Numerical Simulation of In-Flight Icing by a Multi-step Level-Set Method

Simulation of long-term in-flight ice accretion requires accounting for the feedback of the growing ice on the aerodynamics and particles’ impingement. This interaction is achieved by loosely coupling the flow and particles’ solvers to the ice accretion code in the simulation procedure. A quasi-steady approximation is made leveraging the different time scales at play: the total exposure time is subdivided into many smaller instants, after which the aerodynamics and collection efficiency are recomputed. This simulation approach allows better predictions of long-term ice accretion than the single-shot or the predictor-corrector approaches, at the expense of longer simulation times and some challenging technical difficulties. The multi-step approach’s main challenge is tracking the evolving air-ice interface and generating a volume-conforming grid to perform the required computation. This chapter reviews different approaches to model evolving boundary problems and highlights their main limitations when applied to in-flight icing simulations. Then, we present an innovative level-set-based approach to model the complex morphology of the accreting ice. Local conservation of the prescribed iced mass is enforced by accounting for the body’s curvature. Multi-step in-flight ice accretion simulations in rime and glace ice conditions over a NACA0012 wing are finally presented, proving the method’s robustness and adaptability.