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Recent studies indicate that cavitation may play a vital role in laser lithotripsy. However, the underlying bubble dynamics and associated damage mechanisms are largely unknown. In this study, we use ultra-high-speed shadowgraph imaging, hydrophone measurements, three-dimensional passive cavitation mapping (3D-PCM), and phantom test to investigate the transient dynamics of vapor bubbles induced by a holmium:yttrium aluminum garnet laser and their correlation with solid damage. We vary the standoff distance ( SD) between the fiber tip and solid boundary under parallel fiber alignment and observe several distinctive features in bubble dynamics. First, long pulsed laser irradiation and solid boundary interaction create an elongated “pear-shaped” bubble that collapses asymmetrically and forms multiple jets in sequence. Second, unlike nanosecond laser-induced cavitation bubbles, jet impact on solid boundary generates negligible pressure transients and causes no direct damage. A non-circular toroidal bubble forms, particularly following the primary and secondary bubble collapses at SD = 1.0 and 3.0 mm, respectively. We observe three intensified bubble collapses with strong shock wave emissions: the intensified bubble collapse by shock wave, the ensuing reflected shock wave from the solid boundary, and self-intensified collapse of an inverted “triangle-shaped” or “horseshoe-shaped” bubble. Third, high-speed shadowgraph imaging and 3D-PCM confirm that the shock origins from the distinctive bubble collapse form either two discrete spots or a “smiling-face” shape. The spatial collapse pattern is consistent with the similar BegoStone surface damage, suggesting that the shockwave emissions during the intensified asymmetric collapse of the pear-shaped bubble are decisive for the solid damage.

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To obtain high specific work output with small mass flow rate, high-pressure ratios across the turbines are required in liquid rocket engine turbopumps. An impulse-type supersonic turbine can achieve this. To prevent losses due to low blade aspect ratio and issues related to manufacturing and industrial problems, partial admission configuration is adopted. Partial entry in a turbine is achieved by adjusting the extent of the nozzle arc of admission, leading to a strong unsteady circumferential asymmetry of flow parameters in the rotor passage, and degradation in efficiency. The pressing need of aerodynamic design of supersonic partial admission turbines to improve their efficiency demands an investigation of the viscous fluid dynamic of the turbine flow field. This work reports the aerothermodynamic steady state CFD analysis to obtain the performance parameters of a three-dimensional partial admission turbine for LOX booster turbopump in a semicryogenic engine using ANSYS® CFX. The areas of steady loss have been identified through entropy generation contours, and the effects associated with aerodynamic loss structures like secondary flow, shock location, recirculation with additional pumping and mixing losses have been investigated for designed operating condition corresponding to 100% nominal thrust.