Re-entry body drag: shock tunnel experiments and computational fluid dynamics calculations compared

The best approach for conducting the research necessary for developing hypersonic flight vehicles is a close coupling between experiments that employ rapid measurement techniques and computational fluid dynamics (CFD) that appropriately accounts for the freestream nonuniformities, as well as for hypervelocity flow phenomena. This approach has been employed here, where stress wave force measurements and CFD calculations have been combined in an investigation of the axial drag on a generic re-entry body. Experiments were performed in argon and nitrogen, with test flows ranging in total enthalpy between 3 MJ/kg and 12 MJ/kg and Mach numbers varying from 6 to 13. The associated measured drag forces ranged from 300 to 360 N. For Mach 12 argon flows, the CFD overpredicted the drag by 8%, while for two hypervelocity nitrogen flows the CFD overpredicted the drag by at most 5%. Considering uncertainties in the force measurements and the CFD boundary conditions, the agreement is good, and the work highlights both the ability of the force measurement technique to respond to rapid changes in flow conditions and the importance of carefully accounting for flow gradients in the CFD boundary conditions. This paper was based on work that was presented at the 3rd International Symposium on Interdisciplinary Shock Wave Research, Canberra, Australia, March 1–3, 2006.