The investigation on calculating and measuring fluid noise from underwater viscous elastic materials

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 model of sail hull in the software, ANSYS, is built up. Then, fluid field is calculated by the software, Fluent. After the data is dealt with by fast fourier transform, namely, FFT, sound radiation power of the model can be calculated by the software, ACTRAN. Then, viscous elastic materials have been put on the surface of the model. Sound radiation power of the model with viscous elastic materials can be calculated by the listed process. The results indicate that total level of sound radiation power from viscous elastic materials is proportional to 3-6 times of fluid velocity. After that, the model of sail hull has been designed, of which the length and height are 0.4m, 0.17m, respectively. The thickness of the model and viscous elastic materials is 0.002m, 0.005m, respectively. The experiment has been done in a water tunnel, which is induced by the gravity of water, so that the level of background noise is especially low. The velocities of fluid are 2.98m/s, 6.34m/s, 8.68m/s. Sound radiation power of the model and that with viscous elastic materials has been measured by reverberation method. The total level of sound radiation power decreased by viscous elastic materials is 5 dB. The results are coincided well with that calculated by the software. The results indicate that the method of calculating and measuring sound radiation power of viscous elastic materials is perfect.