Air-water flows in water engineering and hydraulic structures. Basic processes and metrology

Hydraulic researchers had been leading air-water flow studies until the mid-1950s. Since progresses have been dominated by multiphase flow experts despite the relevance of "white water" phenomena to hydraulic engineering. In this lecture the writer reviews the basic mechanisms of air entrainment: singular aeration and interfacial entrainment. The relevant instrumentation and data processing technique are detailed. Later recent progresses in unsteady flow measurements and in seawater are discussed.