Validation of the simpleFoam (RANS) solver for the atmospheric boundary layer in complex terrain

We validate the simpleFoam (RANS) solver in OpenFOAM (version 2.1.1) for simulating neutral atmospheric boundary layer flows in complex terrain. Initial and boundary conditions are given using Richards and Hoxey proposal (1). In order to obtain stable simulation of the ABL, modified wall functions are used to set the near-wall boundary conditions, following Blocken et al remedial measures (2). A structured grid is generated with the new library terrainBlockMesher (3, 4), based on OpenFOAM's blockMesh native mesher. The new tool is capable of adding orographic features and the forest canopy. Additionally, the mesh can be refined in regions with complex orography. We study both the classical benchmark case of Askervein hill (5) and the more recent Bolund island data set (6). Our purpose is two-folded: to validate the performance of OpenFOAM steady state solvers, and the suitability of the new meshing tool to generate high quality structured meshes, which will be used in the future for performing more computationally intensive LES simulations in complex terrain. Site selection for wind energy projects is a critical step of the decision making process for possible investment in wind energy. On-site measurement campaigns over areas of several kilometers square for wind farm siting can be very costly, and can only provide a local assessment of wind conditions. To overcome this hurdle it is currently very common to recur to computational fluid dynamics (CFD) simulations that can extend meteorological mast point source measurement data over an area of several kilometers. Nowadays computational fluid dynamics (CFD) modeling for the atmospheric boundary layer (ABL) in complex terrain is becoming more ubiquitous, although it is quite time demanding to perform numerical solutions of the governing fluid equations without making simplifications to the flow dynamics. The most common approach used for ABL flows are the Reynold Averaged Navier

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