Analytical Study on Lift Performance of a Bat-Inspired Foldable Flapping Wing: Effect of Wing Arrangement

Abstract

In this work, we use a three-dimensional computational fluid dynamics (CFD) simulation to comprehend how the two wing arrangement variables, i.e., inner/outer wing proportion and mid-stroke dihedral, affect the lift characteristic of a bat-inspired span foldable flapping wing. The employed flapping mechanism is based on previous work. In this study, the structure parameters of the flapping mechanism remain unchanged across all simulations. Based on the CFD results, the tendency and work point regarding maximum lift generation can be found by changing both of the variables. As a result, when modifying the inner/outer wing proportion without changing the total wing shape and area, the maximum time-averaged lift appears in the case of the inner wing occupying half of the semi-span. In addition, when changing the dihedral, the maximum time-averaged lift was obtained when the inner wing dihedral was equal to zero. To discuss the lift variation of the foldable flapping wing, pressure distribution and vorticity of the flow field at certain time points were provided corresponding to the instantaneous lift curves. The conclusions of this research are able to help understand the wing arrangement of birds and bats issued from natural selection, and also support the future design of flapping wing micro-aerial-vehicles.