Preliminary Measurements of the Radial Velocity in the Francis-99 Draft Tube Cone

Abstract

Two-dimensional particle image velocimetry (PIV) measurements in the draft tube cone of the Francis-99 model have been performed to complete the actual experimental data set with radial velocity data. The velocity profiles obtained presented some variation, which reason has not yet been identified. The presented results are therefore presented as preliminary until the reason is assessed. The axial velocity profiles corroborate well with the ones previously measured with laser Doppler velocimetry (LDV) for all operating points investigated. The radial velocity measured is small in magnitude for all operating points compared to the axial velocity. A gyroscopic effect induced by the swirl leaving the runner and the draft tube bend seems to induce an asymmetry in the draft tube cone.