Static aeroelastic analysis of very flexible wings coupled with distributed propellers

Abstract

Distributed propellers are widely used as propulsion for high-aspect-ratio long-endurance UAVs, and their load and slipstream will change the structural and aerodynamic characteristics of the wing, making geometric nonlinear effects more prominent. To address the aeroelastic interference of distributed propellers on the large flexible wing, firstly, on the basis of the vortex theory, a slipstream tube model is used to rapidly calculate the induced velocity of the slipstream, realizing the coupled aerodynamic modeling of the propeller and wing. Secondly, the coupled modelling of propellers and the nonlinear structure is achieved through the derivation and transformation of the coordinate system in the co-rotation method. Finally, combined with the space beam spline, a nonlinear static aeroelastic analysis framework for the large flexible wing considering the effects of distributed propellers is established. The simulation example of flexible wing with distributed propellers shows that the propeller pull will cause negative twisting of the wing due to large deformations, resulting in approximately 10% loss of lift and 20%-40% decrease in static stability margin; the propeller slipstream will change the local flow velocity and the angle of attack, bringing about 2.5% lift gain and 2%-8% increase in static stability margin; propellers increase lift when it is close to the wing root, but decrease when close to the wing tip, and the closer to the wing tip, the more significant the effect is. The analysis method established in this paper can provide guidance for the coupling design of distributed propellers and large flexible wings.

Keywords

• distributed propellers
• slipstream
• flexible wing
• geometric nonlinearity
• static aeroelasticity