Verification of underwater radation efficiency using FE/BE coupled model and measurements

The underwater radiation efficiency is an important measure to understand the noise radiation characteristics of underwater structures. In this paper, we investigate the characteristics of the measurement methods of the underwater radiation efficiency using the simulations by validated FE/BE coupled computer model, and compare the radiation efficiencies for a real underwater structure. Numerical simulations of the underwater radiation efficiency for the spherical shell which was validated with analytic solutions showed that the near-field and the far-field measurements in the low frequency band can overestimate the radiation efficiency and the error in the near field method can reach 10 dB. Next, the underwater real structure was modeled using the FE/BE coupled approach. The calculated radiation efficiency and the simulated ones for the two experimental set-ups using the FE/BE coupled model were compared with those of the measured ones. The comparison showed not only that the FE/BE coupled model can accurately simulate the characteristics of the underwater radiation efficiency considering the experimental set-ups, but also the radiation efficiency might have been underestimated due to the approximations introduced in the experimental measurements.