Hi witor,
answers to your questions.
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unless you have any validation data and already did very much work into mesh analysis I wouldn’t suggest you change the numeric values and with that values for k -omega.
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I would usually suggest using wall function since full resolution of walls usually takes too many cells. With wall function, you can save a good amount of cells and be still very accurate.
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In terms of drag SimScale does take both pressure and viscous effects in account when calculating the reactive force. You can find out more about force coefficients here:
How To Analyze the Pitch, Lift, and Drag Coefficients | SimScale -
If I’m right you are of by 5% which is very good for a sphere since spheres are actually quite tricky to solve since the drag of a sphere is very dependent on the Reynolds number which can bring various transient effect with them.
I hope I could help you with your question.
Best regards
Sebastian