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

¹ Fraunhofer IWES, Ammerländer Heerstr. 136, 26129 Oldenburg, Germany
² Carl von Ossietzky University, 26111 Oldenburg, Germany
³ Fachhochschule Kiel, Sokratesplatz 1, 24149 Kiel, Germany

^a e-mail: carlos.peralta@iwes.fraunhofer.de
^b e-mail: habtom.nugusse@uni-oldenburg.de
^c e-mail: prakashqd@gmail.com
^d e-mail: jonas.schmidt@iwes.fraunhofer.de
^e e-mail: bernhard.stoevesandt@iwes.fraunhofer.de

Abstract

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.