Shock-Wave Mitigation Through Off-Body Pulsed Energy Deposition

A model of dynamic shock interaction predicts that pulsed energy addition upstream of a bow shock can be used to weaken the time-averaged shock strength. To explore these shock interactions, tests have been conducted in a small-scale, blowdown facility with off-body energy addition upstream of an oblique shock wave that was generated by a wedge in a Mach 2.4 flow. The off-body energy addition was simulated by laser-induced breakdown (350 mJ/pulse with 10-ns pulse duration). The dynamics of the interactions were captured in both schlieren and shadowgraph images taken at 250,000 and 500,000 frames per second and compared with the computational model. As expected, the laser-induced thermal spot weakened the oblique shock. The images also show the dynamics of the interaction between the shock waves generated by the laser breakdown in the flow and the oblique shock, including reflections off the wedge body. The results from the near-field experiments give insight into approaches that can be used to optimize the energy addition for practical applications, including sonic boom reduction.