Load analysis method of very flexible wing/propeller system

Light structure weight and large elastic deformation make the geometric nonlinearity of the large aspect ratio airplane that uses propeller as propulsion very remarkable. In one aspect, the load and slipstream of the propeller will cause strong interference on the flow field of the wing. In the other aspect, when the wing is bearing aerodynamic force, it makes large deformation. Thus, the traditional linear analysis based on the small deformation hypothesis is no longer suitable. In this paper, a new method for static aeroelastic analysis and aerodynamic loads computation of the flexible wing with propeller system is presented. The Blade Element-Momentum theory is applied to calculate the load and aerodynamic parameters of the propeller system. Then a Rankine vortex core is placed on the propeller's installation shaft to simulate the propeller effect that makes the wing's flow field in the propeller influence area has an axial velocity increment as well as a rotation speed on the flexible wing. Further, the 3-D lifting-line method is utilized to calculate the steady aerodynamic loads of the curved bending wing who has downwash from the propeller slipstream as well as the horseshoe vortices. Then the generalized surface splines and large deflection interpolation is adopted to solve the geometrical characters of structure/aerodynamic coupling problem and get the information that the aerodynamic computation needs. Finally for a very flexible rectangular wing model with propeller system, the geometric static aeroelastic analysis is carried out. Its application in preliminary design and quick analysis is promising.