Investigation of the oblique-flow-induced flow mechanism and acoustic characteristics of the submarine

Abstract

To study oblique-flow-induced hydrodynamic mechanisms and acoustic characteristics, this study employs a combination of Large Eddy Simulation and the Ffowcs Williams–Hawkings equation to analyze the flow field and flow noise of an underwater vehicle at a sailing velocity of 6 kn, under oblique flow angles of 0°, 2°, 4°, 6°, 8°, and 10°. The pulsating pressure on the sail surface was measured in the towing tank at Northwestern Polytechnical University to validate the numerical method, and the method performed favorably. The results reveal that the hull lateral force is the most sensitive to the orientation of the oblique flow. Even a minor oblique flow angle of only 2° generates a lateral force reaching 76.12 N. As the oblique flow angle increases from 0° to 10°, the overall resultant force rises by 460.85%, accompanied by lateral migration of the stagnation point along the sail leading edge. Such flow field evolution primarily modulates the amplitude of surface pressure fluctuations while exerting a marginal influence on flow-governed natural frequencies. Meanwhile, oblique flow reshapes the directional features of submarine flow noise. In the horizontal plane, the acoustic radiation footprint on the leeward side expands with increasing noise levels, whereas the windward radiation region contracts, driving the flow noise directivity to transition from symmetric to asymmetric.