Simulation of SLD Impingement on a High-Lift Airfoil

Computational water droplet impingement results for a high-lift airfoil, consisting of a flap, main and slat elements, are presented and are compared with experimental data. Droplet breakup, splashing and rebound models were used to evaluate the effects of large droplet dynamics on the impingement results. Droplet breakup effects were simulated using the Taylor Analogy Breakup (TAB) model. Large droplet splash effects were simulated with an empirical model developed at Wichita State University. A droplet rebound model is presented for computing droplet rebound mass, size, velocity and angle after a splash event. The three models were implemented into a droplet trajectory code to compute the droplet impingement distributions in the airfoil. The analyses were performed with cloud MVDs of 11, 21 and 92 µm, and α = 0° and 4°. Comparison of the simulated results with experimental measurements showed that large droplet dynamics has a significant effect on the impingement distributions in SLD clouds compared to the Appendix C clouds. Droplet splashing occurred in all three elements and droplet re-impingement was observed on the main and flap elements. Slight disagreements between experimental and simulated results were found in areas of the airfoil that experienced both droplet splashing and reimpingement. This was due to the sensitivity of the rebound model which has only been validated qualitatively due to the lack of quantitative data. In general, the breakup, splashing and rebound model models performed well as evidenced by the good agreement between simulated and experimental impingement distributions.