CFD Simulation of the Moonpool on the Total Resistance of a Drillship at Low Forward Speed

A moonpool is meant to access the underwater part of hull from onboard ship. Moonpools are openings right through the hull from deck to bottom, allowing equipments, ROVs, etc. to be put into the water at a location on the vessel under permissible ship motion condition. Open moonpools in a drillship are causing additional resistance when the ship is in forward speed. It was shown that the water inside the moonpool started to oscillate at forward speed. The drillship is mainly subjected to two types of motions of water mass inside the column namely, piston mode and sloshing mode. The later mode will be dominant in longer moonpools and piston mode in shorter. The amplitude of water particles inside the moonpool is correlated with the forward speed such that increased forward speed leads to increased amplitudes. The main objective of this study is to find the total resistance and the free surface flow caused by the moonpool when the drillship is at low forward speed condition. Drillship with and without moonpool are considered for the study. Proven packages are used to calculate the calm water resistance of the drillship with moonpool. The incremental change in resistance caused by the moonpool in forward motion is a measure of water motion inside the moonpool for that particular field.