May i also know...as i have just copied youtube video...as they were giving velocity to fluid flow not to vessel.....so why not i let fluid velocity at inlet remain zero(0) and should provide velocity to my ship in forward direction only........as it is calm water test, where water remain calm, i believe this should be the right way to simulate ship in calm water with letting it free in pitch and heave...please can you tell, my thinking is correct?

In Star CCM +...........VOF waves are chosen even if there are no waves present, but the calm water is actually
specified as a flat wave.
Do we also have to choose "flat wave" option as we are simulating calm water test..and from where to choose "flat wave" option in fluent?