Performance of an ideal turbine in an inviscid shear flow

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dc.contributor.authorDraper, S.
dc.contributor.authorNishino, Takafumi
dc.contributor.authorAdcock, T. A. A.
dc.contributor.authorTaylor, P. H.
dc.date.accessioned2016-06-27T09:30:09Z
dc.date.available2016-06-27T09:30:09Z
dc.date.issued2016-04-28
dc.description.abstractAlthough wind and tidal turbines operate in turbulent shear flow, most theoretical results concerning turbine performance, such as the well-known Betz limit, assume the upstream velocity profile is uniform. To improve on these existing results we extend the classical actuator disc model in this paper to investigate the performance of an ideal turbine in steady, inviscid shear flow. The model is developed on the assumption that there is negligible lateral interaction in the flow passing through the disc and that the actuator applies a uniform resistance across its area. With these assumptions, solution of the model leads to two key results. First, for laterally unbounded shear flow, it is shown that the normalised power extracted is the same as that for an ideal turbine in uniform flow, if the average of the cube of the upstream velocity of the fluid passing through the turbine is used in the normalisation. Second, for a laterally bounded shear flow, it is shown that the same normalisation can be applied, but allowance must also be made for the fact that non-uniform flow bypassing the turbine alters the background pressure gradient and, in turn, the turbines ‘effective blockage’ (so that it may be greater or less than the geometric blockage, defined as the ratio of turbine disc area to cross-sectional area of the flow). Predictions based on the extended model agree well with numerical simulations approximating the incompressible Euler equations. The model may be used to improve interpretation of model-scale results for wind and tidal turbines in tunnels/flumes, to investigate the variation in force across a turbine and to update existing theoretical models of arrays of tidal turbines.en_UK
dc.identifier.citationS. Draper, T. Nishino, T. A. A. Adcock and P. H. Taylor. Performance of an ideal turbine in an inviscid shear flow. Journal of Fluid Mechanics, Volume 796, June 2016, pp 86-112en_UK
dc.identifier.issn0022-1120
dc.identifier.urihttp://dx.doi.org/10.1017/jfm.2016.247
dc.identifier.urihttp://dspace.lib.cranfield.ac.uk/handle/1826/10028
dc.language.isoenen_UK
dc.publisherJournal of Fluid Mechanicsen_UK
dc.rightsAttribution-NonCommercial 4.0 International
dc.rights.urihttp://creativecommons.org/licenses/by-nc/4.0/
dc.subjectcoastal engineeringen_UK
dc.subjectgeophysical and geological flowsen_UK
dc.subjectshallow water flowsen_UK
dc.titlePerformance of an ideal turbine in an inviscid shear flowen_UK
dc.typeArticleen_UK

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