Underwater High-Speed Gas Jet Flow Field and Noise Simulation Under Variable Pressure Gradient.

The study of underwater high-speed gas-fueled vehicle jet flow field and noise is crucial for underwater noise reduction and the design of future ultra-high-speed vehicles. However, due to complex interactions between incompressible fluid and high-pressure jet gas, the diffusion process exhibits phenomena like unstable gas-liquid mixing and complex wave structures inside the jet, posing challenges for flow field and noise simulation. This paper focuses on simulating the flow field structure and noise characteristics of high-speed gas-fueled vehicles during vertical ascent underwater at varying operating speeds. A two-dimensional axisymmetric numerical model is established using the Volume of Fluids (VOF) method, and simulations are conducted at operating speeds of 30m/s, 60m/s, and 90m/s, accounting for environmental pressure variations. The Large Eddy Simulation (LES) method is employed to obtain jet flow field characteristics, and the FW-H method is used to analyze jet noise characteristics. The research results indicate that as the operating speed increases, the pressure fluctuation range at the nozzle exit widens, and the velocity at the nozzle exit decreases. Regarding jet noise, the engine follows sound attenuation laws with distance and frequency even at high operating speeds. Furthermore, higher operating speeds result in elevated peak noise levels, while noise differences at different speeds become less apparent as the frequency rises.