An Experimental Investigation on High Frequency Laser Energy Deposition for Hypersonic Active Flow Control on a Flared Cone

Active flow control (AFC) is a promising technique for achieving rapid flow field manipulation in hypersonic conditions, addressing limitations associated with conventional control surface methods. A practical AFC approach involves high-frequency laser energy deposition into the flow through the ablation of a metallic surface. Laser ablation of this surface can generate a superheated gas plume with a localized low-density region. When applied to a hypersonic flow field, a transitory flow change can be executed to effectively alter the local high-speed flow parameters. This work applies the technique to a modified NASA 91-6 flared cone model to investigate its influence on the second mode instabilities and other observable indicators of boundary layer transition. Experiments were conducted in the Actively Controlled Expansion (ACE) hypersonic wind tunnel at the National Aerothermochemistry and Hypersonic Flight Laboratory (NAHL). A pulse-burst laser (PBL) system, housed within the Aerospace Laboratory for Lasers, Electromagnetics, and Optics (ALLEMO), varied the laser's repetition rate (RR) and energy output. The PBL system enabled testing of 3 laser RRs, each of which varied the output energies. Testing conditions included 4 different Mach numbers at a targeted unit Reynolds of 3 million. The study successfully captured hypersonic flow-field manipulation due to energy deposition, through observations of ablation-induced boundary layer instability amplification and other transitory indicators.