Study on hydrodynamic noise characteristics of stiffened cylindrical shell with multilayer gradient acoustic coating

In this paper, the hydrodynamic noise characteristics of a finite stiffened cylindrical shell submerged in water are studied. The shell is covered with a multilayer gradient acoustic coating, and its outer surface is subjected to excitation of turbulent boundary layer (TBL) pressure fluctuations. The power spectral density (PSD) function of the modal pressure induced by TBL pressure fluctuations is computed using two analytical methods: the direct extension method and the comb function method. These methods extend the TBL wavenumber-frequency spectrum from planar to cylindrical surfaces through different approaches. Furthermore, the hydrodynamic noise predicted by these analytical methods is compared with results obtained via the finite element method and the statistical energy analysis (SEA) method. The comb function method is demonstrated to be more effective in accurately predicting the hydrodynamic noise of finite cylindrical shells. Additionally, variations in the acoustic impedance, density and sound velocity of the coating in the radial direction are explored to determine their impact on hydrodynamic noise control. The results show that, compared to an uncoated shell, a multilayer gradient acoustic coating with optimized parameters can significantly attenuate the hydrodynamic noise of a finite stiffened cylindrical shell.