Ship resistance value not matching with experiments..
 

Hi everyone,
I am trying to estimate the resistance of a ship in Star CCM+ 8.06 using DFBI module.I am getting 20% error when compared to experiments. I have checked the sensitivity of my results wrt to mesh,time- step and domain.
Boundary and initial conditions as per the tutorial "KCS resistance prediction".

Is there anything else I could try..?
Anybody conducted experiments in towing tank and compared with CFD..?
What are other possible sources of error..?

I don't think my question is a new one. Any other details to be provided,folks?
:o