LASER INTERFEROMETER SKIN-FRICTION MEASUREMENTS OF CROSSING-SHOCK-WAVE TURBULENT-BOUNDARY-LAYER INTERACTIONS

Wall shear stress measurements beneath crossing-shock-wave/turbulent b oundary-layer interactions have been made for three interactions of di fferent strengths. The interactions are generated by two sharp fins at symmetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 deg at Mach 3 and 15 deg at Mach 3.85. The measurements were made using a laser interferom eter skin-friction meter, a device that determines the wall shear by o ptically measuring the time rate of thinning of an oil film placed on the test model surface. Results of the measurements reveal high skin-f riction coefficients in the vicinity of the fin/plate junction and the presence of quasi-two-dimensional flow separation on the interaction centerline. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k-epsilon model, are co mpared with the experimental results for the Mach 3.85, 15-deg interac tion case. Although the k-epsilon model did a reasonable job of predic ting the overall trend in portions of the skin-friction distribution, neither computation fully captured the physics of the near-surface now in this complex interaction.