Dynamic stall control on a vertical axis wind turbine aerofoil using leading-edge rod

The installation of a small rod in front of the leading edge of the symmetrical aerofoil as a passive control approach was proposed to control the dynamic stall of the Darrieus vertical-axis wind turbine (DVAWT). The flows around original NACA 0018 aerofoil and that with a rod were extensively simulated by solving the unsteady Reynolds-averaged Navier-Stokes equations with an SST k-omega turbulent model to investigate the effect of the rod on the dynamic stall control of the aerofoils undergoing Darrieus pitching motions. Numerical simulation results reveal that the counter-rotating vortices shedding from the rod continuously transmit kinetic energy into the boundary layer of the aerofoils. This mechanism prevents the formation of dynamic stall vortex and eliminates the flow separation of the aerofoils at large angles of attack. Parameter studies show that the diameter of the rod and the gap between the rod and aerofoil play an important role in stall control and performance improvement of the aerofoil. With the aid of the leading-edge rod, up to 210.9% relative increment of average tangential force coefficient for oscillating aerofoil and 42.1% relative increment of power coefficient for a two-bladed DVAWT were achieved at a tip speed ratio of 2. (C) 2019 Elsevier Ltd. All rights reserved.