CORRELATIONS OF SUPERSONIC BOUNDARY-LAYER TRANSITION ON CONES INCLUDING EFFECTS OF LARGE AXIAL VARIATIONS IN WIND-TUNNEL NOISE.

Transition data on sharp-tip cones in two pilot low-disturbance wind tunnels at Mach numbers of 3. 5 and 5 have been correlated in terms of noise parameters with data from several conventional wind tunnels and with data from supersonic flight tests on the Arnold Engineering Development Center 10 degree transition cone. The noise parameters were developed to account for the large axial variations of the free-stream noise and the very-high-frequency noise spectra that occurred in the low-disturbance tunnels for some test conditions. These two pilot tunnels utilize some new and unique techniques to reduce the free-stream noise levels below those which are present in conventional tunnels. One of these techniques involves the use of boundary-layer suction slots upstream of the throat. By operating these tunnels with the suction off or on, the noise could be varied from high levels, approaching those in conventional tunnels, to extremely low levels.