Model Support Effects on Aerodynamic and Wake Characteristics of Large Angle Cones

Abstract

The Langley Research Center of NASA has conducted an experimental program on a 140° cone model in an attempt to gain more insight into such factors as Reynolds number effects and sting-support interference in wind-tunnel tests of decelerator-shaped vehicles. In addition, an effort was made to assess the cause of experimentally observed asymmetric wake patterns behind blunt bodies, often attributed to model and/or support asymetrics, by utilizing an existing tunnel-spanning support and a single wall-mounted support in tests with the same model. The tests were performed in the Langley Unitary Plan wind tunnel. The 140° cone force tests were performed at M = 1.50 and 2.00 through an angle-of-attack range from about —3° to 13° at Reynolds numbers from 1.74 x 10 to 1.44 x 15 based on model diameter, D. Sting support diameters varied from 0.125 d/D to 0.500 d\D. The wake survey tests behind a 120° cone were performed at a Mach number of 1.60, at angles-ofattack of 0° and 5°, and at a Reynolds number of 6.60 x 10. Additional force data on the 140° cone at M= 1.50 and 2.0 and wake survey data on the 120° cone at different x/D distance may be found in Ref. 1. The results of the force tests are presented in coefficient form about the body axis with the moment reference located at the model base. These coefficients are nondimensionalized with base area and base diameter of the cone. Base pressure tubes were located at the centroid of area on the base of the cone at 90° intervals and also in the balance cavity. Chamber and base pressures were measured on all sting-diameter configurations; however, the axial-force coefficients are for total values and have not been corrected for base pressure. In the wake survey measurements, two support systems were used with the 120° cone. One support system was mounted in such a manner as to span the tunnel test section. The second support system was a single-strut, mounted on the wall of the tunnel. The wake survey results are presented as the ratio of local dynamic pressure to that in freestream. Local pressures were measured by means of a multitube rake. The rake was mounted in a vertical position in the tunnel and could be moved laterally and longitudinally in the test section.