Theoretical analysis of aero-optical effect in the two-dimensional large-scale structure of 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.

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An experimental investigation of a large-scale structure of a two-dimensional backward-facing step by using advanced multi-point LDV

Experiments in Fluids ◽

10.1007/s00348-003-0718-6 ◽

2004 ◽

Vol 36 (2) ◽

pp. 274-281 ◽

Cited By ~ 24

Author(s):

Noriyuki Furuichi ◽

Tadashi Hachiga ◽

Masaya Kumada

Keyword(s):

Experimental Investigation ◽

Large Scale ◽

Large Scale Structure ◽

Scale Structure ◽

Two Dimensional ◽

Backward Facing Step

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A Dynamical and Chemical Study of NGC 6302

Symposium - International Astronomical Union ◽

10.1017/s0074180900094080 ◽

1983 ◽

Vol 103 ◽

pp. 509-509

Author(s):

I.J. Danziger ◽

D. Baade ◽

P. D. Atherton ◽

K. Taylor ◽

A. Boksenberg

Keyword(s):

Radial Velocity ◽

Large Scale ◽

Flow Model ◽

Chemical Study ◽

Large Scale Structure ◽

Scale Structure ◽

Two Dimensional ◽

Cavity Model ◽

Ionic Concentrations ◽

The One

From five spectrograms obtained at five different positions in the nebula, relative ionic concentrations have been derived with respect to the nucleus. They show that the degree of excitation generally decreases with distance from the nucleus. But there are also areas with locally enhanced or attenuated excitation. Taurus data, a series of two-dimensional monochromatic images centered on (OIII) λ 5007, have been used to construct a two-dimensional velocity map. It shows a large-scale structure similar to the one of direct images with the biconical pattern being at least partly present. Areas of locally lower radial velocity which seem to be inversion symmetrically distributed with respect to the centre, are also distinguished. They do not have pronounced counterparts on direct images. The cavity model suggested by Barral et al. (1982, MNRAS 199, 95) for NGC 6302 and Icke's biconical flow model (1981, Ap. J. 247, 152) are discussed.

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