Wind tunnel testing of the fish bone active camber morphing concept

Abstract

This work presents comparative experimental investigations into the aerodynamics of the recently proposed Fish Bone Active Camber morphing structure. This novel, biologically inspired concept consists of four main elements: a compliant skeletal core, a pre-tensioned elastomeric matrix composite skin, an antagonistic pair of tendons coupled to a non-backdriveable spooling pulley as the driving mechanism, and a non-morphing main spar. The Fish Bone Active Camber concept is capable of generating large changes in airfoil camber and is therefore proposed as a high-authority morphing solution for fixed-wing aircraft, helicopters, wind turbines, tidal stream turbines, and tilt-rotors. This testing compares a baseline airfoil employing a conventional trailing edge flap to a continuous morphing trailing edge using the Fish Bone Active Camber concept. Testing is performed in the low-speed wind tunnel at Swansea University over a range of camber deformations and angles of attack. Both approaches are capable of generating similar levels of lift coefficient; however, comparison of the drag results shows a significant reduction for the Fish Bone Active Camber geometry. While purely two-dimensional flow was not achieved due to restrictions of the tunnel, the two airfoils operated in similar flow environments, allowing for a direct comparison between the two. Over the range of angles of attack typically used in fixed and rotary wing applications, improvements in the maximum obtainable lift-to-drag ratio on the order of 20%–25% are shown.