Browse Publications Technical Papers 2019-01-2002
2019-06-10

Numerical Modelling of Primary and Secondary Effects of SLD Impingement 2019-01-2002

A CFD simulation methodology for the inclusion of the post-impact trajectories of bounced and splashed Supercooled Large Droplets (SLDs) for a full-scale twin-engine turboprop is presented. The impingement and re-entrainment of SLDs from the propeller is also included in the model to account for the change in LWC through the propeller disk, as well as the breakup and dispersion of droplets shed by the blades due to bouncing and water film run-off. The full aircraft is modeled to capture the asymmetric water impingement and ice coverage on the wings and the empennage, since both propellers are rotating in the same direction. Since the performance characteristics of twin-engine commercial turboprops are such that they operate most efficiently at flight levels where SLD encounters may occur, the goal of this article is to establish a 3D computational methodology to eventually enable a complete study of the impact of FAR 25 Appendix C and O on the IPS requirements for this class of airplanes. The Appendix O icing conditions used for the demonstration of the methodology are set for a turboprop in a typical holding pattern at 6,000 ft, 190 kts and 5˚ angle of attack. The air static temperature is 268˚K and the LWC 0.3 g/m3. Both freezing rain and freezing drizzle environments are considered for the MVD > 40-micron droplet distributions. The preliminary results for these flight conditions show that inclusion of the secondary impingement in the simulation accounts for an increased water catch by 4.3% on the wing, 13.5% on the vertical stabilizer, and 3.4% on the horizontal stabilizer.

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