Aerodynamic effect of stroke amplitude on hovering performance of three-dimensional tandem flapping wing

Abstract In the present numerical investigation, we studied the effect of forewing and hindwing stroke amplitude (ϕ_o) on the aerodynamic performance of dragonfly (or damselfly) hovering flight. Three-dimensional numerical simulation has been performed for two wings with tandem arrangement flapping along an inclined stroke plane. Simulations were conducted for identical as well as non-identical stroke amplitude of both wings, oscillating with three phase differences: ψ= 0^o,90^o and 180^o. For identical stroke amplitude, the higher stroke amplitude reduces the vertical force coefficients of both wings. During ψ= 0^o, forewing lift enhances significantly for higher stroke amplitude due to LEV interaction. During ψ= 90^o and 180^o, the wing-wing interaction is found to be detrimental to the vertical force coefficient of both wings. The presence of forewing reduces hindwing lift during all ψ, with maximum lift reduction observed for ψ= 180^o. The maximum hovering efficiency for identical stroke amplitude is obtained for ϕ_o= 50^o during ψ= 0^o. For non-identical stroke amplitude, the hindwing lift reduces with an increase in forewing stroke amplitude for all ψ. Also, the forewing lift increases with hindwing stroke amplitude during ψ= 0^o. However, for ψ= 90^o and 180^o, the forewing lift is reduced for higher hindwing stroke amplitude. It was found that non-identical stroke amplitude is detrimental to hovering efficiency of dragonfly flight. The present study will help us to optimize the wing kinematics during the development of dragonfly-inspired MAVs.