Experimental investigation of aerodynamic characteristics of a 4-winged flapping

An experimental setup was developed to study the aerodynamic characteristics of a 4-winged flapping mechanism. In particular, we measured the variation of thrust and pitching moment throughout the flapping cycle. The latter allowed estimation of the variation of the center of pressure during flapping. Moreover, we utilized a hall-effect sensor to provide a signal when the wing reaches the end of its downstroke. Hence, in combination with kinematic analysis of the driving mechanism, the flapping waveform was estimated with a good accuracy. The light weight of the hall-effect sensor allowed estimation of the variation of the flapping angle during the cycle with minimal effects on the inertial properties and performance of the flapping mechanism. As such, we exploited this simultaneous measurement of the variations of thrust and flapping angle to study the interesting physics underlying the superb performance of this four-wined flapping system. In particular, we identified peaks in the thrust force with leading edge vortex translatory effects in the downstroke and clapping effects at the end of it. We also measured the averaged power consumption. From which we presented the variation of the flapping propulsive efficiency with the flapping frequency to determine the optimal frequency for operation of this mechanism.