Mechanical and Flow Excited Vibrations of Elastic Plates and Cylindrical Shells in Dense Fluids.
Mechanical and flow excited vibrations of elastic plates and cylindrical shells in dense fluids are presented. The perturbation method is used to connect the basic equations in fluid mechanics and acoustics. A computer model based on a boundary-fitted coordinate transformation is used to solve the two-dimensional incompressible viscous time dependent fluid flow problem. Numerical results for flow over vibrating plates and flow across vibrating cylindrical shells are presented. Several fluid-acoustic-solid interaction problems are addressed in the thesis using a generic block diagram model. These problems include both viscous and inviscid flows over elastic plates and shells. The emphasis in the study has been to determine the near field surface pressure distribution on the elastic vibrators. The surface pressure for the forced vibration of elastic plates in contact with inviscid fluid flow is predicted using time and wavenumber domain approaches. A Mach number dependent modal impulse response representation is also developed. Numerical evaluation shows significant changes in the surface pressure as a function of the Mach number, vibration frequency and mode shapes. The surface pressure on an elastic plate for the coupled fluid-plate problem has been addressed through analytical and numerical approaches. As a result of fluid loading, a set of coupled convolution integral equations is developed by using a modal expansion technique. These equations are solved by the marching forward in time technique. Numerical results for flow over a vibrating plate are also presented. The surface pressure on a cylindrical shell with a specified radial excitation without flow is addressed by a modal expansion technique. A time domain approach to determine the transient displacement and pressure fields of fluid loaded infinitely long cylindrical shell, which are excited by broadband excitations is presented. Numerical results are also presented to illustrate typical characteristics of the displacement field for specified excitations. Finally a coupled hydrodynamic and cylindrical shell numerical model is utilized to evaluate the surface pressure response of a cylindrical shell in contact with a viscous flow across the cylinder. Numerical results are presented to illustrate the nature of the characteristics of the flow field and the shell displacements.
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- Physics: Acoustics; Engineering: Marine and Ocean