Modeling dynamic wind direction changes in large eddy simulations of wind farms

The wind direction in atmospheric boundary layers changes continuously due to meso-scale weather phenomena. Developing accurate simulations of these changes is essential for understanding their effect on the performance of large wind farms. Our study introduces a new technique to model dynamic wind direction changes obtained from meso-scale simulations or field measurements in micro-scale large eddy simulations. We propose a method in which the simulation domain is treated as a non-inertial rotating reference frame. The primary benefit of our approach is that it is straightforward to implement and reproduces desired wind direction changes excellently. We verified our approach in neutral atmospheric boundary layers and show that the observed boundary-layer characteristics for dynamic wind directions agree very well with those observed for constant mean wind directions when the wind direction is changed slowly such that the flow is quasi-stationary. Further, we show that atmospheric measurements of the wind direction can be reproduced by our method. To underline the importance of the method, we conclude with a representative scenario, which shows that dynamic wind direction changes can affect the performance of large wind farms.