Numerical investigation of the aerodynamic benefits of wing-wing interactions in a dragonfly-like flapping wing

摘要

Numerical simulations are performed to investigate the aerodynamic benefits of wing-wing interactions on a dragonfly-like flapping wing while hovering, at a value of Reynolds number Re set to 630. The local phase shift psi and wing spacing L* (L/c) are varied to observe their influence on aerodynamic performance. The results show that the aerodynamic benefits due to interactions are strongly dependent on both psi and L*. The wing-wing interactions are beneficial for the in-phase stroking pattern at psi = 0 degrees when 1.2 <= L* <= 2.3, while it is extremely detrimental for the counter stroking pattern at psi = 180 degrees when 1.2 <= L* <= 2.3; these benefits and drawbacks are dependent on the timing of the interactions. The best case, when psi = 0 degrees and L* = 2.1, can increase the time-averaged vertical force coefficient (C) over bar (v) up to similar to 10 % in comparison to the without-interaction case. Two unsteady flow features namely the enhanced dipole structure and the in-sync of wake capture and wing-wing interactions are observed that increase the vertical force generation in hovering dragonflies. The overall downward momentum imparted by the wing is larger for psi = 0 degrees in comparison to psi = 180 degrees as the wake has high vertical velocities due to the constructive role played by wing-wing interactions.