Propeller tip-vortex cavitation and its broadband noise

Johan Bosschers

    Research output: ThesisPhD Thesis - Research external, graduation UT

    471 Downloads (Pure)

    Abstract

    Comfort on board has become an important aspect in the design of ships over the last decades, especially comfort for passengers on cruise vessels and for owners of yachts. Therefore, cavitation on propellers for these ships should be minimized, leaving often only a tip-vortex cavity. However, tip-vortex cavitation is known to be a cause of broadband pressure fluctuations on the hull above the propeller, typically in a frequency range from 30 to 100 Hz, which has led to vibration problems for some ships. Broadband noise of cavitation is also of relevance for the underwater radiated noise emitted by the ship, not only from the perspective of the acoustic signature of military ships, but also because of the impact of noise on fish and marine mammals.

    The objective of the present PhD thesis was to develop prediction methods for broadband noise, including hull-pressure fluctuations, by developed propeller tip-vortex cavitation. Fundamental aspects of a cavitating vortex were investigated for this purpose, aiming at understanding the mechanisms involved in the generation of broadband noise and the effect of viscosity. This has been achieved by theoretical and computational studies of the kinematics, dynamics, and acoustics of vortex cavitation and by the analysis of experimental data. An analytical as well as a semi-empirical formulation for the azimuthal velocity distribution of a cavitating vortex has been developed. The semi-empirical formulation describes available experimental data well. A dispersion relation has been derived that describes disturbances on the cavity interface of a columnar vortex cavity of infinite length. The relation is derived for potential flow but contains an ad-hoc correction for viscous effects. The wavenumber-frequency diagram of this relation shows acceptable agreement with available experimental data.

    The knowledge and formulations obtained were used for the development of a semi-empirical prediction method for the broadband noise by tip vortex cavitation of a propeller operating in a ship wake field. The formulations were also used to develop a novel methodology for model tests to correct for the Reynolds-number scale effect on the radius of the vortex-cavity and its broadband noise.
    Original languageEnglish
    Awarding Institution
    • University of Twente
    Supervisors/Advisors
    • Hoeijmakers, Hendrik Willem Marie, Supervisor
    Award date21 Sep 2018
    Place of PublicationEnschede
    Publisher
    Print ISBNs978-94-92679-52-9
    DOIs
    Publication statusPublished - 21 Sep 2018

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    propellers
    cavitation flow
    vortices
    ships
    broadband
    formulations
    cavities
    comfort
    marine mammals
    scale effect
    mammals
    potential flow
    passengers
    acoustics
    theses
    fishes
    predictions
    wakes
    vessels
    Reynolds number

    Cite this

    Bosschers, Johan. / Propeller tip-vortex cavitation and its broadband noise. Enschede : University of Twente, 2018. 224 p.
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    title = "Propeller tip-vortex cavitation and its broadband noise",
    abstract = "Comfort on board has become an important aspect in the design of ships over the last decades, especially comfort for passengers on cruise vessels and for owners of yachts. Therefore, cavitation on propellers for these ships should be minimized, leaving often only a tip-vortex cavity. However, tip-vortex cavitation is known to be a cause of broadband pressure fluctuations on the hull above the propeller, typically in a frequency range from 30 to 100 Hz, which has led to vibration problems for some ships. Broadband noise of cavitation is also of relevance for the underwater radiated noise emitted by the ship, not only from the perspective of the acoustic signature of military ships, but also because of the impact of noise on fish and marine mammals.The objective of the present PhD thesis was to develop prediction methods for broadband noise, including hull-pressure fluctuations, by developed propeller tip-vortex cavitation. Fundamental aspects of a cavitating vortex were investigated for this purpose, aiming at understanding the mechanisms involved in the generation of broadband noise and the effect of viscosity. This has been achieved by theoretical and computational studies of the kinematics, dynamics, and acoustics of vortex cavitation and by the analysis of experimental data. An analytical as well as a semi-empirical formulation for the azimuthal velocity distribution of a cavitating vortex has been developed. The semi-empirical formulation describes available experimental data well. A dispersion relation has been derived that describes disturbances on the cavity interface of a columnar vortex cavity of infinite length. The relation is derived for potential flow but contains an ad-hoc correction for viscous effects. The wavenumber-frequency diagram of this relation shows acceptable agreement with available experimental data.The knowledge and formulations obtained were used for the development of a semi-empirical prediction method for the broadband noise by tip vortex cavitation of a propeller operating in a ship wake field. The formulations were also used to develop a novel methodology for model tests to correct for the Reynolds-number scale effect on the radius of the vortex-cavity and its broadband noise.",
    author = "Johan Bosschers",
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    doi = "10.3990/1.9789492679529",
    language = "English",
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    Propeller tip-vortex cavitation and its broadband noise. / Bosschers, Johan.

