Hi there, thank you for reaching out to us!
This is a common question of many users, and my first comment is to always keep in mind that 3D and 2D are expected to have different results.
In order to get as reliable results as possible with your 3D model, make sure to create a good mesh.
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Take into consideration the y+:How to Control and Analyze Y+ in Meshing Simulation | SimScale
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Make sure you have a good mesh quality: How to Control and Analyze Y+ in Meshing Simulation | SimScale
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You can use a similar tutorial as reference: Incompressible Turbulent Flow Around a Spoiler | SimScale
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Use the correct values for the reference length and area: How To Analyze the Pitch, Lift, and Drag Coefficients | SimScale
For example, I see you are using a reference area of 1 m² in your Results Control set up, which does not seem to be the correct value.
Best regards,
Fillia