Mass-spring system modelling for biplane membrane flapping wings

This paper presents a novel modelling method to study the thrust generation mechanism of biplane flapping wings made of thin and highly deformable membrane. Based on the principle of strain energy equivalence, the membrane structures were modelled by mass-spring systems. The aerodynamic loads were calculated by a simplified quasi-steady aerodynamic model with consideration of the clap-and-fling mechanism. The impact force was introduced into the system when two wing surfaces were in contact. For wing-dynamics simulation problems, convergence analyses were conducted to obtain suitable mesh resolution. To validate the present modelling method, the predicted thrust and required power of a biplane flapping-wing air vehicle were compared with the experimental data. The effect of the forward speed was also analyzed in this paper. It was shown that as the forward speed increases the thrust production efficiency becomes lower together with smaller wing deformation.