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The sloshing effects of an internal fluid on the flutter envelope of an aeroelastic system have received little attention in the open literature. This issue is nevertheless relevant for many aircraft, especially high-performance fighter jets carrying stores. This paper addresses some aspects of this problem as well as related modeling and analysis issues. These include the importance or insignificance of accounting for the hydroelastic effect when modeling an internal fluid and its container as well as accounting for that container when modeling the aerodynamics of the overall aeroelastic system. The paper also reports on the findings of four independent sets of flutter analyses performed for a wing-store test configuration and various fuel fill levels in the subsonic, transonic, and early supersonic regimes. Two of these sets of numerica l experiments relied on a computational-fluid-dynamics-based computational technology, and two of them on the doublet-lattice method or a supersonic lifting-surface theory, where applicable. The geometry of the chosen test configuration is that of the AGARD Wing 445.6 with a blunt-nosed store. The obtained computational results show that, at least for the considered wing-store configuration, ignoring the aforementioned hydroelastic effect tends to overestimate the added-mass effect and underestimate the critical pressure and flutter speed. They also reveal that, whereas the aerodynamics of the store may be neglected in the subsonic regime, they cannot be ignored in supersonic air streams. Finally, the performed computational study suggests that, in general, the critical pressure and flutter speed decrease with an increasing fuel fill level.

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