PIV investigation on airfoil with ice accretions and resulting performance degradation

An experimental study was conducted to investigate the effect of ice accretions on the aerodynamic characteristics of a 100 mm-chord NACA 0012 airfoil section. Four different configurations of the airfoil model were considered: clean profile and profile with glaze, rime and mixed ice-accretion. shapes. The considered shapes were derived from measurements performed at the NASA Lewis Icing Research Tunnel (IRT). Tests were performed in the closed test section of an open circuit calibration tunnel: the chord Reynolds number was about 200000. Velocity field was measured by means of PIV technique on the clean and mixed airfoils, whereas aerodynamic coefficients for all the different ice accretion shapes were measured as a function of airfoil incidence, by means of a three component balance. The experimental results show remarkable aerodynamic characteristics decay due to the simulated ice formation: glaze configuration shows worst performances with inversion of the lift-incidence curve and a dramatic increase of the drag coefficient. PIV measurements show large regions of separated flow even at low incidence and for moderate amount of ice (mixed shape): in fact, due to the low chord Reynolds number, no flow reattachment occurs downstream the separation.