Fig 1 - available via license: CC BY
Content may be subject to copyright.
Source publication
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...
Citations
... In the anechoic chamber wind tunnel, Li et al. [16] verified that the frequencies of the different scale cylinders satisfy the similarity of the Strouhal number, and they studied the similarity in different media based on the FW-H numerical method. There were abundant numerical calculations to discuss the submarine performance under small-scale models, including resistance characterization [17], flow characterization [18], radiated noise [19], and self-noise [20]. As for the full-scale model, Sezen et al. [21] analyzed the scale effect of the submarine's hydrodynamic performance based on the Reynolds-averaged Navier-Stokes (RANS) method. ...
As one of the three major noise sources of submarines, flow-induced noise plays a key role for the stealth capability of submarines. Several research studies based on experiment or simulation have evaluated the sound radiation from the scale model; however, it is still a great challenge to efficiently evaluate the flow-induced noise of a large-scale prototype. In order to solve this problem, the flow-induced noise of different scale submarines is analyzed, and both the similarity law and the scale effect are discussed in the dimensionless frequency St = 10–1089. The fully appended DARPA SUBOFF, a famous benchmark submarine model, is used in our research. The relationship between the sound power, scale variables, and the speed and scale variables is obtained using the Buckingham Pi theorem. Then, the sound pressure level and the sound power level of the SUBOFF, with the scale ratio of 1:24 and 1:48 and the speed of 2, 4, and 8 m/s, are calculated based on the large-eddy simulation (LES)/Lighthill hybrid method. Finally, the scale effect between a hypothetical prototype (actually, a benchmark SUBOFF model with a scale ratio of 1:8) and its scale models are discussed at the same speed. The numerical results show that the submarine’s sound power level conforms to the similarity relationship of dipole source within the cut-off frequency St = 100. The error of the sound power level is about 20 lg ( φ ) caused by scale effect when the dimensionless frequency is greater than the cut-off frequency, where φ is the scale ratio from the hypothetical prototype to the model. The scale error of the sound pressure level at different position and different frequency exist differently when extrapolating from model results to prototype according to the similarity law based on dipole source.
Application of the reciprocity principle to evaluate the acoustic radiation from arbitrary multilayered fluid and solid materials is described. To include the effect of shear motion in surrounding media, including viscosity in a fluid, equations for the acoustic radiation from such materials under point force excitation are developed in terms of reflection and transmission coefficients for longitudinal and shear waves. Calculations for forcing on either side of the layered material and in arbitrary directions, and for any asymmetric layer arrangements, are conducted. The frequency range of the calculations is not restricted by thin-plate or thick-plate theory. The test case for the radiation from plates embedded in a viscous and attenuating fluid has been investigated in detail. The effect of viscosity and attenuation has been quantified and shown to be significant at high frequencies. Application to the problem of flow noise is also briefly discussed.
