Abstract: A platform-sling model is established to study the dynamic response of airdrop platform. An uniform equivalent point Newton-Rapshon iteration method is presented. In order to study the unsteady fluid behavior, the time domain is discretized, and an ALE base finite volume method is used to solve the NS equations. The aero-force is obtained and imposed on the platform. The equivalent point method is validated through commercial software RECURDYN. The results show that the equivalent point method can well represent the slack-taut cases of the sling system. It can also be found that the laminar flow model is used to describe the acting force of fluid on plate well at low Reynolds number. Finally, the comparisons are made between the steady and unsteady FSI models. The time history of unsteady fluid force displays severe oscillation while the steady fluid force varies evenly.

Key words: fluid mechanics, unsteady flow, equivalent point, airdrop cargo platform, fluid-structure interaction