A simulation framework for rotorcraft ice accretion and shedding

In this work a novel three-dimensional simulation framework for modelling the safety critical problem of rotorcraft ice formation and shedding is presented. To enable an entirely three-dimensional framework, state-of-the-art numerical modelling techniques are adopted and the inter-dependency between the techniques is discussed. The numerical techniques introduced in this work include models to simulate the rotor flow-field, water droplet trajectories and impingement locations, phase change modelling during the ice accretion, and mesh deformation to account for the moving ice boundary. A set of benchmark test cases are initially used for preliminary validation of the icing framework. This allows for a comparison of the collection efficiency and ice shapes with high-quality experimental measurements. Icing wind tunnel tests conducted on the Spinning Rotor Blade (SRB-II) model rotor are used for an assessment of the numerical predictions specific to rotorcraft. Quantities used for comparisons include the ice thickness and shedding location. Numerical predictions are in good agreement with the measured data at all temperatures. Additionally, the outcome of influential parameters which directly impact rotor ice shapes are assessed. In particular, the model for the temperature profiles within the ice layer, and the centrifugally induced movement of the liquid film.