Toward validation of an overset CFD flow solver for wind energy applications.

The analysis and design of the next generation of wind farms relies on the accurate numerical prediction of the turbulent airflow around multiple wind turbines. This computational aerodynamic problem is characterized by an atmospheric turbulent inflow, multiple bodies in relative motion, i.e. rotors and towers, and complex wake interactions. Furthermore, the size of the computational domain requires the numerical resolution of length scales that vary from several kilometers to the viscous length scales of the boundary layer of the blades. Overset-grids Computational Fluid Dynamics methods (CFD) offer an elegant and efficient solution for the simulation of blade-resolved wind farm aerodynamic problems: multiple body-conforming meshes can be embedded in several wake-capturing grids of different resolution. In this work, we present the initial validation of Nalu-Wind, an overset unstructured CFD flow solver for wind energy applications. The accuracy of the newly implemented overset methodology is investigated by simulating the complex unsteady airflow around a modern wind turbine airfoil and the turbulent flow around a NACA 0015 wing.