Effect of flapping kinematics on the mean lift of an insect-like flapping wing

An experimental investigation of the effects of varying flapping kinematics on the mean lift produced by an insect-like flapping wing in hover is presented. This was performed with application to flapping-wing micro-air vehicles (FMAVs) in mind. Experiments were accomplished with a first-of-its-kind mechanical flapping-wing apparatus capable of reproducing a wide range of insect-like wing motions in air on the FMAV scale (similar to 150 mm wingspan). This apparatus gives an insect-like wing the three controllable degrees of freedom required to produce the three separate motions necessary for mimicking an insect-like flapping-wing trajectory: sweeping (side to side), plunging (up and down), and pitching (angle of attack variation). Lift was measured via a force balance while the following kinematic parameters were varied: flapping frequency (f), angle of attack at mid-stroke (alpha(mid)), timing of pitch reversal with stroke reversal (rotation phase), stroke amplitude (Phi), and plunge amplitude (Theta). Results revealed that mean lift scaled with f(1.5) and varied proportionally with Theta. A pitch reversal advanced by up to 5 per cent of the flapping period relative to stroke reversal was found to maximize mean lift, and delayed pitch reversals were detrimental to mean lift. Of the parameters tested, mean lift was also maximized for alpha(mid) = 45 degrees and Theta = 8.6 degrees.