An actuator line method with novel blade flow field coupling based on potential flow equivalence

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Abstract

A Reynolds-averaged Navier–Stokes-embedded actuator line model for wind and tidal turbine simulation has been implemented and validated using the National Renewable Energy Laboratory Phase VI wind tunnel experimental results. Actuator line models, first introduced by Sørensen and Shen, represent the blades virtually, enabling time-resolved rotor simulations without requiring blade boundary layer discretization. This results in a lower computational cost than blade-resolved simulations while preserving the predominant features of the rotor flow. The present method introduces a novel technique, based on potential flow equivalence, to determine the local flow velocity at the blade, and a method of projecting the resulting momentum sources to the flow field. These methods circumvent the requirement for smearing techniques used in other actuator line models. In addition, the model is adapted for use with an unstructured mesh, thereby enabling turbine components such as the tower and nacelle to be explicitly included in the domain. The model is validated through comparison of computed integrated loads and local force coefficients with the National Renewable Energy Laboratory Phase VI experimental results. Results for local force coefficients indicate general agreement with experiment, although discrepancies associated with three-dimensional flow effects are observed at the tips. Copyright © 2014 John Wiley & Sons, Ltd.

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