    Enschede : University of Twente, 2018. 224 p.

    Research output: ThesisPhD Thesis - Research external, graduation UT

    TY - THES

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    AU - Bosschers, Johan

    PY - 2018/9/21

    Y1 - 2018/9/21

    N2 - Comfort on board has become an important aspect in the design of ships over the last decades, especially comfort for passengers on cruise vessels and for owners of yachts. Therefore, cavitation on propellers for these ships should be minimized, leaving often only a tip-vortex cavity. However, tip-vortex cavitation is known to be a cause of broadband pressure fluctuations on the hull above the propeller, typically in a frequency range from 30 to 100 Hz, which has led to vibration problems for some ships. Broadband noise of cavitation is also of relevance for the underwater radiated noise emitted by the ship, not only from the perspective of the acoustic signature of military ships, but also because of the impact of noise on fish and marine mammals.The objective of the present PhD thesis was to develop prediction methods for broadband noise, including hull-pressure fluctuations, by developed propeller tip-vortex cavitation. Fundamental aspects of a cavitating vortex were investigated for this purpose, aiming at understanding the mechanisms involved in the generation of broadband noise and the effect of viscosity. This has been achieved by theoretical and computational studies of the kinematics, dynamics, and acoustics of vortex cavitation and by the analysis of experimental data. An analytical as well as a semi-empirical formulation for the azimuthal velocity distribution of a cavitating vortex has been developed. The semi-empirical formulation describes available experimental data well. A dispersion relation has been derived that describes disturbances on the cavity interface of a columnar vortex cavity of infinite length. The relation is derived for potential flow but contains an ad-hoc correction for viscous effects. The wavenumber-frequency diagram of this relation shows acceptable agreement with available experimental data.The knowledge and formulations obtained were used for the development of a semi-empirical prediction method for the broadband noise by tip vortex cavitation of a propeller operating in a ship wake field. The formulations were also used to develop a novel methodology for model tests to correct for the Reynolds-number scale effect on the radius of the vortex-cavity and its broadband noise.

    AB - Comfort on board has become an important aspect in the design of ships over the last decades, especially comfort for passengers on cruise vessels and for owners of yachts. Therefore, cavitation on propellers for these ships should be minimized, leaving often only a tip-vortex cavity. However, tip-vortex cavitation is known to be a cause of broadband pressure fluctuations on the hull above the propeller, typically in a frequency range from 30 to 100 Hz, which has led to vibration problems for some ships. Broadband noise of cavitation is also of relevance for the underwater radiated noise emitted by the ship, not only from the perspective of the acoustic signature of military ships, but also because of the impact of noise on fish and marine mammals.The objective of the present PhD thesis was to develop prediction methods for broadband noise, including hull-pressure fluctuations, by developed propeller tip-vortex cavitation. Fundamental aspects of a cavitating vortex were investigated for this purpose, aiming at understanding the mechanisms involved in the generation of broadband noise and the effect of viscosity. This has been achieved by theoretical and computational studies of the kinematics, dynamics, and acoustics of vortex cavitation and by the analysis of experimental data. An analytical as well as a semi-empirical formulation for the azimuthal velocity distribution of a cavitating vortex has been developed. The semi-empirical formulation describes available experimental data well. A dispersion relation has been derived that describes disturbances on the cavity interface of a columnar vortex cavity of infinite length. The relation is derived for potential flow but contains an ad-hoc correction for viscous effects. The wavenumber-frequency diagram of this relation shows acceptable agreement with available experimental data.The knowledge and formulations obtained were used for the development of a semi-empirical prediction method for the broadband noise by tip vortex cavitation of a propeller operating in a ship wake field. The formulations were also used to develop a novel methodology for model tests to correct for the Reynolds-number scale effect on the radius of the vortex-cavity and its broadband noise.

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    DO - 10.3990/1.9789492679529

    M3 - PhD Thesis - Research external, graduation UT

    SN - 978-94-92679-52-9

    PB - University of Twente

    CY - Enschede

    ER -