Analysis on Motions and Green Water of FPSOs in Shallow Water With Non-Collinear Environments

Abstract

The paper presents motions and green water of a FPSO in shallow water with different wave headings. In non-collinear directions of wind, waves and current, the FPSO does not always encounter head waves, which probably induces specialties in motions and green water especially because of the complexity of shallow water hydrodynamics. Time-domain numerical simulation and model test are carried out in order to analyze motions of a single-point moored FPSO. Green water and wave run-up along the side of a fixed FPSO are simulated in a 3-D numerical wave tank, and results are compared with that of model tests. It is shown that the influence of the yaw angle on motions of a FPSO is considerable and green water occurs more frequently around the mid-ship when the FPSO encounters a big wave heading. In the same water depth, roll and pitch motions of the FPSO under higher wave are lower instead but green water occurs; in the same wave situation, the motions of the FPSO in a lower water depth are lower, but green water occurs more severely. In general, water depth has an important influence on green water of FPSOs in shallow water. The hydrodynamic character of large floating structures in shallow water, especially the green water, should be taken into account carefully for determining the design load and freeboard of a large floating structure.