Fluid-Structure Interaction (FSI) may contribute significantly to the structural demands on fluid storage structures during the seismic events because of sloshing and impulsive wall pressure. A variety of simplified approaches are used in engineering practice to quantify the FSI effects via either closed-form solutions or the use of discrete analogs to represent the fluid domain. Recent advances in computational technologies have made possible the efficient analysis of real world FSI problems by explicit presentation of the fluid domain in 3D. Different techniques of modeling the fluid domain in LS-DYNA including the Lagrangian and Arbitrary Lagrangian-Eulerian (ALE) methods are discussed in this paper. The utilized technique of coupling of the structure with the fluid is similar to that used for contact simulation. The ALE methods are attractive because the large deformations within the fluid domain can be accommodated without the potential mesh distortion problems faced in the Lagrangian method. Mesh distortion, if it becomes severe, may lead to progressively smaller explicit integration time steps and eventual instability of the solution. On the other hand, the ALE method is relatively expensive as compared to the Lagrangian one due to additional advection, interface reconstruction, and coupling calculations. The analysis results show that although representation of the fluid with Lagrangian finite elements may provide similar wall pressure demands, the wave height estimation may be unconservative compared to the ALE method. It is shown that explicit modeling of the fluid provides realistic presentation of FSI and such analyses can be accommodated within the budget and schedule of the real-world fast-pace civil engineering projects.

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