Shear layer approximation of Navier-Stokes steady equations for non-axisymmetric wind turbine wakes: Description, verification and first application

Abstract

The number of turbines installed in offshore wind farms has strongly increased in the last years and at the same time the need for more precise estimation of the wind farm efficiency. For this reason, the wind energy community could benefit from more accurate models for multiple wakes. Existing engineering models can only simulate single wakes, which are superimposed if they are interacting in a wind farm. This method is a practical solution, but it is not fully supported by a physical background. The limitation to single wakes is given by the assumption that the wake is axisymmetric. As alternative, we propose a new shear model which is based on the existing engineering wake models, but is extended to simulate also non- axisymmetric wakes. In this paper, we present the theoretical background of the model and two application cases. First, we proved that for axisymmetric wakes the new model is equivalent to a commonly used engineering model. Then, we evaluated the improvements of the new model for the simulation of a non-axisymmetric wake using a large eddy simulation as reference. The results encourage the further development of the model, and promise a successful application for the simulation of multiple wakes.