Experimental Analysis of the Turbulent Shear Stresses for Distorted Supersonic Boundary Layers
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1997, American Institute of Aeronautics and Astronautics, Inc. An experimental analysis of the turbulent shear stresses for a supersonic boundary layer distorted by streamline curvature induced pressure gradients was performed using laser Doppler velociruetry. Four pressure gradient flows were examined; a nominally zero pressure gradient case (M = 2.8, Ree = 11, 000, = 0.02); a favorable pressure gradient (M = 2.9, Ree = 15, 000, = -0.5); an adverse pressure gradient (M = 2.7, Ree = 12, 000, = 0.9), and a successive pressure gradient (M = 2.5, Ree = 12, 000, = -1.0 following a region of = 0.9). For the favorable pressure gradient, the turbulent shear stress levels across the boundary layer decreased by 70-100% as compared to the zero pressure gradient boundary layer. For the adverse pressure gradient, a 70-100% increase was observed. For the combined pressure gradient, the shear stresses returned to values similar to the zero pressure gradient flow. A new pressure gradient parameter was found to correlate well with the peak shear stress amplification. It was also postulated that the shear stress amplifications were in part the result of the non-uniform bulk dilatation/compression and streamline divergence/convergence implying a forcing phenomena that influenced the statistical uv correlation. The combined pressure gradient flow demonstrated that the turbulent structure adjusts relatively rapidly to the distortion. Numerical simulations of the mean velocity obtained with a k-(D turbulence model were found to agree very well with the present data. With the exception of the zero pressure gradient flow, the magnitude of the turbulent shear stresses were not accurately reproduced; however, the correct trends and profile shapes were predicted.