Integrated analysis of flow-induced noise from submarine under snorkel condition

Abstract

Accurate evaluation of the underwater radiated noise under the snorkel operating condition is critical as submarines are frequently exposed to danger under this condition. In this article, the procedures of an integrated simulation to estimate the flow-induced noise considering the submarine operating condition are described. These procedures evaluate both the bubble noise from breaking waves occurring at the free surface and turbulent flow noise from the underwater flow field. To simulate the flow field around a submarine, a two-phase hydrodynamic analysis based on the modified volume-of-fluid model, including air entrainment, was performed. The results of the free-surface shape and activated regions of air entrainment were compared with the experimental observations and showed very good agreement. The hydrodynamic results, including the rate of air entrainment and flow-field data, were applied to the bubble noise model and the permeable forms of the Ffowcs Williams and Hawkings equation to calculate the flow-induced noise of the submarine. Further, the numerical results of the flow-induced noise were validated through a comparison with the experimental result obtained at the large cavitation tunnel in Korea Research Institute of Ships and Ocean Engineering. The result reveals that bubble noise dominated below 500 Hz, whereas turbulent flow noise dominated above 500 Hz. Finally, the estimation of the underwater radiated noise of the flow-induced noise under the far-field condition was performed. The developed procedures can be effectively used to analyze the flow-induced noise from a submarine under snorkel condition and indicate its usability through the quantitative assessment tool in the design stage or risk management of a submarine.