College of Aeronautical Engineering, National University of Sciences and Technology, Islamabad, Pakistan
University of Southampton, Southampton, UK
Performance of a semi-active flapping foil flow energy harvester, coupled with a piezoelectric transducer has been analyzed in this work. The airfoil is mounted on a spring, damper and piezoelectric transducer arrangement in its translational mode. External excitation is imparted in pitch mode and system is allowed to oscillate in its translational mode as a result of unsteady fluid forces. A piezoelectric transducer is used as an electrical power converter. Flow around moving airfoil surface is solved on a meshfree nodal cloud using Radial Basis Function in Finite Difference Mode (RBF-FD). Fourth order Runge-Kutta Method is used for time marching solution of solid equations. Before the solution of complex Fluid-Structure Interaction problem, a parametric study is proposed to identify the values of kinematic, mechanical and geometric variables which could offer an improved energy harvesting performance. For this purpose, the problem is modelled as a coupled electromechanical system using Lagrange energy equations. Airfoil lift and pitching moment are formulated through Theodorson’s two dimensional thin-plate model and a parametric analysis is conducted to work out the optimized values of pivot location, pitch amplitude, spring stiffness and damping constant. The subsequent computational analysis resulted in an enhanced performance compared to the potential flow model with an efficiency of up to 27% based on total power extraction through the flow. Higher efficiency is obtained when the pitch axis is located aft of mid chord. However, this setting does not correspond to the maximum power output. Interestingly, power is maximized at much lower efficiency values.