Abstract
Hydrodynamic noise is one of the three major noise sources of underwater vehicles. The sonar dome is a device placed in front of the ship and the submarine to absorb the flow fluctuation and to reduce the hydrodynamic noise, so that the sonar inside the dome is not affected by the external fluid. However, with the increase of the velocity of ships and submarines, cavitation can usually form in the bulge of the sonar domes, which will bring high level of noise to the sonar. The internal self-noise of the sonar dome mainly comes from two areas: the leading-edge stagnation point and the transition zone of boundary layer. In the paper, we designed the leading-edge serrations and dimples in the leading-edge and transition areas of the sonar dome respectively to reduce the movement resistance and prevent the separation of the boundary layer. The research on leading-edge serrations and dimple technology is carried out by using theoretical analysis, numerical calculations. The results show that the leading-edge serrations and dimples can add energy from the outer flow into the boundary layer; the cavitation phenomenon can be delayed. The hydrodynamic noise has been suppressed by about 20dB.
Highlights
1.1 The function of sonar domes The sonar is a device, which detects the direction, location, and characteristics of the objects in the ocean by the propagation of sound waves in the water
Dyer[1] established the model of the sonar dome, which is an elastic plate covering on the rectangular cavity, and calculated the noise in the rectangular cavity, which is excited by the turbulent fluctuation pressure of the elastic plate
The inside self-noise of the sonar dome mainly comes from two areas: the leading-edge stagnation point and the transition area of the boundary layer
Summary
1.1 The function of sonar domes The sonar is a device, which detects the direction, location, and characteristics of the objects in the ocean by the propagation of sound waves in the water. A dome with good hydrodynamic performance needs to be placed outside the sonar array, to avoid the impact of water flow, reduce the turbulence and suppress the cavitation, and even refrain the direct interference of the arrays by the ‘pseudo-sound’. The pressure and the velocity of the particle in the turbulent boundary layer formed near the sonar dome have intense fluctuations, which radiates the noise directly. It requires the performance of low noise and high mechanical intensity, even good level of sound transmission and minimum acoustic beam distortion. The research on the sonar dome is mainly focused on the optimization of the line, structure and material to reduce the drag and hydrodynamic noise
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