Interfacial aeration and bubble count rate distributions in a supercritical flow past a backward-facing step

An example of high-velocity open channel flows is a supercritical flow past an abrupt drop. In such a geometry, the basic air–water flow properties were measured, including distributions of void fraction and bubble count rate, and local air and water chord size distributions, at and downstream of the backward-facing step. The bubble count rate distributions were compared with a conceptual model of streamwise distribution of air and water chords which yields a quasi-parabolic relationship between bubble count rate and void fraction. The proposed model was an attempt to explain the experimental relationship between bubble count rate and void fraction, rather a meticulous breakdown of the complex air–water structure.