The aim of this study is to compare the performance of a linear model to a nonlinear model focusing on flow separation based on a critical slope value. Specifically, the WindPRO WAsP model will be compared with the WindSIM CFD model over a simulated terrain to determine the point the two models differ in relation to the inclination of the terrain. The results of this study will verify if the proposed critical slope value of roughly 17 degrees is truly representative of the limitation of the WAsP model in producing accurate results as compared to a CFD model.  Multiple similar studies have been performed using existing sites with actual met mast data as a comparison to the model outputs. Many of these cases have come up with varying results due primarily to the large number of uncontrolled factors influencing the data. This study will be designed in a fully simulated environment where all variables can be controlled, allowing for the manipulation of a single variable to understand its’ specific influence over the model. The primary variable being tested in this study will be the slope of the terrain with all other factors held constant.   Based on the outcome of 7 alternative runs with ridge heights of 100, 120, 140, 160, 180, 200, and 300 meters and respective maximum slope values of 10.31, 12.32, 14.29, 16.23, 18.14, 20, and 28.63 degrees a defined separation point at a hub height of 94 meters could not be found. Each run demonstrated correlation between wind speeds and terrain slope variations but a considerable difference in estimated wind resources was present between the linear and non-linear CFD models where any slope in terrain is present. This, as expected, increases where terrain inclination increases, but a clearly defined difference between the two models is not evident at the previously established critical slope value of approximately 17 degrees (30%).

This diploma thesis is considering with computational modeling of flow field with separation. In the first part it contains theoretical bases of flow field computational modeling with RANS models equations and wall treatment modeling approaches included. There is also flow separation in asymmetric plane diffuser modeling described in the thesis where the most suitable turbulent model and the proper mesh parameters for the successful flow separation modeling should be chosen. Next the chosen turbulent model and parameters verification via flow separation modeling on the asymmetric 3D diffuser mesh. That analysis should ensure if the chosen turbulent model is applicable also for engineering problems. At the end of the thesis there is evaluation if the setup chosen in the thesis is suitable to apply in any practical aeroacoustics problem modeling.