The structure of a supersonic turbulent boundary layer subjected to concave surface curvature

Abstract

This paper reports an experimental investigation of the instantaneous structure of a supersonic turbulent boundary layer (M= 2.86,Reθ= 82000) over a short region of longitudinal concave surface curvature. The radius of curvature was 12 initial boundary-layer thicknesses and the turning angle was 16°. Severe distortion of the boundary layer occurred, as evidenced by an alteration of the mean velocity profiles and an increase in wall shear stress of 125%. The large-scale organized motions in the boundary layer were significantly altered as illustrated by changes in the character of the mass flux ‘fronts’ (large gradients in the fluctuating streamwise mass flux).

Scaling of heat transfer augmentation due to mechanical distortions in hypervelocity boundary layers

“…Experiments by Donovan 20 in a Mach 2.9 turbulent flow showed the absolute wall shear stress increased by about 125% and the skin friction by about 77% over a concave wall. When compared to a previous study 21 of a flat plate boundary layer with the same pressure gradient imposed, the turbulence levels and skin friction were amplified by an additional 60%-70% due to the curvature.…”

Effect of Concave Wall Geometry on Heat Transfer in Hypersonic Boundary Layers

“…Four model geometries were investigated: a flat plate, a linear ramp, a curved ramp with 25 degree turning angle (denoted Curved25), and a ramp with a 16 degree turning angle section (denoted Curved16) which was selected to match the experiments of Donovan et al . 10 Baseline measurements over the flat plate model showed experimental heat transfer distributions were in reasonable agreement with theoretical prediction. Measurements over the two models with concave surface curvature showed significant increase in heat flux with increasing streamwise distance over flat plate values.…”

“…The adverse pressure gradient created from wall curvature was observed to cause a 125% increase in wall shear stress, a result which is opposite that in a subsonic flow. 10 Significant effects on the turbulent structures were also detected in the presence of concave wall curvature; structure angles increased and the streamwise extent of the average large-scale motion nearly doubled.…”

“…Donovan et al 10 investigated the response of a supersonic (Mach 2.86), turbulent boundary layer to a segment of curved surface. The combination of the concave geometry, adverse pressure gradient, and bulk compression was found to increase the Reynolds stresses over similar flat plate models which were subjected to adverse pressure gradients only.…”

Influence of Surface Roughness on the Second Order Transport of Turbulence in Non-Equilibrium Boundary Layers

“…Collectively, the available turbulence data [Donovan (1993), Smith and Smits (1991), Jarayam et al (1987), Dussauge and Gaviglio (1987) and Thomann (1968)] indicate that the axial turbulence intensities decrease by 70-90% for I, and 10 values r (-0.4,-1.0) and (-0.1,-0.3), respectively. Because of the reduction in the fluctuating 13 properties, as well as reductions in the skin friction and heat transfer, favorable pressure gradients are often characterized as having a stabilizing effect.…”