Potential of performance improvement of a modified Wells turbine using passive control for wave energy conversion

Wells turbine is widely used to convert wave energy into mechanical energy, although it suffers from a narrow operating range, low power output, and low efficiency. The study of the effect of Gurney flap geometry and Reynolds number on the performance of a Wells turbine is considered as an innovative work due to the research gap in this area. This work investigates the effect of a circular cavity in a rectangular Gurney flap, the cavity geometries, Gurney flap geometries, and finally a Reynolds number on the Wells turbine performance to increase the output power produced by the Wells turbine. The blade lift coefficient can be increased by modifying the Kutta condition using a Gurney flap at the trailing edge. To evaluate Wells turbine performance, 3D incompressible Reynolds-Averaged Navier-Stokes equations are numerically solved. The SST k-ω turbulence model is utilized to solve the flow field through the turbine, and the final result is validated using previous experimental and numerical studies to ensure that the computational model simulates the Wells turbine accurately. The current study emphasized that a circular cavity in a rectangular Gurney flap achieved the highest increase in the average torque coefficient, which is 27.58% compared with the conventional Wells turbine, so this flap is considered the best flap that has been studied. Furthermore, increasing Reynolds number delay stall inception and enhance torque coefficient, total pressure loss coefficient, and efficiency of Wells turbine with the conventional and flapped blades.