This paper presents a novel level-set-based approach to model evolving boundary problems for in-flight ice accretion. No partial differential equations are solved as in the standard level-set formulation, but simple geometrical quantities are employed to provide an implicit discretization of the updated boundary. This method avoids mesh entanglements and grid intersections typical of algebraic and mesh deforming techniques, making it suitable for generating a body-fitted discretization of arbitrarily complex geometries as in-flight ice shapes, including the collision of separate ice fronts. Moreover, this paper presents a local ice thickness correction, which accounts for the body’s curvature, to conserve the prescribed iced mass locally. The verification includes ice accretion over an ellipse and a manufactured example to show the proposed strategy’s advantages and robustness compared to standard algebraic methods. Finally, the method is applied to ice accretion problems. A temporal and grid convergence study is presented for automatic multistep in-flight simulations over a NACA0012 airfoil in rime, glaze, and mixed ice conditions.

This paper presents an innovative approach to model evolving boundaries problems due to the accumulation or erosion of material over a surface, offering a robust alternative to standard algebraic methods. The strategy is based on the level-set method and it allows the local conservation of the prescribed mass material accounting for the curvature of the body. No partial differential equations are solved for the level-set function, but simple geometric quantities are used to provide an implicit discretization of the new updated boundary. The method is applied to body-fitted unstructured grids, that allow a good representation of arbitrarily complex geometries. Two multi-step in-flight ice accretion simulations over a NACA0012 are presented to show the feasibility and adaptability of the method, that can be also extended to three-dimensional applications.

This paper presents the Politecnico di Milano Icing Research Group's contribution to the 1 st AIAA Ice Prediction Workshop. A collection of two-and three-dimensional test cases to predict the collection efficiency and ice accretion are simulated using the PoliMIce ice accretion software suite. Test cases include the prediction of the collection efficiency on a three-elementairfoil and on a full-scale horizontal swept tail plane. Additionally, test cases for the simulation of ice shapes on a NACA23012 airfoil and on swept wings with varying degrees of sweep angle are assessed. The numerical predictions are evaluated and compared to high quality experimental measurements taken from the NASA Glenn Icing Research Tunnel. In general the numerical predictions compare favourably with the experimental measurements. Key droplet impingement characteristics including the collection efficiency peak and impingement limits are captured. Meanwhile distinctive ice features of rime and glaze ice regimes are depicted in the simulations. However, there remains scope for further improvement of models as highlighted by the more challenging test cases such as the three-element-airfoil and the test cases which produce glaze ice shapes with large horns.

<div class="section abstract"><div class="htmlview paragraph">This paper presents a novel fully-automatic remeshing procedure, based on the level-set method and Delaunay triangulation, to model three-dimensional boundary problems and generate a new conformal body-fitted mesh. The proposed methodology is applied to long-term in-flight ice accretion, which is characterized by the formation of extremely irregular ice shapes. Since ice accretion is coupled with the aerodynamic flow field, a multi-step procedure is implemented. The total icing exposure time is subdivided into smaller time steps, and at each time step a three-dimensional body-fitted mesh, suitable for the computation of the aerodynamic flow field around the updated geometry, is generated automatically. The methodology proposed can effectively deal with front intersections, as shown with a manufactured example. Numerical simulations over a NACA0012 swept wing both in rime and glaze conditions are compared with the experimentally measured ice shapes from the 1st AIAA Ice Prediction Workshop.</div></div>

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