Theoretical Research On The Interaction Of The Flow Past Multi-wing In Two-dimension And Design Method Of Multi-wing

There were many multi-wing structures or multi-wing issues in engineering application,including grid fins and WIG.Based on potential theory and linear thin wing theory,a theoretical research on the flow past multi-wing in two-dimension was addressed,and the interaction of the flow past multi-wing in liquid,gas and cavity was the key point.The total aerodynamics or hydrodynamics of the multi-wing was intensely affected by the interaction of multi-wing,meanwhile,the interaction phenomenal might be taken considered into the designation of multiwing.In the case of the interaction of multi-wing,in common flow,theoretical method and numerical method were adopted,respectively,and a quick estimate method and discrete vortex method were obtained.The result showed that interaction phenomenal existed in the multi-wing,the degree of which was closely related with the pitches of multi-wing.Besides,the effect of interaction was relied on the spatial arrangement of multi-wing.Based on the quick estimate method,the pitches were optimized and the optimal distances of foils to maximize the total lift force were obtained;in cavity flow,the linear cavity theory of single foil was extended to the cavity flow of multi-wing,meanwhile,an iterative method was utilized to compute the length of every foil in the case of a certain cavity number.The result showed that the interaction phenomenon was more intense and complicated than that in common flow.The shape and length of cavities on every foil was different,even foils in symmetrical placement,so was the hydrodynamics of every foil in multi-wing.In the case of designation of multi-wing,refer to the design scheme about NACAa series and for the purpose of homogenizing the load distribution,a design scheme about the mean lines of multi-wing was built in consideration of the interaction of multi-wing.The mean lines of WIG and multi-wing were designed respectively by the design scheme,and the mean lines were obtained at different linear load parameters and relative locations.And the result showed the mean lines of multi-wing were different from single foil.In the designation of WIG,a same lift force could be achieved in a relative small camber.In the designation of grid fins,the cambers of foils were unequal in case of same lifts because of the interaction,which meant the foils need to be designed according to the setting lift force.