Cylindrical shell submerged in bounded acoustic media: A modal approach

The dynamics of a simply supported cylindrical shell submerged in liquid hydrogen and liquid oxygen are considered. The shell itself is bounded by a rigid outer cylinder with closed rigid ends. This configuration gives rise to two fluid-filled cavities - an inner cylindrical cavity and an outer annular cavity. Such geometries are common in rocket engine design. The natural frequencies and modes of the fluid-structure system are computed by combining the rigid wall acoustic cavity modes and the in vacuo structural modes into a system of coupled ordinary differential equations. Eigenvalue veering is observed near the intersections of the curves representing natural frequencies of the rigid wall acoustic and the in vacuo structural modes. In the case of a shell submerged in liquid hydrogen, system frequencies near these intersections are as much as 30% lower than the corresponding in vacuo structural frequencies. Because of its high density, the frequency reductions in the presence of liquid oxygen are even more dramatic. The forced responses of a shell submerged in liquid hydrogen and liquid oxygen, while subject to a harmonic point excitation, are also presented. The responses in the presence of fluid are found to be quite distinct from those of the structure in vacuo.

Duke Scholars

Author Lawrence N. Virgin Thomas Lord Department of Mechanical Engineering and Materia ...