated by the oblique instability waves. The nonlinear structure which develops from a pair of equal and opposite oblique instability waves is found to resemble a pair of inclined A-vortices which are staggered in the streamwise direction. A fully nonlinear computation with a random initial condition shows the development of large-scale structure similar to the simulations with forcing. It is concluded that there are strong compressibility effects on the structure of the mixing layer and that highly three-dimensional structures develop from the primary inflexional instability of the flow at high Mach numbers
133-158
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Reynolds, W.C.
88dbc442-722d-424c-ac5b-cbd69bd5dacc
1991
Sandham, N.D.
0024d8cd-c788-4811-a470-57934fbdcf97
Reynolds, W.C.
88dbc442-722d-424c-ac5b-cbd69bd5dacc
Sandham, N.D. and Reynolds, W.C.
(1991)
Three-dimensional simulations of large eddies in the compressible mixing layer.
Journal of Fluid Mechanics, 224, .
(doi:10.1017/S0022112091001684).
Abstract
The effect of Mach number on the evolution of instabilities in the compressible mixing layer is investigated. The full time-dependent compressible Navier–Stokes equations are solved numerically for a temporally evolving mixing layer using a mixed spectral and high-order finite difference method. The convective Mach number Mc (the ratio of the velocity difference to the sum of the free-stream sound speeds) is used as the compressibility parameter. Simulations with random initial conditions confirm the prediction of linear stability theory that at high Mach numbers (Mc > 0.6) oblique waves grow more rapidly than two-dimensional waves. Simulations are then presented of the nonlinear temporal evolution of the most rapidly amplified linear instability waves. A change in the developed large-scale structure is observed as the Mach number is increased, with vortical regions oriented in a more oblique manner at the higher Mach numbers. At convective Mach numbers above unity the two-dimensional instability is found to have little effect on the flow development, which is dominated by the oblique instability waves. The nonlinear structure which develops from a pair of equal and opposite oblique instability waves is found to resemble a pair of inclined A-vortices which are staggered in the streamwise direction. A fully nonlinear computation with a random initial condition shows the development of large-scale structure similar to the simulations with forcing. It is concluded that there are strong compressibility effects on the structure of the mixing layer and that highly three-dimensional structures develop from the primary inflexional instability of the flow at high Mach numbers
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Published date: 1991
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Local EPrints ID: 72047
URI: http://eprints.soton.ac.uk/id/eprint/72047
ISSN: 0022-1120
PURE UUID: bfe42323-bd1c-4c7b-9ff0-12612ce85038
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Date deposited: 18 Jan 2010
Last modified: 14 Mar 2024 02:42
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Author:
N.D. Sandham
Author:
W.C. Reynolds
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