Numerical Analysis On Flapping Foils Based On CFD

Underwater vehicle has brought great benefits to mankind and gets the attention of the countries when ocean development becomes increasingly important. It can collect the hydrological information, be used in anti-submarine warfare, and play an extremely important role in the future of ocean. With the improvement of civil and military requirements, however, the existing vehicle gradually can't satisfy people's needs.The optimal propulsion performance of fish has gasped people' attention for a long time.In this paper, the hydrodynamic performance of a 2D rigid oscillating hydrofoil NACA0012 is analyzed using the commercial software FLUENT, mean thrust flapping foils produces match well with theoretical estimated value by B.Ahlborn. In order to clarify the effect of WIG(Wing-in-ground) and chordwise flexibility on flapping foils' propulsion performance,thrust force and wake pattern of four oscillating models, including single-rigid ?single-flexible?dual-rigid and dual-flexible foils were calculated. Simulation results show that the deflection of reverse von Karman wake depands on the vortex diplore structure close to foils;In our study,when0? exceed 25,the wake is likely to deflect;The wake bifurcating has something to do with the vortex separation and combination;The flexibility of flapping foil has two antithetic effect on its wake structure: increasing the0? which stimulates deflection and deceasing the gap between two vortex in a diplore which constrians deflection.