Full-field three-dimensional measurements of dynamic ice accretion process based on multi-laser sheet scanning and polarization imaging

Aircraft icing can significantly affect aerodynamics and flight mechanics, giving rise to a serious risk for flight safety. Accordingly, a clear understanding of the dynamic ice accretion process is of crucial importance. In this study, a multi-laser sheet scanning approach combined with polarization imaging is developed to achieve the time-resolved full-field three-dimensional (3D) ice accretion shape measurements. By controlling two laser sheets to scan across the upper and lower airfoil from different perspectives simultaneously, the entire geometric shape of the ice accretion on the airfoil was covered completely. To solve the influence of stray and transmitted light for the shape measurements of the ice accretion, especially the glaze ice, two polarized cameras were used to capture the laser sheet scanning images in different perspectives, where the projected laser lines on the ice accretion were modulated to different intensities in different polarizations. By synthesizing all polarized sub-images, high-modulation laser line images could be formed, and thus accurate laser line extraction and reconstruction were finally achieved. The proposed approach is demonstrated in the large-scale icing wind tunnel tests of a National Advisory Committee for Aeronautics 0012 airfoil model, while the full-field temporal evolution of the rime, mixed, and glaze ice accretion shapes on the leading edge of the airfoil model was obtained successfully throughout the tests.