Effect of Wing Twisting on Aerodynamic Performance of Flapping Wing System

Abstract

In this paper, a simple but effective design for implementing a negative wing twist in a beetle-mimicking wing system is presented. The effectiveness of the design in terms of force generation and power consumption is confirmed by both experiment and calculation. An unsteady blade-element-theory model is used to estimate the aerodynamic forces produced by two different wing kinematics of a flapping-wing system. The model was first validated with the measurement data and two three-dimensional computational-fluid-dynamics results from the literature. The difference between the estimated average lift and the measured lift is 5.6%, which proves that the unsteady blade-element-theory model provides reasonable aerodynamic force estimation. The time history of the current estimation is also close to the measured data and is in between the two computational-fluid-dynamics results. The forces generated by the flapping wings with and without wing twist are estimated using the unsteady blade-element theory to investigate effect of the wing twist on the force generation. The result shows that the flapping-wing system with wing twist produces a 9.5% larger average vertical force or thrust while consuming 37% less power than the flapping-wing system without wing twist. The measured thrust by the swing test also shows 13.2% increase for the flapping wing with wing twist. Thus, by the estimation and measurement, it is confirmed that the wing twist improves the thrust generation.