The influence of large scale regular roughness on a Mach 5 turbulent boundarylayer and a compression corner was investigated on axisymmetric wind tunnelmodels. Three types of roughness were examined; a series of square cavities attwo different sizes and a 45 degree sawtooth. Typical sizes ranged from 50% to100% of an undisturbed boundary layer thickness. The roughness was limited toa short region followed by a smooth surface. Compression corners were formedby 15° and 20° flares located downstream of the roughness. The flow in the windtunnel was investigated in detail to obtain knowledge on operating conditions andflow quality. Liquid crystal thermography was developed for routine use inhypersonic blow-down wind tunnels with superior spatial resolution andexperimental uncertainties in the range of traditional techniques.The effect on flow parameters downstream of the last roughness element were 7,found to differ significantly for the different quantities. Velocity profiles were found i,to be less full and skin friction was found to be reduced for all streamwise "~distances. Surface heat transfer was increased in a short region limited to 1.5boundary layer thicknesses behind the roughness whereas surface pressure wasnot affected. Sawtooth shaped roughness was found to cause a stronger jdisturbance than square cavities of twice the size. Little influence of theroughness was noted on the flow over the compression corner. The flow over the20° compression corner showed an increase in upstream influence for thesawtooth shaped roughness as well as the larger cavities. Surface pressuremeasurements did not indicate a separation in any case. Heat transfermeasurements revealed a peak located approximately 0.25 boundary layerthicknesses behind the corner. No such feature was found in the surfacepressure distributions. It is suggested that a small scale separation is located veryclose to the corner causing the peak in heat transfer at reattachment without anyeffect on surface pressures. The existence of such a separation has beenconfirmed by surface flow visualisations for both flares.
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