Aerodynamic effects of wing-wake resulting from phase lag in four-winged flapping flight

A series of wind-tunnel experiments were conducted on a flapping-wing model with two tandem wing pairs, similar to the fore-wings and hind-wings of a dragonfly. This paper investigates the feasibility of using the phase relation between the fore- and hind-wings as a means of flight control by measuring the time-resolved lift and thrust generated by each wing pair for phase relations of 0-360 degrees. It was shown that the forces generated by the hind-wings varied significantly as the phase relation was modulated. Other parameters, including flapping frequency, wing spacing and freestream velocity were also varied to investigate the parameter spaces where phase control was most effective.