Resonant Frequencies in a Spherical Elevated Container Partially Filled with Water: FEM and Measurement

Abstract

In this paper, a numerical-experimental study about the dynamic response of coupled fluid-structure systems of spherical elevated tanks is presented. The main objective is to gain insight in the physical response of this particular structural typology that is widely used in the petrochemical industry as LPG containers.
Experimental tests on a model were performed identifying the main fundamentals parameters involved in the physical response and determining the natural frequencies that contribute to the response in the range of 1-5 Hz, for different liquid levels. Next, a numerical model that takes into account the coupling between fluid and structure were developed and validated against the experimental results. A very good agreement was obtained between experimental and numerical results.
The obtained results indicate that the sloshing has a significant effect on the dynamics characteristics of the systems and, in the analyzed case, a two mass model it is insufficient to describe the overall dynamic response. In order to obtain a simple lumped mass model, a minimum of three masses and then three degree of freedom is suggested.