Wind tunnel testing of the fish bone active camber morphing concept

This work presents experimental investigations into the aerodynamic properties of the recently proposed Fish Bone Active Camber (FishBAC) morphing structure. This novel, biologically inspired, concept consists of four main elements; a compliant skeletal core, a pre-tensioned elastomeric matrix composite compliant skin, an antagonistic pair of tendons coupled to a non-backdriveable spooling pulley as the driving mechanism, and a non-morphing main spar. The FishBAC concept is capable of generating large changes in airfoil camber and is therefore proposed as a large authority, continuously variable camber solution for fixed wing aircraft, helicopters, wind turbines, tidal stream turbines, and tiltrotors. To allow for consideration of the aerodynamic performance of this concept relative to existing technology, a comparison is made between a NACA 0012 baseline airfoil with a plain trailing edge flap and the same baseline airfoil with a continuous morphing trailing edge using the FishBAC 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 found to be able to generate similar levels of lift coefficient, however comparison of the drag results shows a significant reduction for the FishBAC geometry. Over the range of angles of attack typically used in fixed and rotary wing applications, improvements in lift efficiency on the order of 25% are realized.