Two dimensional jet mixing of supersonic flow
Two-dimensional supersonic jet flows of air have been investigated by optical methods. The density distributions on the boundary of the jets under full expansion, over pressure and under pressure conditions at various Mach numbers were measured by an interferometer. The density distributions are of the form of error functions. For the full expansion and the over pressure cases, there is no interaction between the boundary layer flow and the flow in the core of the jet. The divergence of the jet mixing region decreases with increase of Mach number. For the under pressure case, there is interaction between the boundary layer and the shock. The shock is curved and the flow field behind the shock is non-uniform.
At low Mach number, the increase of Mach number has a destabilizing effect on the antisymmetric disturbances in the two-dimensional jet. When the Mach number on the boundary of the jet M̄ is high enough (about 1.70 or higher), the anti-symmetrical disturbance has been amplified to such a large extent that a steady flow of the jet cannot be obtained. But if the mean Mach number M̄ is above a critical Mach number (about 2.30), the anti-symmetrical disturbances disappear. This fact may be regarded as experimental evidence confirming the theoretical prediction that the two-dimensional laminar jet tends to be stable with respect to small disturbances at high Mach numbers.
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