Large-Eddy and Reynolds-Averaged-Navier Stokes simulations of the Kassel forested hill - Rödeser Berg (Deliverable D2.13)

This report summarizes RANS and LES simulation results from model runs of the Rödeser Berg site near Kassel and is separated into two parts. The first part focuses on LES simulation results from a series of sensitivity studies carried out at the Rödeser Berg site to investigate the model’s sensitivity towards forest representations and grid resolution. The results indicate that a representation of the forest in terms of roughness only is not capable in correctly resolving the wind conditions on top of a forested hill, while a forest parametrization that accounts for the drag in the lowest grid cells improves the results significantly. The second part of the report summarizes the (anonymous) results of the first round of benchmarks carried out at the Rödeser Berg site where several RANS and LES modelers handed in simulated wind profiles at several locations during a southwesterly flow. These model results are compared to wind profile measurements at different positions across the Rödeser Berg. The results indicate that neutrally stratified situations can be modeled well by most models but, especially in forested areas, the model results strongly depend on the forest model chosen. In stably stratified situations the model results strongly differ, especially in areas downstream of topography features, i.e. the wakes of hills. Further research is needed in these areas. The Rödeser Berg experimental data offer a great opportunity for future further validation of models and verification of new models and parameterizations against measurement data