Study on flow instability in a diffuser with swirling flow under several conditions of pipe length and swirl intensity

R. Matsuzaka, T. Nakashima, K. Miyagawa

Research output: Contribution to journalConference article

Abstract

A swirling flow in a diffuser such as a draft tube of a hydro turbine may induce the flow instabilities accompanied by pressure fluctuations known as vortex rope behaviour and cavitation surge. Cavitation surge is the self-excited oscillation, which induces the large flow rate fluctuation that results from the change of the cavity volume. In this research, the investigation of the effect of the pipe length and the swirl intensity on the flow instabilities in a diffuser was performed by experiments and numerical analyses using the draft tube component experimental facility. The length of the pipe was modified by up to about 25 times as long as the diameter of the throat in order to validate the one-dimensional analyses. In addition, the swirl intensity was changed by replacing another swirl generator. The frequency of cavitation surge was changed with regard to the swirl intensity as the one-dimensional analyses in the previous study has predicted it. Unsteady numerical simulations of the swirling flow with cavitation in the diffuser was performed. The results of experiments and numerical analyses correspond qualitatively with the result of the one-dimensional analyses, which suggested that the coupling with the experiments, CFD analyses and the one-dimensional analyses is the more effective way in order to predict the flow instabilities in the diffuser.

Original languageEnglish
Article number082015
JournalIOP Conference Series: Earth and Environmental Science
Volume49
Issue number8
DOIs
Publication statusPublished - 2016 Dec 13
Event28th IAHR Symposium on Hydraulic Machinery and Systems, IAHR 2016 - Grenoble, France
Duration: 2016 Jul 42016 Jul 8

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ASJC Scopus subject areas

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

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