Supplementary Material

The present supplementary material provides extended results and insights into air-water flow properties that further support the findings of the study. While these supplementary details may be of particular interest to a more specialized subset of readers, they are presented to enhance the depth of the analysis. The supplementary material includes a discussion on self-similarity of void fraction profiles, the development of the maximum interface frequencies and of the shear velocities along the tunnel chute, representative interface velocity vertical profiles, as well as the influence of wall roughness on chord size distributions.