UKERC EDC: Publications

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Abstract:

The Performance Assessment of Wave and Tidal Array Systems (PerAWaT) project, launched in October 2009 with £8m of ETI investment. The project delivered validated, commercial software tools capable of significantly reducing the levels of uncertainty associated with predicting the energy yield of major wave and tidal stream energy arrays. It also produced information that will help reduce commercial risk of future large scale wave and tidal array developments.

This report contains results and analysis of 3D RANS simulated flows through a generic full scale tidal turbine operating in various flow conditions. Conditions simulated include varying levels of shear, vertical position through the water column, turbine spacing and yaw angle. Additionally simulations of a towerless rotor are presented, including a comparison to the results of the University of Edinburgh model ofthe same towerless rotor. Results presented include thrust and power metrics as well as wake profiles. Results are analysed and contrasted with respect to perturbations in each flow condition leading to observations on their influence.

In particular shear is observed to increase the power delivered by the turbine (with mass flux through the channel held constant), as is increasing the elevation of the turbine through the shear profile. Additionally shear is observed to increase the rate of wake recovery. Reducing the lateral spacing, and therefore increasing the area blockage ratio, increases the thrust and power delivered by the turbine, consistent with existing theory. Removing the tower from the simulations increases the thrust and power experienced by the turbine, as well as removing the torque ripple. Lower power is extracted by the turbine when operating in yawed flows,and a lower thrust coefficient is observed. However, the blade loading is distinctly different from the unyawed cases, as shown in plots of azimuthally-distributed rotor torque.

Comparison to the University of Edinburgh simulation results is done on a consistent area blockage basis.

The turbine wake is parameterised by considering a force balance for a turbine operating in a confined flow, and converting the resulting ‘top-hat’ wake velocity profile into an Gaussian distribution with equivalent momentum and standard deviation. This model is valid at the end of the near-wake. The near-wake ends at a downstream location where the pressure has equalised in the cross-stream directionand the velocity profile exhibits a self-similar form. For the current set of simulations this point has been identified at a distance of five diameters downstream of the rotor plane.

Relationships between operating conditions and wake model parameters are determined.

All of the results presented here are based on unsteady blade-resolved simulations, where the simulated flow field has been averaged over one full rotor revolution.

Publication Year:

2012

Publisher:

ETI

DOI:

https://doi.org/10.5286/ukerc.edc.000413

Author(s):

Fleming, C.F., McIntosh, S.C. and Willden, R.H.J.

Energy Category

Class Name:

Subclass Name:

Category Name:

Renewable Energy Sources

Ocean Energy

Language:

English

File Type:

application/pdf

File Size:

4302397 B

Rights:

Energy Technologies Institute Open Licence for Materials

Rights Overview:

The Energy Technologies Institute is making this document available to use under the Energy Technologies Institute Open Licence for Materials. Please refer to the Energy Technologies Institute website for the terms and conditions of this licence. The Information is licensed "as is" and the Energy Technologies Institute excludes all representations, warranties, obligations and liabilities in relation to the Information to the maximum extent permitted by law. The Energy Technologies Institute is not liable for any errors or omissions in the Information and shall not be liable for any loss, injury or damage of any kind caused by its use. This exclusion of liability includes, but is not limited to, any direct, indirect, special, incidental, consequential, punitive, or exemplary damages in each case such as loss of revenue, data, anticipated profits, and lost business. The Energy Technologies Institute does not guarantee the continued supply of the Information. Notwithstanding any statement to the contrary contained on the face of this document, the Energy Technologies Institute confirms that it has the right to publish this document.

Further information:

N/A

Region:

United Kingdom

Publication Type:

Technical Report

Subject:

Technology

Theme(s):

Marine

Related Dataset(s):

No related datasets