Effect of viscoelastics layer cover type on characteristics of sound radiation from double cylindrical shell

The finite stiffened double cylindrical shell coated with viscoelastics layers on the inner and outer shell is systematically studied. The shell motion is obtained using the classical Flugge operator. The annular fluid field between the inner shell and outer shell is solved by applying Helmholtz equation and the continuity conditions of the displacement on the surface of fluid-structure, then the expression of sound pressure is obtained by Fourier transform. The layer motion is described by three-dimensional Navier equations. Displacement solutions of Navier's equations are expressed by using Taylor expansion along the layer thickness. The vibration equations of no layer and three cover types of layers are constituted using the different continuity conditions of displacement and stress. The effects of no layer and three cover types of layers on characteristics of sound radiation from three connection types of double cylindrical shells are discussed in numerical calculation. The results show that the layer can reduce the level of sound radiation greatly, and the effect of the double shell coated with viscoelastics layers on the inner shell is better than that of the double shell coated with viscoelastics layers on the outer shell, and the effect of the double shell coated with viscoelastics layers on the inner and outer shell on vibration decrease and noise reduction is the best.