An Investigation on the Lift Mechanism of Flapping-Wing Air Vehicle

Abstract

This paper deals with the aerodynamical problems of rigid flapping wing at low Reynolds numbers with emphasis on investigating the lift generation mechanism of simplified ornithopter. Theoretical analysis and Particle Image Velocimetry (PIV) were conducted to analyze and verify the lift generation conditions. The results revealed that the rigid flapping wing will generate lift under the conditions of both angle of attackαand free incoming flow velocityvwere not zero. With the wings flapped periodically, there were votexes formed, developed and shedding alternately. The calculation of curl demonstrated that the greater of flapping speed, the greater of curl. The statistic of circulation suggested that the circulation generation of flapping down was greater than that of flapping up, the circulation difference contributed to the lift generation. The difference of circulation will increase along with the angle of attackαin the circumstances of free stream velocityvand flapping speedπand flapping amplitudeΦmatched well.