An Experimental Investigation on the Wake Flow Characteristics of Tandem Flapping Wings

The use of tandem wings in flapping flight is considered a unique and interesting concept in the area of applied aerodynamics. Dragonflies using the tandem wing configuration have been observed to be some of the most agile and maneuverable predators in the animal kingdom. This leads us to further investigate the advantages of tandem wings and how their application in bio-mimetics can aid in the development of future nano air vehicles (NAVs). Using bio-inspired propulsion methods such as flapping wings, these micro-scaled unmanned aerial vehicles (UAVs) would be operating within the Reynolds number range of insects. For the current experimental study the wing spacing between tandem piezoelectric wings are varied to different values with respect to the chord length of the wings. A high-resolution Particle Image Velocimetry (PIV) system was used to quantify the time evolution of the unsteady wake vortex structures. The measurements were performed at wing spacing values of 0.15C, 0.5C, 1C, 1.5C and 2C between the fore-wing and the hind-wing for a chord Reynolds number of 1,000and a Strouhal Number (St) of 0.3.