I have been trying to simulate the turning circle trajectory of ship using star CCM+. I was rtying to rotate rudder once the velocity becomes steady. As in intial stage am trying with propulsive force method. ie, giving direct force at the CG of the vessel. But the problem is once i give all 6DOF under DFBI-Free motion module, vessel strats to turn without any rudder action. Why this is happening...? Any idea
The rotation is produced by a net moment at the CG.
To see what is the origin of the net moment you could make use of the DFBI displayers to show the
forces, and in this case, the moments acting on your ship.
Please note that STAR-CCM+ has specific motions for ship manoeuvrability.
Concerning your problem, maybe our self-propulsion tutorial could be a good start. You could add your rudder with a joint using our multibody motion, and then change the angle of your rudder, as in real life.
If nothing of the above helps, then a .sim file would help for more detailed diagnosis.