Unsteady Pressure Distribution of a Flapping Wing Undergoing Root Flapping Motion with Elbow Joint at Different Reduced Frequencies

This paper reports on the result of wind tunnel test of a mechanical flapping wing undergoing pure flapping with elbow joint. The objective of this work is to investigate the effect of reduced frequency on the unsteady pressure distribution around a flapping wing cross section. A specially designed mechanical wing flapper with elbow joint was developed and tested. The data measured were the kinematics, airspeeds and pressure distribution around the outer wing cross section at three different reduced frequencies. The results revealed three distinct flow phenomena of attach flow, laminar separation bubble and dynamic stall occurring at the reduced frequencies tested. These flow characteristics are dependent on the instantaneous effective angle of attack of the wing during flapping.