Frequency modulation in shock wave-boundary layer interaction by repetitive-pulse laser energy deposition

Modulation of shock foot oscillation due to energy deposition by repetitive laser pulses in shock wave-boundary layer interaction over an axisymmetric nose-cylinder-flare model in Mach 1.92 flow was experimentally studied. From a series of 256 schlieren images, density oscillation spectra at each pixel were obtained. When laser pulses of approximately 7 mJ were deposited with a repetition frequency, f(e), of 30 kHz or lower, the flare shock oscillation had a peak spectrum equivalent to the value of f(e). However, with f(e) of 40 kHz-60 kHz, it experienced frequency modulation down to lower than 20 kHz. (C) 2015 AIP Publishing LLC.