Analysis of natural frequency of free damping composite cylindrical shell submerged in viscous fluids

The effect of fluid viscosity and material parameters of the damping layer on the natural frequency characteristics of a circular cylindrical shell covered with free damping layer immersed in a viscous acoustic medium is studied in the present paper. An equivalent method is applied to the damping layer coated on the surface of the cylindrical shell. Then, the wave equation for viscous flow field derived from the linear equations of continuity, Navier-Stokes and state, the Flugge's thin shell theory for the isotropic, elastic, thin cylindrical shell and the appropriate wave harmonic field expansions in association with the pertinent boundary conditions are employed to get the equations of motion and the characteristic equation in the coupled system. Subsequently, numerical analysis is applied to solve the characteristic equation for the coupled system at various material parameters and viscosity coefficients, the influence of which can be illustrated by the calculation results.