Comment on "Flutter of Flat Finite Element Panels in a Supersonic Potential Flow"

Abstract

about Mach 3, cone angle and bluntness ratio are equally important; and above Mach 3, bluntness is the relatively stronger parameter in establishing the base pressure level. The validity of the correlation is demonstrated by comparison with specific 9 and 10 deg cone data for sharp and 0.3 bluntness ratio noses which are given in Fig. 4. Data for other cone angles and bluntness ratios exhibit an equally good agreement with the prediction as would be expected based on Fig. 2; however, all of these data are not given in Fig. 4 for clarity. Also, total drag measurements obtained in an aeroballistics range on sharp 10-deg semiangle cones during the course of the transition experiments reported in Ref. 4 were analyzed. A sting free, flight base pressure was extracted from these data by subtracting a calculated forebody drag (pressure and skin friction) from the measured total drag. This calculations can be made with great precision for the sharp slender cone in question since the location of transition was measured. The relatively precise free-flight base pressure results obtained in this manner are given in Fig. 4 and further confirm both the absence of sting effects and the validity of the correlation. Even at Mach numbers in excess of eight, base pressure predictions utilizing this technique are in good qualitative agreement with the available turbulent data for sharp or small bluntness cones (up to Mach ~ 20). Summary At supersonic speeds, the base drag of sharp or blunt conical bodies represents a significant fraction of the total