In hypersonic low-density flows, slender vehicle dynamics are affected by various viscous flow phenomena. The true viscid-inviscid interaction is often difficult to extract from the background of support interference in wind tunnel tests and nonlinear six-degree-of-freedom motion effects in ballistic range tests, as was demonstrated by Welsh, Winchenbach, and Madagan several years ago. The range data and wind tunnel results for a 10-deg cone were shown to give completely different M^ trends for the pitch damping derivative. The aim of the present paper is to resolve this ambiguity and to help the vehicle designer decide how to obtain the best possible information about the full-scale vehicle dynamics using subscale dynamic test data.

Viscous Interaction or Support Interference-The Dynamicst's Dilemma

Static and dynamic pitching moment measurements were made on a family of constant volume elliptic cones about two fixed axes of oscillation in the NAE helium hypersonic wind tunnel at a Mach number of 11 and at Reynolds numbers based on model length of up to 14 million. Viscous effects on the stability derivatives were investigated by varying the Reynolds number for certain models by a factor as large as 10. The models investigated comprised a 7.75 deg circular cone, elliptic cones of axis ratios 3 and 6, and an elliptic cone with conical protuberances.

K. J. Orlik-Rueckermann

Papers

Static and dynamic pitching moment measurements on a family of elliptic cones at Mach number 11 in helium