Unsteady aerodynamic characteristics of a seagull wing in level flight are investigated using a boundary element method.Anew no-penetration boundary condition is imposed on the surface of the wing by considering its deformation.The geometry andkinematics of the seagull wing are reproduced using the functions and data in the previously published literature.The proposedmethod is validated by comparing the computed results with the published data in the literature.The unsteady aerodynamicscharacteristics of the seagull wing are investigated by changing flapping frequency and advance ratio.It is found that the peakvalues of aerodynamic coefficients increase with the flapping frequency.The thrust and drag generations are complicatedfunctions of frequency and wing stroke motions.The lift is inversely proportional to the advance ratio.The effects of severalflapping modes on the lift and induced drag(or thrust)generation are also investigated.Among three single modes(flapping,folding and lead & lag),flapping generates the largest lift and can produce thrust alone.For three combined modes,both flapping/foldingand flapping/lead & lag can produce lift and thrust larger than the flapping-alone mode can.Folding is shown toincrease thrust when combined with flapping,whereas lead & lag has an effect of increasing the lift when also combined withflapping.When three modes are combined together,the bird can obtain the largest lift among the investigated modes.Eventhough the proposed method is limited to the inviscid flow assumption,it is believed that this method can be used to the designof flapping micro aerial vehicle.
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