Experimental and numerical validation of a Francis turbine draft tube designed for mitigation of pressure fluctuations

Arthur Favrel*, Tatsuya Irie, Yuya Ishii, Nak Joong Lee, Kazuyoshi Miyagawa

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review


This paper presents an experimental and numerical investigation of the internal flow in a Francis turbine draft tube previously designed for minimizing pressure fluctuations and energy losses in off-design conditions. The design of the draft tube geometry is based on an original approach combining Design of Experiments and steady/unsteady Computational Fluid Dynamics (CFD) simulations of the draft tube internal flow. The proposed method provides new insight on the influence of the draft tube geometry on the flow dynamic behaviour on one hand and enables the determination of a geometry promoting flow stability and hydraulic performance on another hand. CFD simulations of the internal flow in the final geometry showed promising results in terms of flow stability compared with the initial geometry designed by conventional CFD-aided methods. A reduced-scale model of the prototype machine featuring the final draft tube geometry is finally installed and tested in laboratory. Tests include performance and pressure fluctuations measurements over the complete operating range. The analysis of the results shows that the draft tube flow remains globally stable over the complete part-load range with pressure fluctuations amplitude lower than 1% of the net head. It is also shown that the dominant pressure component at the runner outlet in the draft tube cone is of synchronous nature. The physical mechanisms of excitation are finally highlighted by analysis of unsteady CFD simulation results.

Original languageEnglish
Article number012017
JournalIOP Conference Series: Earth and Environmental Science
Issue number1
Publication statusPublished - 2022
Event31st IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2022 - Trondheim, Norway
Duration: 2022 Jun 262022 Jul 1

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)


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