{"id":863,"date":"2011-06-17T10:33:04","date_gmt":"2011-06-17T10:33:04","guid":{"rendered":"http:\/\/dev.blogs.soton.ac.uk\/serg\/?p=863"},"modified":"2013-12-18T10:45:50","modified_gmt":"2013-12-18T10:45:50","slug":"actuator-disc-rans-modelling-for-tidal-turbines","status":"publish","type":"post","link":"https:\/\/blog.soton.ac.uk\/serg\/actuator-disc-rans-modelling-for-tidal-turbines\/","title":{"rendered":"Actuator Disc-Rans modelling for tidal turbines"},"content":{"rendered":"

Title: The accuracy of the actuator Disc-Rans approach for modelling\u00a0performance\u00a0and wake characteristics of a\u00a0horizontal\u00a0axis tidal stream turbine.<\/h3>\n

Researcher: Matt Harrison<\/h3>\n

Supervisors: William Batten & AbuBakr Bahaj<\/h3>\n

 <\/p>\n

Abstract<\/h2>\n

Tidal stream energy has the potential to supply power with low carbon dioxide emissions, but the\u00a0technology is still being developed. Horizontal axis tidal stream turbines have seen the greatest\u00a0development, and to generate energy at a commercial scale they will be installed in multi-device\u00a0arrays. In the array, performance of downstream devices will be affected by the wake of those\u00a0upstream. The actuator disc-RANS model can be used to optimise array configuration.<\/p>\n

A review of previous studies which used actuator disc-RANS showed that the model has\u00a0been implemented with a wide range of parameters (boundary conditions, turbulence model,\u00a0turbine model and dimensions), and predictions of velocity magnitudes in the wake of a turbine\u00a0varied between similar published studies. The accuracy of the model for tidal turbines has not\u00a0been demonstrated, and appropriate parameters for applying the model are not apparent from\u00a0previous work. Without validation the model may not be applied to arrays with confidence. The\u00a0purpose of this thesis is to identify appropriate parameters,\u00a0and to demonstrate their accuracy\u00a0through verification and validation studies.<\/p>\n

The first aspect of the work is to identify parameters which achieve accurate predictions\u00a0using the uniform turbine model. If the k \u2212 \u03b5<\/em>\u00a0turbulence model, turbulence sources at the disc,\u00a0and a free-slip wall to model the free surface are used, the model produces accurate results.\u00a0Comparison to centreline velocities measured experimentally in the wake of a porous disc gives\u00a0a coefficient of determination of 0.61-0.97 depending on the turbine thrust coefficient, with a\u00a0maximum discretization error of 1.5%. Comparison to centreline velocities measured in the wake\u00a0of a scaled tidal stream turbine gives a coefficient of determination of 0.92 at a thrust coefficient\u00a0of 1, and a maximum discretization error of 9%.\u00a0When the blade-element actuator disc turbine model is used comparison to measured centreline\u00a0wake velocities gives a coefficient of determination of 0.94 at a thrust coefficient of 1, and\u00a0a maximum discretization error of 9%. Comparison of turbine power coefficient shows that the\u00a0model under predicts experimental data by between 2% at low tip speed ratio, and 9% at high\u00a0tip speed ratio.<\/p>\n

The second aspect examines the capability of the turbine models to predict the power output\u00a0from an array. A comparison between the uniform, and blade element actuator disc, finds that\u00a0the blade element model predicts 13% higher power output due to compounded differences\u00a0between the models over the array. Modelling the support structure increases predicted power\u00a0output by 0.2%. Results also show that if ambient turbulence intensity is increased from 15%\u00a0to 40%, overall power output from the array increases by 14%.<\/p>\n

The results provide array modellers with appropriate parameters to achieve accurate predictions\u00a0using actuator disc-RANS. They demonstrate that the model may be used with confidence\u00a0provided these parameters are used, and discretization error, Froude number and blockage ratio\u00a0are similar to the cases tested. The results also demonstrate the difference between turbine\u00a0models when estimating the power from an array, and a requirement to accurately characterise\u00a0turbulence intensity at a tidal site and represent this data in the model.<\/p>\n

