Unsteady numerical simulation of the icing process on oscillating airfoils

Rotor blade icing degrades aerodynamic characteristics, affecting helicopter flight safety. The rotor blades under the forward flight state of a helicopter perform periodic variable pitch motion, which is the oscillation process of the rotor airfoil. Compared to fixed-wing icing, the unsteady characteristic of oscillating airfoil icing is a complex problem. To address this, numerical simulations of the unsteady airflow field in an unstructured overlapping grid system and the impact characteristics of supercooled water droplets based on the Euler method are carried out. An improved unsteady icing calculation method based on the Myers icing model is proposed. A dynamic mesh generation method based on Delaunay graph mapping and radial basis function is developed for multi-stage icing simulation. A set of unsteady numerical simulation methods for oscillating airfoil icing is synthesized. Accordingly, icing wind tunnel test conditions are numerically simulated, and the predicted ice shape is compared to that of the icing wind tunnel test. The data on macroscopic characteristics, including icing limit, ice angle position, and maximum thickness of icing, are in good agreement, verifying the accuracy and reliability of the calculation method. Furthermore, the influence of oscillation amplitude, oscillation frequency, and icing temperature on the icing process of oscillating airfoils is investigated. The icing limit of the airfoil pitching motion is higher than that of static airfoil icing. The oscillation frequency and amplitude of the airfoil pitching motion have a lesser effect on rime ice than on glaze ice. The glaze ice angle feature gradually disappears with increased frequency and amplitude, making the ice shape smooth.