Observations of supersonic free shear layers

Abstract

Abstract. Visual spreading rates of turbulent shear layers with at least one stream supersonic were measured using Schlieren photography. The experiments were done at a variety of Mach number-gas combinations. The spreading rates are correlated with a compressibility-effect parameter called the convective Mach number. It is found that for. supersonic values of the convective Mach number, the spreading rate is about one quarter that of an incompressible layer at the same velocity and density ratio. The results are compared with other experimental and theoretical results.

Stability of Supersonic Flow with Injection

“…Two-dimensional free shear layers are a canonical flow in fluid mechanics. Information about the stability of free shear layers can be found in the literature [28][29][30][31][32][33], and in the review paper by Dimotakis [34]. A quantity called the vorticity thickness is the most common length scale used to nondimensionalize features in both compressible and incompressible shear layers.…”

Mixing Enhancement in a Scramjet Combustor Using Fuel Jet Injection Swirl.

“…x compressibility plays a significant role in the development of turbulent shear layers along with other factors like pressure gradient and heat released from chemical reactions. Since shear layer growth is related to large vortical structure development, compressibility effects on the shear layer growth can be analyzed within the reference frame of the motion of the vortical structures where u c is defined as the convective velocity [12], [13]. The relative convective Mach numbers for the two streams are…”

“…The constant 0.17 is an approximate value adjusted to the experimental results of Brown and Roshko (1974) with the observation that there is 20% or more error in determining the shear layer boundaries [13], [9]. The source of error is due to experimental inaccuracies and fundamental fluid dynamics that were not included in the analysis.…”

Framing Camera Improvements and hydrodynamic Experiments

“…It is related to compressibility effects in the shear layer, which have been shown to decrease the mixing-layer growth rate. Papamoschou and Roshko have shown experimentally a factor of 4 decrease in mixing-layer growth rate for M c = 1 compared to a subsonic flow [10]. These flows are typically observed far enough from the splitter plate that the flow has become fully turbulent.…”