Treatment of lateral boundary conditions in complex terrain wind simulations

Reliable predictions of atmospheric boundary layer flows over complex terrain is imperative for a variety of applications such as wind energy, aviation, and wildfire control. The large-eddy simulation (LES) technique with provisions for near-surface parameterization is commonly used in complex terrain wind simulations. The accuracy of the LES technique depends strongly on the turbulent inflow generation method used in the simulations. An arbitrarily complex terrain poses unique challenges to develop a reliable yet computationally inexpensive turbulent inflow generation method. Here, we consider the numerical treatment of the entire lateral boundaries for a complex terrain wind simulation with arbitrary inflow direction. We demonstrate inherent flaws in existing methods and provide improvements to the overall lateral boundary conditions as well as the so-called perturbation box method to generate turbulence in the approaching flow. The Askervein Hill field experiment is used to demonstrate the benefits of the proposed improvements.