Introducing Gurney flap to Wells turbine blade and performance analysis with OpenFOAM

Abstract

A Gurney flap (GF) placed at pressure side of the trailing edge of an airfoil and perpendicular to the chord line enhances lift in aircraft wings, helicopter rotors, and wind turbines, etc. In this article, the GF concept was introduced for Wells turbine blade used to harvest wave energy with special consideration as the blades are having symmetric airfoil and faces bidirectional flow. Hence, the flap was extended to both pressure and suction sides of the trailing edge (TE) to maintain blade symmetry, and the turbine performance was evaluated using opensource computational fluid dynamics code OpenFOAM 4.0. Different GF-lengths (0.5–3% chord length) were considered, and the performance parameters such as non-dimensional torque, pressure drop and efficiency were evaluated. The GF blades produced a counter-rotating vortex pair behind the TE which modified the TE Kutta condition and increased the circulation and lift. In addition, the GF blades increased the blade loading and enhanced the torque generated. However, the increased pressure drop lead to decrement in efficiency.