Turbulence and wake effects in tidal stream turbine arrays

Nuernberg, Martin and Tao, Longbin (2018) Turbulence and wake effects in tidal stream turbine arrays. In: 37th International Conference on Ocean, Offshore & Arctic Engineering, 2018-06-17 - 2018-06-22.

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    Abstract

    Electricity generation from tidal current can provide a reliable and predictable alternative addition to a reduced carbon energy sector in the future. With increasing commercial development and deployment of the first multi-turbine array, significant cost reduction can be achieved by moving beyond demonstrator projects to large scale tidal turbine arrays. For the operational efficiency and safety, the interactions between multiple turbines installed in close proximity can affect the total electricity generation and thus require knowledge of the resulting flow field within and downstream of the array. This paper present results of an experimental and numerical study investigating the flow field characteristics in terms of velocity deficit and turbulence intensity in a staggered section of a tidal turbine array. Multiple configuration with varying longitudinal and transverse spacing between devices in a three-turbine array are tested. Comparison between numerical and experimental flow characteristics shows that open source numerical models with dynamic mesh features achieve good agreement and can be used for the investigation of array wake effects. The standard k – ω SST shows good agreement with experiments at reduced computational efficiency compared to higher order turbulence models (RSM). Further the importance of mixing with ambient flow is highlighted by identifying areas of significantly reduced velocity recovery within closely spaced tidal turbine arrays where ambient flow does not penetrate between adjacent wakes