ASSESSMENT OF CLASSICAL NUMERICAL MODELS FOR THE SEPARATE FLUID-STRUCTURE MODAL ANALYSIS

In the numerical analysis of the eigen behavior of huge liquid-storage tanks, treatment of large-scale matrices becomes a burden owing to the hydrodynamic interaction between two different media, structure and liquid. In order to overcome such a problem, it is classical to split the dynamic system into two separate problem regions, the structure and the liquid, by utilizing the mass-adding technique. In general, the eigenbehavior of interior liquid is characterized by the sloshing mode while that of the structure by the bulging mode, and furthermore the two modes exhibit a weak coupling. Based upon this weak coupling, the structure deformation to the sloshing mode and the liquid free-surface fluctuation to the bulging mode have been neglected in the classical added-mass computation. This paper is concerned with the refinement and the assessment of classical interaction modelling by including both neglected effects. In order to estimate the accurate mass added to the structure, we refine the classical procedure by reflecting the liquid free-surface fluctuation. On the other hand, we qualitatively and quantitatively analyze the additional effect by the structure deformation onto the classical rigid-tank sloshing model. Through the numerical experiments carried out with a representative cylindrical liquid-storage tank, we illustrate our theoretical results.