Effect of the Moonpool on the Total Resistance of a Drillship

Abstract

Open moonpools in a drillship is causing additional resistance when the ship is in transit. In previous studies found in literature the resistance increase and the flow behavior has been investigated both with the help of commercial CFD programs but mainly through model tests. It was shown that the water inside the moonpool started to oscillate at forward speed. Two types of oscillation modes, piston and sloshing, has shown to be apparent where sloshing was dominant in longer moonpools and piston in shorter. The amplitude is correlated with the forward speed such that increased forward speed leads to increased amplitudes. In this thesis the behavior of the flow has been investigated by open source Computational Fluid Dynamic (CFD) software OpenFOAM and a two-dimensional case was set up. For validation, simulations have been carried out on similar models as used in a model test conducted by SAMSUNG Heavy Industries CO LTD (SHI). The method described in this thesis is a good tool for getting an understanding of the flow behavior and can be used in an early design stage of a moonpool. Results in this report shows that the flow pattern is consistent between model tests and the numerical solution, but it has not been possible to show trends for the resistance in two dimensions.