Experimental analysis of 3-D sweeping wings

Çakır, Hasan
The aim of this thesis is to modify the mechanism, which is capable of mimicking the insect flight and developed previously by the Aerospace Engineering Department, and to measure the forces and moments of three types of flapping wings fixed to this mechanism. The flapping wing design is a new research topic, comparably young area and can be the future for micro unmanned air vehicles. Time varying force and moment data obtained from the experiments conducted in water as part of this thesis can be used to determine which wing geometry can be chosen for different pitch and sweep angles. A sensor measuring even very small forces and moments simultaneously in 3 axis is employed in this mechanism. Before the experiments, various birds and mechanisms are investigated and a bird wing geometry has been chosen to compare its aerodynamic features with the other geometries. Furthermore, in order to improve the mechanism and to find out the best mechanism mimicking the hummingbird flight, various test setups was studied. A connector has been designed between the mechanism and the sensor in order to minimize errors. And also this connector let us measure the pitch angle precisely whereas the old mechanism was able to measure only an approximate pitch angle. Additionally a roller bearing has been located at the center of the gear in order to transfer the power efficiently. A program which is called as “Wing-Sim” is used to control motor drivers and wings. Totally, 21 cases have been performed with three type of wings whose names are Flat Plate, Hummingbird and Zimmermann. The period of each case is 10 seconds and every cases have 50 periods. The wings have approximately the same size with each other which are 26 cm span, 7.9 cm chord and 3 mm thickness. Moreover, experimental uncertainties associated with low level fluid dynamic force measurements are addressed in this study. A drastic increase in drag force is observed after 30º pitch angle while lift force is not changed. The most efficient wing is the Zimmermann with its high L/D ratios.