Research on Hydrodynamic Characteristics and Spatial Evolution of Flow Noise of High-speed Submarine
Submarines are significant naval combat weapons in contemporary times.The hydrodynamic and noise characteristics are important reference criteria for the performance of submarines.At the same time,submarines are constantly developing towards higher speeds.Therefore,the SUBOFF fully attached submarine model is take as the research object in this paper,and RNG k-εturbulence model and FW-H acoustic model in FLUENT are used to study the hydrodynamic characteristics and the spatial evolution law of flow noise of submarine under high-speed conditions(20.00 kn,30.00 kn and 40.00 kn).The resistance on the surface of the submarine,as well as the distribution characteristics of pressure,velocity and vortices on the surrounding flow field of the submarine are specifically studied.The influence of speed changes on the hydrodynamic characteristics is also analyzed.It is found that when the submarine moves underwater,the pressure on its wall is proportional to the square of the speed.The peak velocity of the submarine's surrounding flow field is about 1.36 times the speed of the submarine.And as the speed increases,the horseshoe vortex gradually moves away from the fairwater and stern appendages,the tail vortex becomes thicker and longer,and the vortex motion increases.In addition,the total sound pressure level,sound pressure frequency curve and sound power density curve of flow noise at characteristic points under different speeds are analyzed.It is found that when the speed is doubled,the flow noise at characteristic points increases by about 6 dB,and the sound power is mainly concentrated at 0～3 500 Hz.The effects of speed and radiation radius on the directionality of flow noise in the longitudinal and transverse planes of submarine are explored,the attenuation laws of flow noise in the head-tail direction of submarine at different speeds are compared.It is found that the radial directionality is stronger than that in the head-tail direction of submarine.As the radiation radius increases,the radial directionality becomes more significant,and the aspect ratio k of the total sound pressure level in the radial and head to tail directions shows a logarithmic increasing trend with the expansion of the radiation radius.The noise attenuation in the upstream flow of the submarine is faster than that in the downstream,and gradually tends to be consistent with the increase in distance.The speed of a submarine has a minor impact on the directionality of sound,but has no significant impact on the attenuation law of far-field flow noise.Finally,an expression is fitted for the attenuation law of flow noise with changes in radiation radius and speed,with a correlation of over 0.99.This paper is of great significance for further optimizing the submarine profile to improve its flow and noise performance,and enhance its comprehensive combat capability.
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