Rayleigh-Ritz method and substructuring in the study of the free vibrations of fluid-structure interacting systems

摘要

This papers deals with the free vibrations of structures coupled with inviscid fluid when there is no cavitation at the interface. An analytical-numerical technique to study fluid-structure systems is the Rayleigh-Ritz method. In particular, it gives a linear eigenvalue problem for an incompressible liquid when the free surface waves are neglected; when free surface waves and compressible fluids are considered, a nonlinear eigenvalue problem is obtained. When the solid coupled with the fluid is a structure obtained connecting simple components (substructures) together, it is useful to use a method to synthesise substructures. An approach particularly suitable for this purpose is the use of artificial springs, simulating the junctions between the substructures, in the application of the Rayleigh-Ritz method for coupled fluid-structure systems. In this paper we propose this method to study fluid-loaded structures. All the substructures in contact with the same fluid volume are not only coupled by joints but also by the fluid itself. The method is applied to a storage tank partially-filled with water.