Hydroacoustic characteristics of single and multiple cryogenic bubble collapse near solid walls

The collapse of cryogenic cavitation bubbles near solid boundaries involves strong thermo-compressible effects that influence both wall loading and acoustic radiation. In this study, three-dimensional simulations based on the compressible multiphase Navier–Stokes equations coupled with a volume of fluid framework and the Ffowcs Williams–Hawkings acoustic analogy are performed to investigate hydrogen vapor bubble collapse near smooth and rough walls. The model incorporates phase transition and liquid compressibility via the Tait equation. The central physical question is whether cryogenic cavitation acoustics near walls are controlled primarily by boundary properties or by intrinsic bubble dynamics and bubble–bubble coupling. Validation against the thermal Rayleigh solution shows a maximum deviation of approximately 8%, and comparison with experimental data confirms the accuracy of the predicted wall pressure and acoustic fluctuations. These results show that surface roughness increases the first wall-pressure peak during early expansion, whereas its influence on jet-impact pressure and bubble volume evolution remains limited. Variations in contact angle do not significantly modify collapse dynamics or acoustic pressure. Despite local changes in near-wall flow structures, the acoustic response across the receiver array remains largely unaffected by surface roughness and wettability, indicating that acoustic radiation is primarily governed by intrinsic bubble dynamics. In contrast, multi-bubble configurations intensify wall-directed microjet velocity, wall pressure, and acoustic emission through bubble–bubble interaction and coherent superposition of collapse-generated pulses. These findings establish a physical separation between localized boundary effects and radiated acoustic response.