Numerical and experimental studies of a morphing airfoil with trailing edge high-frequency flapping

Abstract

The aerodynamic performance of a morphing airfoil is numerically and experimentally investigated. The morphing airfoil is designed based on macro fiber composites, capable of trailing edge flapping during 10–90 Hz with a maximum amplitude of 0.55 mm. A numerical model with flexible deformation walls based on the experiment is established to precisely restore the actual dynamic morphing instead of segmental deformation to explore the transient aerodynamic performance of high-frequency flapping. The drag coefficient is reduced by 2.07% at the flapping frequency (ff) of 37.5 Hz compared with the rigid airfoil, while the drag coefficient and the lift coefficient increase by 4.8% and 5.8% for ff at 600 Hz. The vortex is broken up by flapping, and the corresponding position has been forwarded to the tail. Dynamic mode decomposition shows that the wing's flapping dominates the second mode and the high-frequency vortex has changed to low-frequency. The energy of higher modes is transferred to lower-order modes that the first mode's power has risen sharply from 49.29% of the rigid airfoil to 91.83%. In the wind tunnel experiment, the lift and drag forces are increased by 1.88% and 0.77% at the flapping frequency of 40 Hz, respectively. Furthermore, the lift force frequency is locked by flapping and changes from 124.9 Hz of the rigid airfoil to the flapping frequency, consistent with the computational fluid dynamics results. The research has provided a solution to reduce the drag force and increase the lift force of the aircraft by the trailing edge flapping.