Fin Leading-Edge Sweep Effect on Shock-Shock Interaction at Mach 6

Abstract

The effects of n leading-edge sweep on peak heating rates due to shock-shock interaction have been experimentally examined in the NASA Langley Research Center 20-Inch Mach 6 Tunnel. The shock interaction was produced by the intersection of a planar incident shock (16.8-deg shock angle relative to the freestream, generated by a 9-deg wedge) with the bow shock formed around a 0.5-in.-diam cylindrical leading-edge n. Heating distributions along the leading-edge stagnation line have been obtained using densely spaced thin-lm resistive-type sensors. Schlieren images were obtained to illustrate the very complex shock-shock interactions. The n leading-edgesweep angle was varied from 15 deg swept back (relative to the normal to the freestream) to 45 deg swept forward for a freestream unit Reynolds number of 2 £ 10 6 /ft. Two models were utilized during the study, one with 0.025-in. spacing between gauge centers, and the other with 0.015-in. spacing. Gauge spatial resolution on the order of 0.015 in. appeared to capture the narrow heating spike accurately. Peak heating due to shock interaction was maximized when the n was swept forward 15 and 25 deg, both promoting augmentationsover seven times the baseline value. The schlieren images for these cases revealed Type IV and Type III interactions, respectively. NomenclatureCh = nondimensional Stanton number, q=½ 1 u 1 .h t2 ¡ h 1 ) C h ref = reference Stanton number, measured for each run from undisturbed end of model h t2 = stagnation enthalpy behind normal shock, Btu/lbm h 1 = freestream enthalpy, Btu/lbm L = length of leading edge, 4 in. M 1 = freestream Mach number P t1= stagnation pressure, psi q = heat transfer rate, Btu/ft 2 ¢ s Re 1 /ft = freestream unit Reynolds number, ft ¡1 T t 1 = stagnation temperature, ± R T 1 = freestream temperature, ± R t = time, s u 1 = freestream velocity, ft/s x = distance measured from incident shock location, in. = incident shock angle relative to the freestream, deg ± = shock generator angle relative to the freestream, deģ = n sweep angle relative to the normal to the freestream (where positive is de ned as swept back and negative as swept forward), deg ½ 1 = freestream density, slug/ft 3

Global Aeroheating Measurements of Shock-Shock Interactions on a Swept Cylinder

“…This improved spatial resolution is significant because the heat transfer data from these line cuts display similar trends to equivalent cases in Ref. 11. Thus, the assertion in Ref.…”

“…Since the time of Edney's study, another sub-type has been added to the shock-shock interaction lexicon, the Type IVa interaction, in which the supersonic jet is present but largely misses the surface of the body. Berry and Nowak 11 experimentally investigated the effect of fin sweep angle on the increase in the peak heating on a leading edge or strut of a hypersonic vehicle due to different types of three-dimensional (3D) shock-shock interactions. This study included a systematic sweep of fin angles to capture most of the general classification types, as shown in the schlieren images in Fig.…”

“…Most of the wind tunnel runs in Ref. 11 were conducted at a unit Reynolds (Re ∞ ) number of 2.1×10 6 /ft with the SG at 9° to the flow. The results of Ref.…”

“…b) Photographic examplesof these shock types (including Type IVa, but excluding Type VI) from Test 6692 11. …”

Aerothermodynamic flight simulation capabilities for aerospace vehicles

“…Berry and Nowak, 1997). Thin-film gages were etched onto a flat polyimide film and the film wrapped and bonded to the cylindrical test article.…”