Publications<\/h2>\n

M.E. Harrison, W.M.J. Batten, L.S. Blunden, L.E. Myers, A.S. Bahaj\u00a0(2008)\u00a0Comparisons of a Large Tidal Turbine Array Using the Boundary Layer and Field Wake Interaction Models,\u00a02nd International Conference on Ocean Energy (ICOE)(October),\u00a0p.<\/p>\n

M.E. Harrison, W.M.J. Batten, L.E. Myers, A.S. Bahaj\u00a0(2009)\u00a0A comparison between CFD simulations and experiments for predicting the far wake of horizontal axis tidal turbines,\u00a08th European Wave and Tidal Energy Conference,\u00a0p.<\/p>\n

L.S. Blunden, W.M.J. Batten, M.E. Harrison, A.S. Bahaj\u00a0(2009)\u00a0Comparison of boundary-layer and field models for simulation of flow through multiple-row tidal fences,\u00a08th European Wave and Tidal Energy Conference<\/p>\n

M.E. Harrison, W.M.J. Batten, A.S. Bahaj\u00a0(2010)\u00a0A blade element actuator disc approach applied to tidal stream turbines,\u00a0OCEANS 2010 MTS\/IEEE SEATTLE,\u00a0p. 1-8,\u00a0Seattle: IEEE,\u00a0url<\/a><\/p>\n

M.E. Harrison, W.M.J. Batten, L.E. Myers, A.S. Bahaj\u00a0(2010)\u00a0Comparison between CFD simulations and experiments for predicting the far wake of horizontal axis tidal turbines,\u00a0IET Renewable Power Generation4(6),\u00a0p. 613,\u00a0url<\/a><\/p>\n

T. Blackmore, W.M.J. Batten, M.E. Harrison, A.S. Bahaj\u00a0(2011)\u00a0The Sensitivity of Actuator-Disc RANS Simulations to Turbulence Length Scale Assumptions,\u00a09th European Wave and Tidal Energy Conference<\/p>\n

W.M.J. Batten, M.E. Harrison, A.S. Bahaj\u00a0(2013)\u00a0Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines.,\u00a0Philosophical transactions. Series A, Mathematical, physical, and engineering sciences\u00a0371(1985),\u00a0p. 20120293,\u00a0pubmed<\/a><\/p>\n

Sample Predictions<\/h2>\n
\"\"<\/a>

Typical domain and mesh set-ups used for validation<\/p><\/div>\n

\"\"<\/a>

Validation of power coefficent<\/p><\/div>\n

\"\"<\/a>

Comparison of modelling methods in predicting the wake<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

Title: The accuracy of the actuator Disc-Rans approach for modelling\u00a0performance\u00a0and wake characteristics of a\u00a0horizontal\u00a0axis tidal stream turbine. Researcher: Matt Harrison Supervisors: William Batten & AbuBakr Bahaj   Abstract Tidal stream energy has the potential to supply power with low carbon dioxide emissions, but the\u00a0technology is still being developed. Horizontal axis tidal stream turbines have seen […]<\/p>\n","protected":false},"author":90699,"featured_media":880,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[441138,417955],"tags":[417890,552649,786073],"class_list":["post-863","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-phd-projects","category-tidal-energy","tag-cfd","tag-marine-energy","tag-tidal-energy"],"_links":{"self":[{"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/posts\/863","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/users\/90699"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/comments?post=863"}],"version-history":[{"count":4,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/posts\/863\/revisions"}],"predecessor-version":[{"id":2341,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/posts\/863\/revisions\/2341"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/media\/880"}],"wp:attachment":[{"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/media?parent=863"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/categories?post=863"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.soton.ac.uk\/serg\/wp-json\/wp\/v2\/tags?post=863"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}