Drillships have specific features which make ship resistance and propulsion characteristics difficult to predict with simple empirical methods. In this paper, RANSE CFD was used to optimize the hull and appendages of a drillship for speed or fuel consumption. An innovative thruster arrangement was initially designed for dynamic positioning and its performance in transit was verified with the use of CFD. Furthermore a special hydrodynamically shaped moonpool has been developed to eliminate moonpool sloshing during transit, further reducing resistance and increasing safety on board.
CFD was also used to determine the propulsion efficiencies of the vessel. An innovative way to use an actuator disc approach was used to calculate effective wake factors.
The various CFD calculations and the resulting design modifications are verified and confirmed with calm water resistance and self-propulsion tests.
The bow shape modifications reduce the bare hull resistance by 12% and the headbox modifications reduce the added headbox resistance by 26% of the bare hull resistance. The Callirrhoe moonpool design reduces the added moonpool resistance by 37% compared to a conventional moonpool while at the same time eliminates sloshing in transit. The propulsion efficiency is above 60% when the aft thrusters are used, which is deemed high for such a vessel.