Single pulse laser energy deposition in quiescent air and hypersonic flows

Yang, L., Erdem, E., Zare-Behtash, H. and Kontis, K. (2012) Single pulse laser energy deposition in quiescent air and hypersonic flows. In 18th AIAA/3AF International Space Planes and Hypersonic Systems and Technologies Conference 2012. American Institute of Aeronautics and Astronautics. pp. 735-752 .

Abstract

Single laser energy deposition was experimentally investigated in both quiescent air and hypersonic flow. The induced flow pattern and the resulted perturbation to the hypersonic flow are observed using high-speed schlieren photograpay. A laser induced plasma was obtained by focusing a Q-switched single pulse Nd:YAG laser (wavelength 532 nm) with maximum laser energy of 203 mJ per pulse using a combination of concave-convex lenses. Initially, single pulse laser energy deposition was conducted in quiescent air at 101 kPa. Then, the laser beam was focused upstream of a truncated cone model as well as in the boundary layer above a flat plate in Mach 5 flow. In the quiescent air, the speed of the induced shock wave decays rapidly with time and the strength of the shock wave is weakened as it propagates outward. In the presence of hypersonic flow, the induced shock wave propagates downstream and interacts with the bow shock wave in front of the truncated cone. The bow shock wave is significantly mitigated with an effecting time of 450 μs after the laser pulse. Over the flat plate, the induced shock wave perturbs the boundary layer and causes separation in the adjacent upstream. A separation shock wave is formed due to the existence of a separation region. The entire structures are similar to that flow pattern induced by pulse micro-jet. The propagation of the induced shock wave changes the local pressure distribution and a stronger pressure disturbance is found in the downstream compared to than the upstream of the focal point. © 2012 by L. Yang, E.Erdem, H. Zare-Behtash and K.Kontis.

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Contributors

Author: H. Zare-Behtash

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