Coupled BEM and FEM Analysis of Fluid-Structure Interaction in Dual Compartment Tanks

The paper presents a fluid-structure interaction analysis of fuel tanks with cylindrical and spherical compartments partially filled with a liquid. The compound shell of revolution is considered as a con- tainer model. The shell is supposed to be thin, so the Kirchhoff–Love linear theory hypotheses are applied. The liquid is an ideal and incompressible one. Its properties and filling levels may be different within each compartment. The shell vibrations coupled with liquid sloshing under the force of gravity have been considered. The tank structure is modelled by a finite element method, whereas liquid sloshing in the compartments is described by a boundary element method. A system of singular integral equations is obtained for evaluating the fluid pressure. At the first stage, both spherical and cylindrical fluid-filled unconnected rigid shells are considered. Different filling levels as well as small radii of free surfaces are taken into account in problems of liquid sloshing in spherical shells. The sloshing frequencies in the presence of complete or partially covered free surfaces are determined for cylindrical shells. The boundary element method has proven to be effective and accurate in all the problems considered. At the second stage, the natural frequencies and modes of the dual compartment tank are obtained including sloshing, elasticity, and gravity effects.