A Third-generation In-flight Icing Code: FENSAP-ICE-Unsteady 2007-01-3339

Ice accretion is a purely unsteady phenomenon that is presently approximated by most icing codes using quasi-steady modeling. The accuracy of ice prediction is thus directly related to the prescribed time step, or the time span during which the impact of ice growth on both flow and droplets can be neglected. Such approximation is removed by FENSAP-ICE-Unsteady which fully couples in time a diphasic flow (interacting air and droplet particles) with ice accretion. The two-phase flow is solved using the Navier-Stokes and Eulerian droplet equations, while the water film characteristics and ice shape are obtained from the conservation of mass and energy within a thin film layer. The iced surface being constantly displaced in time, Arbitrary Lagrangian-Eulerian terms are added to the governing equations to account for mesh movement. For rime ice, numerical results show that full unsteady modeling improves the accuracy of ice prediction when compared to one-shot ice accretion. The applicability of the icing model for predicting glaze ice accretion is also demonstrated.