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. (C) 2001 Academic Press.