Aerodynamic analysis of bionic cylindrical rib-supporting wings in plunging and flapping motions

A simplified rectangular thin-wing model with a spanwise rib is proposed to investigate the influence of the front limb and fingers embedded in the bat membrane wing on aerodynamics. The leading edge rib-enhanced wing (LRW) and the middle rib-enhanced wing (MRW) have been studied numerically in two-dimensional plunging and three-dimensional flapping motions. It is found that the aerodynamic features of the plunging and flapping wings are similar, i.e., the spanwise cylindrical rib only affects the chordwise forces on the model wings and almost does not change the normal forces. In particular, the leading edge rib-supporting structure increases the thrust due to the large region of low pressure on the rib's head when the wing moves in moderate or large amplitudes. When the rib is placed far away from the leading edge, the influence decreases rapidly. Furthermore, the effects of spanwise rib-enhanced wing are independent of Reynolds number when it is greater than 1000. The present study can assist in the design of rib-enhanced wings for bionic flapping-wing air vehicles.