Direct numerical simulations of Dragonfly-inspired Tandem Wing Configuration at Low Reynolds Number

Dragonflies are naturally optimized fliers operating at low Reynolds number (Re) of O(10^2-4) and are comparable in size, making them a potent candidate for the design of micro air vehicles. We conducted the direct numerical simulations (DNS) of the tandem corrugated wing adapted from the dragonfly wing at chord Re of 10⁴ and up to 5^◦ angle of attack (AOA). The 6th-order compact finite difference code is used for computations. Initially, Reynolds-averaged Navier Stokes simulations are performed to obtain near-boundary conditions for DNS. This methodology allows the reduction of the computational domain for DNS without compromising the output. Different tandem configurations with an offset gap of up to 0.2 chord length demonstrate that reducing the horizontal gap and positioning the hindwing below the forewing enhances the aerodynamic performance. Generally, the forewing lift increases and its drag decreases relative to its single isolated wing, while it is reversed for the hindwing. However, in a scenario with zero vertical offset and a horizontal gap of 0.1 chord at 3^◦ AOA, the drag reduction is noted in each of the wings. Thus, the tandem configuration is able to reduce drag during the gliding mode of flight, in addition to excellent maneuverability known from the literature.