The characterisation of the hydrodynamic loads on tidal turbines due to turbulence

RENEWABLE & SUSTAINABLE ENERGY REVIEWS

卷:56

Review

Milne, I. A.¹  Day, A. H.²  Sharma, R. N.¹  Flay, R. G. J.¹ 

[1] Univ Auckland, Dept Mech Engn, Auckland Mail Ctr, Private Bag 92019, Auckland 1142, New Zealand

[2] Univ Strathclyde, Dept Naval Architecture & Marine Engn, Henry Dyer Bldg,100 Montrose St, Glasgow G4 0LZ, Lanark, Scotland

关键词: Tidal turbine;    Turbulence;    Unsteady hydrodynamics;    Model-scale testing;   

DOI  :  10.1016/j.rser.2015.11.095

来源: Elsevier

【 摘 要 】

An improved characterisation of the hydrodynamic blade loads due to onset turbulence is essential in order to mitigate premature failures, reduce excessive levels of conservativeness and ultimately ensure the commercial viability of tidal turbines. The literature focussing on the turbulence in fast flowing tidal streams and of the unsteady loads that are subsequently imparted to rotors has previously been very limited. However, increased activity in the tidal energy community has led to new investigations and insights which are reported in this paper. It has been found that through the use of acoustic Doppler-based sensors, the streamwise turbulence intensities generally tend to a value of approximately 6-8% at the mid-depth of proposed tidal energy sites. Evidence that the anisotropic structure and scales of the turbulence are more consistent with open channel-based models than atmospheric-based correlations has also been found. Rapid distortion theory has been applied to estimate that the standard deviation of the streamwise turbulent velocity fluctuations in the onset free-stream flow may be amplified significantly by 15% due to the presence of a turbine. The turbulent fluctuations have also been predicted to remain well correlated over the outer span of the blades at the rotational frequency of the rotor. Recent model-scale experiments have enabled the unsteady hydrodynamic loading to be isolated from the steady-flow loading. For cases where the boundary layer remains primarily attached across the blades, this has enabled linear transfer functions to be developed and applied to model the response to a multi-frequency forcing. It has also been found that phenomena consistent with delayed separation and dynamic stall can result in a blade root bending moment that exceeds the steady value by 25%, and this needs to be taken into account in design to reduce the probability of failure. (C) 2015 The Authors. Published by Elsevier Ltd.

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