Figure 7.

The shear strain at the quarter span along the mid-chord ɛ_xy versus time, t, for flapping alone (a,d) and flapping and rotating with periodic angular velocity (b,e). The additional subscripts of ɛ_xy are F for flapping alone and F&R for flapping and rotating. Time domain results for a time-average taken over 10 rotation cycles are shown for computational (a–b) and experimental (d–e) models. Shading denotes standard deviation. Frequency domain results of the difference in amplitude of the FFTs of ɛ_xy for flapping and rotating compared to flapping alone for the computational (c) and experimental (f) models. Note the peaks at the flapping frequency of 25 Hz, plus and minus the rotation frequency of 3 Hz, and their harmonics. (Online version in colour.)