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A full-automated CFD mesh generation technique has been developed and implemented for 3-D aircraft icing simulations to permit robust 45-minute ice accretion simulations in support of icing certification campaigns. The changes in the shape of the aircraft surfaces due to accreting ice and their effects on the air and droplet flow are accounted for in a quasi-steady manner by subdividing the total icing time into sequential steps of shorter duration, updating the computational grid at each step. This “multi-shot” ice accretion approach requires robust and accurate grid re-meshing for it to be embedded in engineering design and analysis workflows. ANSYS FENSAP-ICE has been coupled to Fluent Meshing to take advantage of generic and highly automated surface displacement and mesh wrapping tools. A wide spectrum of geometries is supported, ranging from full-size aircraft to air data probes, turbomachinery components, rotors and propellers.

A 3D CFD methodology is presented to simulate ice build-up on propeller blades exposed to known icing conditions in flight, with automatic blade pitch variation at constant RPM to maintain the desired thrust. One blade of a six-blade propeller and a 70-passenger twin-engine turboprop are analyzed as stand-alone components in a multi-shot quasi-steady icing simulation. The thrust that must be generated by the propellers is obtained from the drag computed on the aircraft. The flight conditions are typical for a 70-passenger twin-engine turboprop in a holding pattern in Appendix C icing conditions: 190 kts at an altitude of 6,000 ft. The rotation rate remains constant at 850 rpm, a typical operating condition for this flight envelope.

A CFD simulation methodology for the inclusion of the post-impact trajectories of splashing/bouncing Supercooled Large Droplets (SLDs) and film detachment is introduced and validated. Several scenarios are tested to demonstrate how different parameters affect the simulations. Including re-injecting droplet flows due to splashing/bouncing and film detachment has a significant effect on the accuracy of the validations shown in the article. Validation results demonstrate very good agreement with the experimental data. This approach is then applied to a full-scale twin-engine turboprop to compute water impingement on the wings and the empennage.

A CFD simulation methodology is presented to evaluate the ice that sheds from rotating components. The shedding detection is handled by coupling the ice accretion and stress analysis solvers to periodically check for the propagation of crack fronts and possible detachment. A novel approach for crack propagation is highlighted where no change in mesh topology is required. The entire computation from flow to impingement, ice accretion and crack analysis only requires a single mesh. The accretion and stress module are validated individually with published data. The analysis is extended to demonstrate potential shedding scenarios on three complex industrially-relevant 3D cases: a helicopter blade, an engine fan blade and a turboprop propeller. The largest shed fragment will be analyzed in the context of FOD damage to neighboring aircraft/component surfaces.

A CFD simulation methodology is presented to calculate blockage due to ice crystal icing of the IGV passages of a gas turbine engine. The computational domain consists of six components and includes the nacelle, the full bypass and the air induction section up to the second stage of the low-pressure compressor. The model is of a geared turbofan with a fan that rotates at 4,100 rpm and a low-pressure stage that rotates at 8,000 rpm. The flight conditions are based on a cruising speed of Mach 0.67 in Appendix-D icing conditions with an ice crystal content is 4.24 g/m3. Crystal bouncing, and re-entrainment is considered in the calculations, along with variable relative humidity and crystal melting due to warmer temperatures within the engine core. Total time of icing is set to 20 seconds. The CFD airflow and ice crystal simulations are performed on the full 6-stage domain. The initial icing calculation determines which stage will be chosen for a more comprehensive analysis.

The importance of the variation of relative humidity across turbomachinery engine components for in-flight icing is shown by numerical analysis. A species transport equation for vapor has been added to the existing CFD methodology for the simulation of ice growth and water flow on engine components that are subject to ice crystal icing. This entire system couples several partial differential equations that consider heat and mass transfer between droplets, crystals and air, adding the cooling of the air due to particle evaporation to the icing simulation, increasing the accuracy of the evaporative heat fluxes on wetted walls. Three validation cases are presented for the new methodology: the first one compares with the numerical results of droplets traveling inside an icing tunnel with an existing evaporation model proposed by the National Research Council of Canada (NRC).