Recently, I simulated the wake of 2D rotating tyre using overset mesh. I had to leave a 1 cm gap between the tyre and ground. I wonder if I can conduct CFD of 3D tyre in contact with the ground?
You are not mentioning the CFD code which you are using. I would be a bit astonished, if the 1cm gap would be necessary with overset mesh in ANSYS Fluent as well. But I had not yet a chance to try this by myself.