Research on the cavity flow and motion characteristics of vehicle launched underwater in waves

The underwater vertical launch of a vehicle involves a complex gas-liquid mixing process. Upon water exit, the large-scale collapse and shedding of attached cavitation generate high-frequency transient impact loads on the vehicle surface, significantly influencing its load distribution and motion trajectory. Under extreme sea conditions with wave activity, strong disturbances of the wave surface particles complicate the evolution and development of cavitation during water exit. This paper presents numerical simulations of a vehicle exiting water in a wave environment, focusing on the influence of wave phase on the evolution of the multiphase flow field and the motion characteristics of the vehicle. Results show that cavitation exhibits significant asymmetric evolution during water exit at the crest and trough. At the crest phase, the cavity size on the downstream side is considerably larger than that on the upstream side, while the opposite occurs at the trough phase. Simultaneously, the vehicle experiences a pair of lateral loads characterized by narrow pulse widths, substantial magnitude differences, and a noticeable time lag. The load on the side with larger cavitation is several times greater than on the opposite side. When exiting at the crest and trough phases, the vehicle's trajectory and deflection angle curves exhibit significant deviations, with opposite deflection directions between the two phases. In contrast, the motion characteristics at the pre-crest and post-crest phases are closer to those in calm water, with minimal deflection.