The GREENPEG project, which is funded by the European Commission Horizon 2020 ‘Climate action, environment, resource efficiency and raw materials’ programme, aims to develop multi-method exploration toolsets for the identification of European, buried, small-scale (0.01-5 million m3) pegmatite ore deposits of the Nb-Y-F (NYF) and Li-Cs-Ta (LCT) chemical types. The project is being coordinated by the Natural History Museum of the University of Oslo and involves three exploration services/mining operators, one geological survey, three consulting companies and five academic institutions from eight European countries.  The target raw materials are Li, high-purity quartz for silica and metallic Si, ceramic feldspar, REE, Ta, Be and Cs, which are naturally concentrated in granitic pegmatites. Silicon and Li are two of the most sought-after green technology metals as they are essential for photovoltaics and Li-ion batteries for electric cars, respectively. GREENPEG will change the focus of exploration strategies from large-volume towards small-volume, high quality ores and overcome the lack of exploration technologies for pegmatite ore deposits by developing toolsets tailored to these ore types. This contribution focuses on the methods applied in the GREENPEG project and as such provides a potential pathway towards the ’Green Stone Age’ from the perspective of pegmatite-sourced minerals.

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.

The safety of rotorcraft operating in cold environments is jeopardised by the possibility of ice accretion on the rotor blades. Eventually, ice can shed from the blade due to the high centrifugal forces and impact other parts of the rotorcraft or unbalance the rotor. To establish the shedding time and location for rotorcraft, a robust and efficent numerical multi-step icing simulations tool is presented here for predicting the shedding phenomenon. A volume-mesh based approach is used to allow for representing the ice shape. In order to increase the robustness of the method, an interpolation procedure is implemented which establishes the possible occurrence of the shedding event and restricts the search domain. Ice shapes along the blades are computed by means of two-dimensional ice accretion simulations: ice shapes are then interpolated over the blade span. Numerical results compares fairly well, in terms of shedding time and location, to the experimental ones obtained in the AERTS test facility, thus demonstrating the soundness of the present approach.

<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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