Experimental and numerical investigation of the influence of roughness and turbulence on LUT airfoil performance

Vertical-axis wind turbines (VAWTs) have been widely used in urban environments, which contain dust and experience strong turbulence. However, airfoils for VAWTs in urban environments have received considerably less research attention than those for horizontal-axis wind turbines (HAWTs). In this study, the sensitivity of a new VAWT airfoil developed at the Lanzhou University of Technology (LUT) to roughness was investigated via a wind tunnel experiment. The results show that the LUT airfoil is less sensitive to roughness at a roughness height of < 0.35 mm. Moreover, the drag bucket of the LUT airfoil decreases with increasing roughness height. Furthermore, the loads on the LUT airfoil during dynamic stall were studied at different turbulence intensities using a numerical method at a tip-speed ratio of 2. Before the stall, the turbulence intensity did not considerably affect the normal or tangential force coefficients of the LUT airfoil. However, after the stall, the normal force coefficient varied obviously at low turbulence intensity. Moreover, as the turbulence intensity increased, the normal and tangential force coefficients decreased rapidly, particularly in the downwind region of the VAWT.