2. Introduction

In order to study the behavior of structures filled with fluid, it may be necessary to take into account the phenomena of sloshing, that is to say to add to the fluid-structure coupled system, the effect of gravity at the level of the free surface of the liquid. The structures concerned are, for example, the tanks of fast-moving nuclear power plants, fuel storage pools [bib4].

The developments already carried out in fluid-structure coupling [bib3] have therefore been completed by the introduction of new surface elements which take into account, in their formulation, the effect of gravity.