Temperatures were measured on the external surface of a straight hollow cylinder alined parallel to the air stream. The stream Mach num-ber was 3.12, the Reynolds number varied between 1x105 and 7H105 per inch, and there was negligible beat transfer between the cylinder and the stream. From the temperature measurements, it was possible to obtain laminar and turbulent recovery factors and transition locations for the cylinder with and without single roughness elements. The peak in the surface temperature was found to coincide with the mean location of the transition point as determined from schlleren observation. With no roughness element, the transition Reynolds number was found to vary approximately as the square root of the stream Reynolds number per inch. The data for the single roughness elements were correlated according to Dryden'e low-speed correlation parameter; however, the present results show that three to seven times the roughness intensity is necessary at Mach 3.12 to affect transition than is required at low subsonic speeds.
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