Experimental Investigation on Cavitation Dynamics during Water-Exit of Trans-Media Vehicle

The mechanical characteristics of cavitation collapse during the water-exiting process of trans-media vehicles critically influence structural integrity and operational safety. This study employs an integrated experimental approach using a multifunctional decompression water tank device coupled with high-speed imaging and a multi-parameter synchronous measurement system to investigate the dynamic behavior of cavitation collapse during underwater vehicle launch. We systematically reveal the evolution of the flow field, vehicle motion characteristics, pressure fluctuations, and underlying dynamic mechanisms throughout the collapse process. Experimental results demonstrate that cavitation collapse evolves through six distinct phases: Head contact, Progressive collapse, Synchronous collapse, Jet rebound, Secondary collapse, and Cascade collapse. The collapse process is governed by two principal pressure mechanisms: shock waves from liquid layers adhering to the vehicle surface during water-air interface crossing and pressure pulses from instantaneous gas compression. Axial propagation of collapse-induced pressure waves exhibits exponential attenuation in peak pressure, with the core collapse region concentrated below O.214L. Spatial analysis of pressure fields reveals significant localization of high-frequency signals and long-range persistence of low-frequency components, reflecting both local dynamics and global volume oscillations. Crucially, peak pressure intensity increases markedly with decreasing cavitation numbers, where low-cavitation conditions trigger high-frequency oscillations and asymmetric collapse behavior. These findings provide a quantified model for collapse energy dissipation and establish a foundation for predicting hydrodynamic loads during trans-media operations.