Instrumentation for Aerated Flow on Spillways

Instruments that have been used for measuring air concentration and velocities in self-aerated flow are examined. For air concentration measurements it is shown that the conductivity probe is satisfactory. For the velocity measurement the concentration measurements together with a pressure cell measuring the total head was attempted but the measurements were difficult to interpret. A correlation probe which detected the air water interface as it passed between two needles proved satisfactory for mean velocity measurements and the signal from a single resistance probe was used to estimate the bubble size. All of the probes were tested in the laboratory and on Aviemore spillway and based on this experience suggestions are made for future instruments.