A unified calculation method for acoustic radiation characteristics of variable stiffness cylindrical shells

A unified method for predicting acoustic radiation from variable stiffness cylindrical shells is presented, integrating the Ritz method and the equivalent source method (ESM). Vibration and radiation are treated as a coupled system to eliminate the need for prior surface velocity. Based on first-order shear deformation theory (FSDT), the energy equation is constructed, and boundary conditions are achieved via the penalty method. By incorporating acoustic pressure work, the vibro-acoustic coupling matrix is derived, and the governing equation is combined with the ESM to solve vibration and sound simultaneously. A matrix-scaling factor is introduced to alleviate the ill-conditioning caused by the penalty method. The numerical results demonstrate good convergence and agree well with the simulation results. Comparisons between the results obtained in water and air clearly demonstrate the influence of fluid loading. The vibro-acoustic behavior of laminated, functionally graded, and variable-thickness shells is analyzed, demonstrating the influence of layup angles, gradient parameters, and thickness ratios on natural frequencies and acoustic pressure.