Influence of a velocity profile &amp; support structure on tidal stream turbine performance

Mason-Jones, Allan; O'Doherty, Daphne Maria; Morris, Ceri; O'Doherty, Timothy

doi:10.1016/j.renene.2012.10.022

“…Their time-averaged LES results of the power coefficient exhibited regular pronounced fluctuations as a function of blade angle with the rotors upstream; in the RANS simulations, these were absent. The RANS models of Mason-Jones et al [67], however, did predict increased fluctuations in torque with blade angle when the stanchion supporting the turbine was included. The lesson here is that care must be used when deploying RANS turbulence schemes to capture transient behaviour in diagnostics.…”

Section: Discussionmentioning

confidence: 92%

Effects of Support Structures in an LES Actuator Line Model of a Tidal Turbine with Contra-Rotating Rotors

Creech

¹

,

Borthwick

²

,

Ingram

³

2017

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Abstract:Computational fluid dynamics is used to study the impact of the support structure of a tidal turbine on performance and the downstream wake characteristics. A high-fidelity computational model of a dual rotor, contra-rotating tidal turbine in a large channel domain is presented, with turbulence modelled using large eddy simulation. Actuator lines represent the turbine blades, permitting the analysis of transient flow features and turbine diagnostics. The following four cases are considered: the flow in an unexploited, empty channel; flow in a channel containing the rotors; flow in a channel containing the support structure; and flow in a channel with both rotors and support structure. The results indicate that the support structure contributes significantly to the behaviour of the turbine and to turbulence levels downstream, even when the rotors are upstream. This implies that inclusion of the turbine structure, or some parametrisation thereof, is a prerequisite for the realistic prediction of turbine performance and reliability, particularly for array layouts where wake effects become significant.

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“…Their time-averaged LES results of the power coefficient exhibited regular pronounced fluctuations as a function of blade angle with the rotors upstream; in the RANS simulations these were absent. The RANS models of Mason-Jones et al [64] however, did predict increased fluctuations in torque with blade angle when the stanchion supporting the turbine was included. The lesson here is that care must be used when deploying RANS turbulence schemes to capture transient behaviour in diagnostics.…”

Section: Discussionmentioning

confidence: 95%

Effects of Support Structures in an LES Actuator Line Model of a Tidal Turbine with Contra-rotating Rotors

Creech¹,

Borthwick²,

Ingram³

2017

Preprint

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Abstract:Computational fluid dynamics is used to study the impact of the support structure of a tidal turbine on performance and the downstream wake characteristics. A high-fidelity computational model of a dual rotor, contra-rotating tidal turbine in a large channel domain is presented, with turbulence modelled using large eddy simulation. Actuator lines represent the turbine blades, permitting the analysis of transient flow features and turbine diagnostics. The following four cases are considered: the flow in an unexploited, empty channel; flow in a channel containing the rotors; flow in a channel containing the support structure; and flow in a channel with both rotors and support structure. The results indicate that the support structure contributes significantly to the behaviour of the turbine and to turbulence levels downstream, even when the rotors are upstream. This implies that inclusion of the turbine structure, or some parametrisation thereof, is a prerequisite for the realistic prediction of turbine performance and reliability, particularly for array layouts where wake effects become significant.

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“…Data for both horizontal-axis [1,33] and vertical-axis turbines [34] show there is a relationship between C P and C T . Although the relationship is non-linear, these data confirm that the thrust coefficient is greater than the power coefficient.…”

Section: Numerical Approach To Representation Of Turbinesmentioning

confidence: 96%

“…Mechanical losses will act to reduce the theoretical C P . Experimental tests of scaled horizontal-axis turbines by [1] recorded a maximum C P of 0.46 and a corresponding C T of 0.8 (for a blade pitch angle of 20˝) while the high resolution near-field modelling study of [33] recorded a maximum C P of 0.4 and a corresponding C T of 0.88 (for a blade pitch angle of 6˝). These values of C P and C T were recorded for particular flow speeds and C P and C T will vary with flow speed across the turbine.…”

Section: Numerical Approach To Representation Of Turbinesmentioning

confidence: 99%

Towards a Low-Cost Modelling System for Optimising the Layout of Tidal Turbine Arrays

Olbert

¹

,

Hartnett

²

2015

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Abstract:In the long-term, tidal turbines will most likely be deployed in farms/arrays where energy extraction by one turbine may significantly affect the energy available to another turbine. Given the prohibitive cost of experimental and/or field investigations of such turbine interactions, numerical models can play a significant role in determining the optimum layout of tidal turbine arrays with respect to energy capture. In the present research, a low-cost modelling solution for optimising turbine array layouts is presented and assessed. Nesting is used in a far-field model to telescope spatial resolution down to the scale of the turbines within the turbine array, allowing simulation of the interactions between adjacent turbines as well as the hydrodynamic impacts of individual turbines. The turbines are incorporated as momentum sinks. The results show that the model can compute turbine wakes with similar far-field spatial extents and velocity deficits to those measured in published experimental studies. The results show that optimum spacings for multi-row arrays with regard to power yield are 3-4 rotor diameters (RD) across-stream and 1-4 RD along-stream, and that turbines in downstream rows should be staggered to avoid wake effects of upstream turbines and to make use of the accelerated flows induced by adjacent upstream turbines.

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Influence of a velocity profile & support structure on tidal stream turbine performance

Cited by 67 publications

References 4 publications

Effects of Support Structures in an LES Actuator Line Model of a Tidal Turbine with Contra-Rotating Rotors

Effects of Support Structures in an LES Actuator Line Model of a Tidal Turbine with Contra-Rotating Rotors

Effects of Support Structures in an LES Actuator Line Model of a Tidal Turbine with Contra-rotating Rotors

Towards a Low-Cost Modelling System for Optimising the Layout of Tidal Turbine Arrays

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