Optimization of kinematic parameters of dragonfly wing section in forward flapping flight

A numerical investigation is conducted on the two-dimensional corrugated wing section of the dragonfly Aeshna cyanea in forward flapping flight mode. The analysis aimed to determine the impact of various kinematic parameters on the aerodynamic performance and to identify the optimal kinematic conditions for achieving maximum mean lift ( C <overline> L m a x ) and minimum mean drag coefficient ( C <overline> D m i n ). In forward flapping flight mode, the insect moves forward by flapping its wings, and the forward velocity is not zero. The study used the QUICK (Quadratic Upstream Interpolation for Convective Kinetics) scheme for spatial discretization of convective terms and first-order accurate implicit for temporal discretization. The dynamic mesh method following the Arbitrary Lagrangian Eulerian (ALE) formulation is used to track the moving interface of rigid wing section in the fluid domain. It has been observed that the maximum of lift and drag occur during the downstroke of flight. The vortical structures are larger in size at the leading and trailing edges when the peak of lift occurs. The larger leading-edge vortex on the lower surface of the airfoil creates a low-pressure region, thus increasing the peak drag. The kinematic parameters of best performance varied depending on the performance parameter being considered. The Pareto optimal front (POF) is obtained using multi-objective optimization method using surrogate models, which is a set of various design points obtained considering the maximum mean lift and lowest mean drag as objectives. From the POF, one can obtain the corresponding drag and optimum kinematic parameters for a particular lift, and vice versa, for an optimum design.