Answer:
The settings for the wind simulation can also be adjusted in the main program in RFEM 6 and RSTAB 9.
In RFEM 6, you can find the settings for model simplification in the submenu of the mesh settings.
In RSTAB 9, you can find the settings for the model simplification in the menu item Wind Simulation Model Simplification.
Further settings regarding the flow parameters, options, and calculation parameters can be adjusted directly in the wind simulation analysis settings.
