Comparison of instrumentation in high-velocity air-water flows

Dr Michael Pfister (Left) and Dr Stefan Felder (Right) investigating high-velocity air-water flows on a stepped spillwayWRL academic Dr Stefan Felder recently returned from a visit of the Laboratory of Hydraulic Constructions (LCH) at EPFL Lausanne, Switzerland where he collaborated with Dr Michael Pfister (LCH, EPFL) on the measurement of high-velocity air-water flows on a stepped spillway. In this project, Dr Felder and Dr Pfister compared the performance of the two commonly used air-water flow instrumentation, i.e. conductivity probes and optical fibre probes, in the same experimental channel, under identical flow conditions, and with the same data acquisition and analysis systems.

Dr Felder and Dr Pfister combined their expertise in a novel comparative study of the two types of air-water flow instrumentation to provide an important answer for the hydraulic engineering community.


While the optical fibre probe is commercially available, the conductivity probe as well as the acquisition system and data analysis software were designed by Dr Felder at WRL.

Conductivity and optical fibre probes are used in measurements of air concentrations and flow velocities in air-water flows such as spillways, drop structures and hydraulic jumps. In the past decades, many laboratory studies of aerated flows have been conducted providing data for validation of numerical models, for design guidelines of hydraulic structures and for fundamental understanding of air-water flows. Interestingly these experimental studies have been performed either with optical fibre or conductivity probes depending on the preferences of the hydraulic researchers. To date the effects of instrumentation on the measurements of high-velocity air-water flows are unknown.

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