Pereira, N. H. C.; Borges, J. E.; Matos, J. and Frizell, K.. 2007. "Developing a Combined Air Concentration and Velocity Probe for Measuring in Air-Water Jets". Bureau of Reclamation, Report Number PAP-969.
Abstract: Air-water flows occur in numerous types of hydraulic structures, as well as in hydraulic machinery like the Pelton and the Cross-Flow turbines. Due to the complexity inherent to the analytical and numerical study of highly turbulent air-water flows, experimental research has played a major role in the last decades, with the notable development of instrumentation techniques for measuring local air concentration and velocity, such as the electrical conductivity probes, fiber-optical probes and back-flushing Pitot tubes along with electrical conductivity probes. However, the application of these instruments is limited to situations where only a main flow direction exists which is known before the data acquisition. One example where such a priori knowledge does not exist is the flow inside and around the rotor of a Cross-Flow turbine. In order to perform the simultaneous measurement of the magnitude and direction of the velocity vector for application to Cross-Flow turbines a three-hole probe with back-flushing, combined with an electrical conductivity probe, has been developed in the Laboratory of Turbo-Machinery of the Department of Mechanical Engineering of the Technical University of Lisbon, in cooperation with the Water Resources Research Laboratory of the Bureau of Reclamation, USA. In this paper, the instrument development and calibration will be discussed, with particular emphasis on the air concentration measurements.
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