Dear all, it is not clear to me what is meant in Fluent by "radial" and "tangential" velocity .Specifically, in my problem of flow around a cyilinder, radial velocity on cylinder surface ("shadow") is different from zero and of the same order of tangential velocity. Can anybody also explain me better what is a "shadow" and why do I have these high velocities there? Thanks for your attention

(1). If you are using someone's code, you should contact the vendor of the code. (2). It is their responsibility to tell you how the code works, especially how they handle the surface boundary conditions.

radial/tangential is defined by the "coordinate-system" you set in define/boundary-conditions/fluid. You find there a "rotation-axis".

shadow appears, if you define a wall with thickness=0. Then you need a wall on the one side and one wall to the other side (and this one is the shadow-wall).

The velocities are extrapolated to the walls. Use x/y/z-velocity for velocities on the walls (or functions from those). They give exact "0".walls.