Three-dimensionality of the wake recovery behind a vertical axis turbine

RENEWABLE ENERGY

卷:133

Article

Ouro, Pablo¹  Runge, Stefan¹  Luo, Qianyu¹  Stoesser, Thorsten¹ 

[1] Cardiff Univ, Sch Engn, Hydroenvironm Res Ctr, Cardiff CF24 3AA, S Glam, Wales

关键词: Vertical axis turbine;    Wake recovery;    Array;    Acoustic Doppler velocimeter;    Turbulence;    Renewable energy;   

DOI  :  10.1016/j.renene.2018.10.111

来源: Elsevier

【 摘 要 】

The wake recovery downstream of a vertical axis turbine operating in a turbulent channel flow is investigated via detailed velocity measurements using an Acoustic Doppler Velocimeter. Three distinct wake regions are identified: (i) a near-wake region which extends until two rotor diameters (2D) downstream and characterised by a low-momentum area isolated from the ambient flow and the presence of energetic dynamic stall vortices; (ii) a transition region (2D-5D), characterised by a fast momentum recovery, high levels of turbulence and vertical expansion of the wake; and (iii) a far-wake region beyond 5D where the velocity recovers to approximately 95% of the free-stream velocity. Albeit the wake deficit recovery is mostly accomplished at 5D behind the turbine, rotor-induced effects are still present beyond 10D as indicated by high-order flow statistics, such as high velocity fluctuations and flow skewness. The analysis of the streamwise momentum budget reveals that advection is the main mechanism for momentum replenishment through most of the wake and turbulent transport terms play only a minor role. This study evidences the anisotropic nature of the turbulence and asymmetry of the flow in horizontal, vertical and cross-sectional planes downstream of the vertical axis turbine. (C) 2018 Elsevier Ltd. All rights reserved.

【 授权许可】

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