The Effects of a Flexible, Flapping Airfoil on Power Extraction and Propulsive Efficiency: A Numerical Solution

Abstract

The use of pitching, plunging airfoils for both propulsion and power extraction in recent history has gained much interest due to its relatively high efficiencies at low Reynolds numbers. Chordwise airfoil flexibility has been shown to increase the efficiency of both flapping propulsion and power extraction, however research into the passive deformation of such an airfoil under aerodynamic load is minimal. A method was developed in order to allow the quasi two-dimensional testing of a pitching, plunging airfoil for both power extraction and propulsion. By utilising Computational Fluid Dynamics and Finite Element Analysis software, Fluid Structure Interaction was achieved enabling calculation of the aeroelastic deformation of a flapping cycle under both aerodynamic and inertial loads. It was found that for flapping wing propulsion, there is an exponential relationship between increases of propulsive efficiency and increasing airfoil flexibility.