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

R. Matsuzaka, T. Nakashima, Kazuyoshi Miyagawa

    Research output: Contribution to journalArticle

    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

    Fingerprint

    pipe
    cavitation
    experiment
    turbine
    vortex
    cavity
    oscillation
    simulation

    ASJC Scopus subject areas

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

    Cite this

    @article{8fe1965b624c4aa2ad7ddbaf9710ac21,
    title = "Study on flow instability in a diffuser with swirling flow under several conditions of pipe length and swirl intensity",
    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.",
    author = "R. Matsuzaka and T. Nakashima and Kazuyoshi Miyagawa",
    year = "2016",
    month = "12",
    day = "13",
    doi = "10.1088/1755-1315/49/8/082015",
    language = "English",
    volume = "49",
    journal = "IOP Conference Series: Earth and Environmental Science",
    issn = "1755-1307",
    publisher = "IOP Publishing Ltd.",
    number = "8",

    }

    TY - JOUR

    T1 - Study on flow instability in a diffuser with swirling flow under several conditions of pipe length and swirl intensity

    AU - Matsuzaka, R.

    AU - Nakashima, T.

    AU - Miyagawa, Kazuyoshi

    PY - 2016/12/13

    Y1 - 2016/12/13

    N2 - 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.

    AB - 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.

    UR - http://www.scopus.com/inward/record.url?scp=85012202870&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=85012202870&partnerID=8YFLogxK

    U2 - 10.1088/1755-1315/49/8/082015

    DO - 10.1088/1755-1315/49/8/082015

    M3 - Article

    AN - SCOPUS:85012202870

    VL - 49

    JO - IOP Conference Series: Earth and Environmental Science

    JF - IOP Conference Series: Earth and Environmental Science

    SN - 1755-1307

    IS - 8

    M1 - 082015

    ER -