Analytical modeling of sound transmission through FGM sandwich cylindrical shell immersed in convected fluids.

The main objective of this research work is focused on the acoustic response analysis of functionally graded material (FGM) sandwich cylindrical shell structure immersed in convected fluids. In the analysis, two common types of FGM sandwich cylindrical shells are considered, which include one with FGM face shell and homogeneous ceramic or metal core, and the other with FGM core and homogeneous face shell. Given the structure is immersed in a mean flowing fluid of velocity tangential to the acoustically deformed boundary and it is excited by an incidence oblique plane wave. Fluid–structure coupling is considered by imposing velocity continuity condition at fluid–structure interfaces. By comparing the numerical results with the existing solutions in open literature, the validity of the proposed theoretical model is verified. Finally, based on the developed theoretical mode, the influences of the gradient index, sandwich type, external mean flow, and skin-core-skin ratios on the structural sound transmission performance of FGM sandwich cylindrical shell have been investigated, wherein the first resonance dip shift noticeably to high frequency as the Mach number is increased, and case II has the largest amplitude fluctuation and the lowest STL curve magnitudes, in addition, when M 1 = M 2 > 1.2 , two branches, including positive refraction branch and the negative refraction branch, are found in the contour plots under opposite flow direction conditions, and the large skin-core-skin ratio is beneficial to improve the sound insulation characteristics of structures. [ABSTRACT FROM AUTHOR]