Aeration and de-aeration in tailwater channels of Pelton turbines is mainly influenced by the flow coming down from the casing. Knowledge of the flow through the casing is also important for (1) the determination of the distance between the runner buckets and the surface of the two-phase (air-water) mixture in the channel and (2) an otptimum design of the casing.
Turbulence of the jets is supposed to play a mayor role in de-aeration in the tailwater channel. Turbulence is also an important input paramete for CFD calculations.
Basic data on jet velocities, turbulence and spatial distribution of flow are measured both on a model turbine and on a prototype machine (vertical, six-jet). Measurements are made using pressure probes. The interesting parametes will be derived by calibration from high-speed camera observations of falling jets.