Numerical studies on CALM buoy motion responses and the effect of buoy geometry cum skirt dimensions with its hydrodynamic waves-current interactions

Abstract

An essential aspect of Catenary Anchor Leg Moorings (CALM) buoy structures are the components of hydrodynamics like waves, underwater current, and wind. In this study, numerical investigations on CALM buoy were carried out. Firstly, motion study of free-floating CALM buoy was conducted in ANSYS AQWA. Then an Orcaflex-coupled model of the CALM buoy system with submarine hoses in Lazy-S configuration, was presented. It was attached to six mooring lines under 100 m water depth. Two types of buoy geometries have been investigated: Square Buoy (SB) and the Cylindrical Buoy (CB). Different cases with the same buoy widths were considered using three buoy skirts at 13.90m, 12.90m, and 11.90m. Diffraction analysis was used to obtain the motion behaviour. Results on the CALM buoy motion responses in six degrees of freedom (6DoF) like surge and heave motions, response amplitude operators (RAOs), radiation damping, and added mass, were also presented. The buoy geometry and skirt both influence its hydrodynamics. The study successfully achieved good reports on motion characteristics and wave-current interaction (WCI) for CALM buoys.