Controls-Oriented Model for Secondary Effects of Wake Steering

Abstract

Abstract. This paper presents a model to incorporate the secondary effects of wake steering in large arrays of turbines. Previous models have focused on the aerodynamic interaction of wake steering between two turbines. The model proposed in this paper builds on these models to include yaw-induced wake recovery and secondary steering seen in large arrays of turbines when wake steering is performed. Turbines operating in yaw misaligned conditions generate counter-rotating vortices that entrain momentum and contribute to the deformation and deflection of the wake at downstream turbines. Rows of turbines can compound the effects of wake steering that benefit turbines far downstream. This model quantifies these effects and demonstrates that wake steering has greater potential to increase the performance of a wind farm due to these counter-rotating vortices especially for large rows of turbines. This is validated using numerous large eddy simulations for two-turbine, three-turbine, five-turbine, and wind farm scenarios.

Design and analysis of a wake steering controller with wind direction variability

“…Additionally, more realistic wake models are being developed based on new insights into the physics of wake steering that may impact how susceptible wake steering is to wind direction variability. For example, the curled wake model presented by Martínez-Tossas et al (2019) and the Gauss-curl hybrid wake model developed by King et al (2020), inspired by observations from CFD simulations discussed by Fleming et al (2018), consider how trailing vortices resulting from yaw misalignment interact with the wake to not only deflect it but also change its shape. Fleming et al (2018) discuss how the trailing vortices created by multiple turbines can merge, creating large-scale structures in the flow that could potentially be used to entrain higher energy flow from above the wind farm.…”

Continued Results from a Field Campaign of Wake Steering Applied at a Commercial Wind Farm: Part 2

“…In Bastankhah and Porté-Agel (2019), a detailed wind-tunnel-based study showed that for arrays of turbines performing wake steering, the best strategy is for each successive turbine in a column to have a reduced yaw offset from the one directly upstream. Recently, the Gauss-curl hybrid (GCH) model was introduced in King et al (2019). This model proposes an analytic implementation of the vortices of the curl model of Martínez-Tossas et al (2019) to modify an underlying Gauss model of Bastankhah and Porté-Agel (2014); Niayifar and Porté-Agel (2015); Bastankhah and Porté-Agel (2016).…”

“…This model proposes an analytic implementation of the vortices of the curl model of Martínez-Tossas et al (2019) to modify an underlying Gauss model of Bastankhah and Porté-Agel (2014); Niayifar and Porté-Agel (2015); Bastankhah and Porté-Agel (2016). This latest model will be used in this study and a brief overview of its theory will be included in this paper; see King et al (2019) for a full description.…”

“…for secondary steering (see Fleming et al (2018b)) and yaw-added wake recovery, which models the additional gains in power as an additional increase in flow velocity driven by the counter-rotating vortices. For a detailed description, see King et al (2019).…”

“…However, this is likely related to an issue in modeling near wakes, which both cases represent (3D and 5D spacing) to some extent. In King et al (2019), GCH predicts wrong-way steering better at distances above 5D.…”