Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

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    • Tianming Zhang
    • Wei-Haur Lam
    • Yonggang Cui
    • Jinxin Jang
    • Chong Sun
    • Jianhua Guo
    • Yanbo Ma
    • Shuguang Wang
    • Su Shuing Lam
    • Gerard Hamill

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    The scouring by a tidal turbine is investigated by using a joint theoretical and experimental approach in this work. The existence of a turbine obstructs a tidal flow to divert the flow passing through the narrow channel in between the blades and seabed. Flow suppression is the main cause behind inducing tidal turbine scouring, and its accelerated velocity is being termed as tip-bed velocity (Vtb). A theoretical equation is currently proposed to predict the tip-bed velocity based on the axial momentum theory and the conservation of mass. The proposed tip-bed velocity equation is a function of four variables of rotor radius (r), tip-bed clearance (C), efflux velocity (V0) and free flow velocity (V∞), and a constant of mass flow coefficient (Cm) of 0.25. An experimental apparatus was built to conduct the scour experiments. The results provide a better understanding of the scour mechanism of the horizontal axis tidal turbine-induced scour. The experimental results show that the scour depth is inversely proportional to tip-bed clearance. Turbine coefficient (Kt) is proposed based on the relationship between the tip-bed velocity and the experimental tidal turbine scour depth. Inclusion of turbine coefficient (Kt) into the existing pier scour equations can predict the maximum scour depth of a tidal turbine with an error range of 5–24%.

    Documents

    DOI

    Original languageEnglish
    Pages (from-to)1-23
    JournalEnergies
    Journal publication date25 Jun 2019
    Issue number2450
    Volume12
    DOIs
    Publication statusPublished - 25 Jun 2019

      Research areas

    • marine renewable energy; tidal power; tidal turbine-induced scour; turbine wake

    ID: 173963795