Frictionless liquid sloshing in circular cylindrical container configurations

If the free liquid surface in a circular cylindrical container is covered with solid structural parts, the natural frequencies and the response of the liquid in the container is drastically changed. This is also expressed by a much lower flow behavior inside the container. The benefit of a partly covered free surface plane lies in the shifting of the natural propellant frequencies above and away from the control frequency of a space vehicle, and in the decrease of the sloshing masses participating in the dynamic motion of the system. The fundamental natural frequency of a non-viscous and incompressible liquid has been determined for increasing width of an annular ring baffle attached to the tank wall. With increasing structural coverage of the free surface the natural frequencies increase considerably. The response to translational excitation has also been numerically evaluated and shows the shifting of the resonances to higher values. The procedure presented here may without any difficulties also be applied to various arbitrary coverages of the free liquid surface. It may also be used as a test case for purely numerical methods, such as finite element methods and others.