Open AccessStereo-PIV investigation of the unsteady flow in the draft tube of a model hydro turbine
Author(s) -
Ivan V. Litvinov,
D. K. Sharaborin,
С. И. Шторк,
В. М. Дулин,
Sergey Alekseenko,
Kilian Oberleithner
Publication year - 2021
Publication title -
international symposium on particle image velocimetry.
Language(s) - English
Resource type - Journals
ISSN - 2769-7576
DOI - 10.18409/ispiv.v1i1.102
Subject(s) - draft tube , mechanics , vortex , turbine , flow (mathematics) , instability , physics , tube (container) , francis turbine , rotation (mathematics) , water turbine , geology , engineering , mechanical engineering , mathematics , thermodynamics , geometry
Varying the generator load of a hydro turbine results in short-term changes in the rotation frequency of the runner, leading inevitably to flow instability and strong flow swirling behind the turbine. This may lead to the formation of unsteady flow regimes featured by vortex instability of the swirling flow behind the runner, known as the precessing vortex core (PVC) Dorfler et al. (2012). This effect causes dangerous periodic pressure pulsations that propagate throughout the water column in the draft tube. The present study reports on stereo PIV measurements of the air flow field inside a transparent draft tube of a model hydro turbine for a wide range of operation conditions. The research is focused on the time-averaged flow properties (mean velocity field and the second-order moments of velocity fluctuations), pressure pulsations and coherent flow structures in the velocity field.