Influence of a boundary on the development of a propeller wash

Harold T. Johnston, Gerard A. Hamill, Paul R. Wilson, Donal Ryan

    Research output: Contribution to journalArticle

    12 Citations (Scopus)

    Abstract

    When vessels operate within harbours or over a density interface in an estuary, the seabed or interface may be close to the tip of the propeller blades. The presence of this boundary will have an effect on the propeller wash and this can affect the erosion of the boundary. The influence of such a boundary on the characteristics of a propeller wash was studied in experiments using a horizontal fixed boundary to confine a propeller jet. Detailed velocity measurements within the jet were obtained using a 3D Particle Image Velocimetry (PIV) system. The bottom stream of a propeller jet was found to expand at a faster rate due to the reduction in pressure beneath the jet caused by the suppression of the replacement fluid. The boundary was found to significantly increase the axial velocities close to it, and reduce the rate of decay of the maximum axial velocity due to the confinement, reducing the height of the jet. Three zones within the propeller wash were identified, the first being before the jet impacted the boundary, the second in which the boundary layer developed at the fixed boundary, followed by a fully developed boundary layer region. Predictive equations to estimate the influence of the boundary have been developed and are presented.
    Original languageEnglish
    Pages (from-to)50-55
    Number of pages6
    JournalOcean Engineering
    Volume61
    Issue numbernull
    DOIs
    Publication statusPublished - 15 Mar 2013

    Fingerprint

    Propellers
    Velocity measurement
    Boundary layers
    Estuaries
    Ports and harbors
    Erosion
    Fluids
    Experiments

    Keywords

    • Propeller wash, harbours, berths, scour design

    Cite this

    Johnston, Harold T. ; Hamill, Gerard A. ; Wilson, Paul R. ; Ryan, Donal. / Influence of a boundary on the development of a propeller wash. In: Ocean Engineering. 2013 ; Vol. 61, No. null. pp. 50-55.
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    abstract = "When vessels operate within harbours or over a density interface in an estuary, the seabed or interface may be close to the tip of the propeller blades. The presence of this boundary will have an effect on the propeller wash and this can affect the erosion of the boundary. The influence of such a boundary on the characteristics of a propeller wash was studied in experiments using a horizontal fixed boundary to confine a propeller jet. Detailed velocity measurements within the jet were obtained using a 3D Particle Image Velocimetry (PIV) system. The bottom stream of a propeller jet was found to expand at a faster rate due to the reduction in pressure beneath the jet caused by the suppression of the replacement fluid. The boundary was found to significantly increase the axial velocities close to it, and reduce the rate of decay of the maximum axial velocity due to the confinement, reducing the height of the jet. Three zones within the propeller wash were identified, the first being before the jet impacted the boundary, the second in which the boundary layer developed at the fixed boundary, followed by a fully developed boundary layer region. Predictive equations to estimate the influence of the boundary have been developed and are presented.",
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    Influence of a boundary on the development of a propeller wash. / Johnston, Harold T.; Hamill, Gerard A.; Wilson, Paul R.; Ryan, Donal.

    In: Ocean Engineering, Vol. 61, No. null, 15.03.2013, p. 50-55.

    Research output: Contribution to journalArticle

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    T1 - Influence of a boundary on the development of a propeller wash

    AU - Johnston, Harold T.

    AU - Hamill, Gerard A.

    AU - Wilson, Paul R.

    AU - Ryan, Donal

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    AB - When vessels operate within harbours or over a density interface in an estuary, the seabed or interface may be close to the tip of the propeller blades. The presence of this boundary will have an effect on the propeller wash and this can affect the erosion of the boundary. The influence of such a boundary on the characteristics of a propeller wash was studied in experiments using a horizontal fixed boundary to confine a propeller jet. Detailed velocity measurements within the jet were obtained using a 3D Particle Image Velocimetry (PIV) system. The bottom stream of a propeller jet was found to expand at a faster rate due to the reduction in pressure beneath the jet caused by the suppression of the replacement fluid. The boundary was found to significantly increase the axial velocities close to it, and reduce the rate of decay of the maximum axial velocity due to the confinement, reducing the height of the jet. Three zones within the propeller wash were identified, the first being before the jet impacted the boundary, the second in which the boundary layer developed at the fixed boundary, followed by a fully developed boundary layer region. Predictive equations to estimate the influence of the boundary have been developed and are presented.

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