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This work presents the implementation and validation efforts of a 3D ice accretion solver for aeronautical applications, MESS3D, based on the advanced Messinger model. The solver is designed to deal with both liquid phase and ice crystal cloud conditions. In order to extend the Messinger model to 3D applications, an algorithm for the water run-back distribution on the surface was implemented, in place of an air flow stagnation line search algorithm, which is straightforward in 2D applications, but more complicated in 3D. The developed algorithm aims to distribute the run-back water in directions determined by air pressure gradients or shear forces. The data structure chosen for MESS3D allows high flexibility since it can manage the necessary input solutions on surface grids coming from both structured and unstructured solvers, regardless the number of edges per surface cells.

Recent aircraft incidents and accidents have highlighted the existence of icing cloud characteristics beyond the actual certification envelope defined by the JAR/FAR Appendix C, which accounts for an icing envelope comprising water droplets up to a diameter of 50 μm. The main concern is the presence of SLD (Supercooled Large Droplets), with droplet diameters well beyond 50 microns. In a previous European-funded project, EURICE, in-flight icing conditions and theoretical studies were performed to demonstrate the existence of SLD and to help characterize SLD clouds. Within the EXTICE project the problem of SLD simulation is addressed with both numerical and experimental tools is being addressed. In this paper the objectives and main achievements of the EXTICE project will be described.

In the present work, numerical results of ice accretion prediction on the UH-1H helicopter rotor blade with a NACA 0012 airfoil are reported. During the winter of 1982-83, the NASA Lewis Research Center and the US Army conducted a helicopter icing flight test (HIFT) program using a UH-1H aircraft at the Canadian National Research Council spray rig at Uplands Airport, Ottawa, Canada. From several hover icing flight conditions conducted in the HIFT program, a test case is selected to be evaluated with numerical analysis. The computation is performed at an airspeed of 4.6 m/s, ambient temperature of -19.0°C, liquid water content of 0.7 g/m3 and an exposure time of 3 minutes. In order to reproduce the experimental aerodynamic conditions the three-dimensional flow field is numerically computed. Both a two-dimensional and three-dimensional approach is followed to predict the ice shape.