An experimental investigation of transient ice accretion process on a high-lift airfoil model for UAV applications

An experimental study is performed to investigate the transient ice accretion process along the surface of a high-lift, S1223 airfoil model, and the icing-induced aerodynamic performance degradation. The UAV airfoil model was exposed to typically glaze and rime icing conditions encountered by UAVs flying in low-altitude airspace. While the rime ice accretion was found to conform with the original profile of the UAV airfoil model well in general, substantial “feather-like” ice roughness elements were observed to grow rapidly over both the suction-side and pressure-side surfaces near the airfoil leading edge. The glaze ice accretion process was featured by obvious wind-driven water runback to transport the unfrozen water mass from the airfoil frontal surface to further downstream locations, causing the formation of complex rivulet-shaped ice structures and growth of ice “horns” along the leading edge and “finger-liked icicles” near the trailing edge. The aerodynamic performance of the UAV airfoil was found to degrade continuously with the increasing ice accretion time. The ice accretion over a period of 463 s was found to reduce UAV endurance from 18% to 46 % and diminish the UAV flying range by 13 % to 40 %, depending on the nature of ice accreted. The acquired ice accretion images were coordinated with the aerodynamic force measurements to gain further insight into the underlying physics for a better understanding of the UAV inflight icing phenomena.