Numerical Simulation of In-Flight Icing of Rotorcraft

When a rotorcraft operates in highly unsteady aerodynamic conditions in-flight icing simulation techniques based on quasi-steady assumptions are limited in accurately simulating ice accretion. In contrast, the application of an unsteady solver requires impractical computation resources to consider both the periodic motions of rotor blades and the gradual deformation of ice shape. Thus, the prediction of ice accretion on rotorcraft is challenging, considering the effect of unsteadiness while maintaining computation efficiency at a practical level. This chapter reviews the general aspects of rotorcraft icing and introduces up-to-date computational methods, such as quasi-steady numerical methods or actuator surface methods. Subsequently, the chapter introduces a 3-D quasi-unsteady approach, which combines an unsteady framework for airflow, droplet impingement, and ice accretion with a multi-shot ice shape generation method. Comparative results of the 2-D oscillating airfoil and 3-D rotorcraft icing simulation are presented to demonstrate the effect of aerodynamic unsteadiness on rotorcraft icing. The numerical issues while handling the rotorcraft icing simulation are described, offering a computational approach with greater predictive capabilities for rotorcraft icing.