Compressibility effects on the structure of supersonic mixing layers: experimental results

An experiment in a supersonic mixing layer at convective Mach number Mc = 0.62 was performed to study the evolution of a flow from a turbulent boundary layer to a fully developed mixing layer. Turbulence measurements were taken and are interpreted with a diffusion model, which is well adapted to these flows. These measurements show that the level of turbulent friction varies with Mc proportionally to the spread rate. Our measurements appear to be consistent with the spreading rate of the layer and suggest that compressibility does not significantly alter the diffusion scheme at Mc = 0.62. This is also confirmed by a review of the existing data. Moreover, in the present flow, the anisotropy of the turbulent stresses seems to be affected by compressibility. The evolution of the radiated noise shows an increase corresponding to the developed part of the layer. Quantitative assessments of compressibility effects on turbulent quantities are given and are related to modifications in the structure of the flow.

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Density and Compressibility Effects on the Structure of Supersonic Mixing Layer

12th AIAA International Space Planes and Hypersonic Systems and Technologies ◽

10.2514/6.2003-6907 ◽

2003 ◽

Author(s):

Mohamed Menaa

Keyword(s):

Mixing Layer ◽

Supersonic Mixing ◽

Supersonic Mixing Layer ◽

Compressibility Effects

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Density and Compressibility Effects on the Structure of Supersonic Mixing Layer: Experimental Results and Similarity Analysis

Fluids Engineering ◽

10.1115/imece2003-42509 ◽

2003 ◽

Author(s):

M. Menaa ◽

J. P. Dussauge

Keyword(s):

Mach Number ◽

Velocity Profile ◽

Mixing Layer ◽

Variable Density ◽

Turbulent Shear ◽

Turbulent Friction ◽

Low Speed ◽

Rate Of Spread ◽

Supersonic Mixing ◽

Supersonic Mixing Layer

Self-similar solutions for mixing layers in supersonic flow and in subsonic flow with variable density are examined. The equation for the velocity profile is derived for a unity turbulent Prandtl number and/or prescribed density distributions. It is found that the shape of the velocity profile is not sensitive to Mach number and is nearly the same for supersonic layers with moderate convective Mach numbers and in low speed flows with variable density: in such conditions, the only compressibility effect is found on the rate of spread. It is also found that turbulent friction is a function of Mach number and of velocity and density ratios. The effect of these last parameters on turbulent friction in low speed layers is proposed. Finally the scaling for turbulent shear stress last parameters on turbulent friction in low speed layers is proposed. Finally the scaling for turbulent shear strees in supersonic mixing layer is discussed. A simple formulation is proposed, in which the effects of density ratio and convective Mach number can be sepearated, as it is usually done for the rate of spread.

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