Intrusive and non-intrusive two-phase air-water measurements on stepped spillways: A physical study

Self-aerated free-surface flow studies have a more recent history compared to classical fluid dynamics. Traditional velocimetry techniques are adversely affected by the presence of gas–liquid interfaces. In present study, detailed air-water measurements were performed in highly turbulent flow, and three approaches applied: (a) centreline dual-tip phase-detection needle probe at all step edges downstream inception location aeration; (b) Optical Flow (OF) data based upon ultra-high-speed video movies through left sidewall; (c) overlooking self-aerated direction normal pseudo-bottom formed staircase profile. The study was conducted steep channel stepped invert geometries tested. results highlighted both advantages limitations complementary metrologies flows with strong turbulence. delivered reliable interfacial velocity data, but form point measurements. sideview OF technique provided great level details cavity recirculation shear zone between mainstream cavity, unreliable for void fractions>0.30 only limited sidewall region. top view characterised surface field across entire chute width, highlighting occurrence three-dimensional patterns. One observed limitation requirements high frame rate (i.e. 10,000 fps or more) high-quality light source. Overall, these measurement better understanding physical behaviour multiphase on channels.