The Effect of Wing Spacing on Tandem Wing Aerodynamics

Abstract

This paper investigated the effect of wing spacing between fore and hind wings on a tandem wing configuration. The aerodynamics of flapping wings in tandem configuration was investigated numerically at Reynolds number of 5000. The flow field simulation was obtained by solving the incompressible Navier-Stokes equations on overlapping grids. Both convection and diffusion terms were discretized with second-order accurate central difference schemes. The tandem wing motion was handled with an overlapping moving grid. The tandem configuration was tested with four different wing gap spacings: 1.0, 0.5, 0.25 and 0.1 of the chord length. Aerodynamic force and power results as well as flow visualizations were shown. Adjusting the wing spacing had a noticeable effect on the resulting flow field and aerodynamic forces. As the wing spacing was decreased, vortex structures around the hind wing became elongated and spread out due to interactions with the fore wing. Total lift by tandem wings was maximized at a wing spacing of 1.0 while thrust was maximized at a spacing of 0.5. Power consumption was minimized at the closest wing spacing, 0.1. Surprisingly, the resultant force and propulsive efficiency of the tandem wings remained nearly constant across all wing spacings.