Experimental Estimation of the Rotary Damping Coefficients of a Pliant Wing

This paper describes the experimental estimation of the rotary-damping coefficients of micro air vehicle (MAV) wings using a novel system for dynamic wind-tunnel testing. Two geometrically identical Zimmerman wings are used, one rigid and one flexible. The flexible wing consists of a perimeter-reinforced latex membrane with three levels of prestrain. A two-degrees-of-freedom motion rig permits the control of the two individual components of the rotary-damping moment. A modern design of experiments methodology was used to elucidate the correlation between the wings' elastic membrane prestrain state and the aerodynamic characteristics. For the flexible wing, elastic deformations are measured using visual image correlation and evaluated using a dimensionless parameter. The resulting aerodynamic model compares well with static reference data. The presence of dynamic changes in the angle of attack or pitch angle has a significant effect on the response of the rigid and flexible MA V wings, particularly on the pitching moment coefficient. At the current levels of the dimensionless membrane wing elastic prestrain, the pretension strain did not exhibit any correlation with the rotary-damping moment coefficients, whereas the pretension strain level does appear as a factor in the rotary-damping drag coefficient.