PIV of the aerodynamics of an airfoil subjected to icing

Wind turbines located in cold climates face several issues due to ice accretion. These include power losses, mechanical failure and changes in the aerodynamic behaviour. While the effect on symmetric airfoils and airfoils intended for aviation has been covered in the literature, airfoils designed for wind turbines have received limited attention. Therefore, particle image velocimetry experiments have been conducted to investigate the flow field over a NREL S826 airfoil, with different ice accretions at the leading edge. The three accretions represent different icing conditions, namely rime, glaze and mixed conditions. The mixed icing has a horn geometry, while the others have a streamlined geometry. Experiments were also conducted on the clean airfoil for comparison. Different angles of attack were used, ranging from -4deg to 16deg for all geometries. From the measurements, mean velocity, turbulent kinetic energy, mean vorticity and instantaneous swirl have been calculated. The results demonstrate how the separation bubble changes with angle of attack for the horn accretion. A separation bubble over the streamlined accretions at high angle of attack was also found. The shear layer between the recirculating region and the freestream are also described for all experimental cases.