Thank you cfdguru for your quick reply.
1)When I chose "direct" for the turbulence input, I didn't see any place pops up asking for the variables (eg. turbulent kinetic energy, eddy frequency), only eddy viscosity is available. Is the setting somewhere else in the GUI? Or setting eddy viscosity is enough?
2) If to choose "direct", how can I find out what turbulence intensity it is using?
3) My case is an external flow over a square obstacle. Shall I use the dimension of the square side for turbulence length scale?
Thank you very much.