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There usually exist rubber materials in the outside of underwater navigators. In one aspect, sound radiation from these navigators can be reduced by the materials, and it is beneficial to control the pollution of noises in ocean environments. In the other aspect, the resistance induced by the fluid can be decreased, and it is helpful to enhance the speed of these navigators. In the paper, a numerical...
Based on the combination of large eddy simulation theory and Lighthill's acoustic analogy equation, numerical simulation of underwater flow noise is investigated. The calculation model of nozzle and fluid is built up by finite element software, ANSYS. The property of fluid field is calculated by the software, Fluent, which is in the ANSYS. The fluid property changing with time is gotten and dealt...
An underwater open cavity, such as a submarine's open weapons firing tube, is a typical kind of structure that can induce fluid noise. To study the fluid noise generated by the submarine's open tube, greater attention is paid when the cavity's opening is vertical to the flow direction. This paper focuses on flow noise induced by an underwater cavity having openings under small attack angles, and simulations...
For underwater acoustic measurement experiment, if the scale of underwater elastic structure is large, it is difficult to achieve the requirement of the classic far-field testing criterion. This paper has researched the measuring distance criterion for underwater structure radiated noise from the perspective of energy measurement. A concept of measuring distance criteria is derived responding to the...
A prediction method of submerged structure sound radiation is presented, in which the measured structure vibration data is processed to obtain sound radiation by a transfer method. For an underwater vehicle, its own vibration and sound radiation usually needs to be known accurately. Therefore, accurate prediction of sound radiation from submerged structures is of great significance. As we know, the...
The far-field distance of underwater structure sound sources is usually considered, especially in underwater acoustic combat, target detection, vibration reduction and noise control. There exist two formulas for the determination of far-field distance. One is derived from a uniformly vibrating piston in a rigid boundary. The other formula is usually used in finite element software. However, underwater...
In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green’s function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined...
Based on wave superposition method (WSM), radiated noise can be predicted quickly by monitoring the vibration data on machine surface. However, this method may produce great error for complex vibration distribution. The main cause is the improper configuration of equivalent sources. In order to solve this problem, an equivalent source configuration based on the least mean square method (LMS) is put...
A method for calculating the sound radiation of underwater cylindrical shells in low frequency band by using the equivalent beams is investigated in this paper. The vibrations of cylindrical shells with large length-to-radius ratio L/a>10 are similar to those of beams in very low frequency band, in which underwater sound radiation characteristics of cylindrical shells are mainly dominated by beam-type...
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