Note on Unsteady Boundary-Layer Separation

Abstract

turbulent. It was assumed that in this case, the aft microphone gave a more realistic representation of the acoustic environment. In addition, it was assumed that the disturbance function Z was comprised solelv of acoustic disturbances. A plot of transition data obtained in the AEDC 16T as a function of acoustic level is shown in Fig. 3. The theoretical line was calculated for a Mach number of 0.8. Since the range of Mach numbers is small (0.3-1.6) and since the effect of Mach number is small for this range, this line represents a mean prediction line. Figures 2 and 3 indicate that transition can be predicted to within 10% with reasonable consistency. Additional factors having a significant effect on the data which are not included in the model and/or whose effect could not be removed from the data are: 1) pitch and yaw misalignment; and 2) acoustic levels due to proximity of transition to microphone location. The present technique has been applied to the low subsonic and supersonic flow regimes for the data of Refs. 4-6 and of 12 and 13. The preliminary results indicate that an extension to these flow regimes is feasible.