Characterizing Wake Roll-Up and Vortex Structure for Delta Wing Configuations Featuring Flow Control Devices at Low Reynolds Number

Various configurations of a cropped delta wing featuring a NACA 0012 wing-section were evaluated experimentally at a Reynolds number of 5.0 x 105 in the Air Force Institute of Technology Low-Speed Wind Tunnel facility. The effects of active flow control (AFC) and passive boundary-layer fences (BLF) were shown to improve high angle of attack delta wing performance. The AFC BLFs were shown to replicate the performance enhancements found in passive BLFs without incurring a drag penalty. An experimental characterization of the wake region is presented to compare the wake roll-up and leading edge vortices for these baseline, passive BLF, and AFC BLF delta wing configurations. Using a tuft mesh and a constant temperature anemometry triple wire probe, the wake was characterized at several discrete planes of interest aft of the trailing edge. This wake data was used to elucidate causes for AFC BLF configuration increasing the maximum lift coefficient by 60.3%. The present study shows this aerodynamic improvement is largely attributed to: 1) strengthening the leading edge vortex (LEV), which delays vortex breakdown, and 2) truncating spanwise flow

Numerical Simulation of Heat Transfer and Chemistry in the Wake Behind a Hypersonic Slender Body at Angle of Attack

The effect of thermal and chemical boundary conditions on the structure and chemical composition of the wake behind a 3D Mach 7 sphere-cone at an angle of attack of 5 degrees and an altitude of roughly 30,000 m is explored. A special emphasis is placed on determining the number density of chemical species which might lead to detection via the electromagnetic spectrum. The use of non-ablating cold-wall, adiabatic, and radiative equilibrium wall boundary conditions are used to simulate extremes in potential thermal protection system designs. Non-ablating, as well as an ablating boundary condition using the “steady-state ablation” assumption to compute a surface energy balance on the wall are used in order to determine the impacts of ablation on wake composition. On-body thermal boundary conditions downstream of an ablating nose are found to significantly affect wake temperature and composition, while the role of catalysis is found to change the composition only marginally except at very high temperatures on the cone’s surface for the flow regime considered. Ablation is found to drive the extensive production of detectable species otherwise unrelated to ablation, whereas if ablation is not present at all, air-species which would otherwise produce detectable spectra are minimal. Studies of afterbody cooling techniques, as well as shape, are recommended for further analysis