Component Approach for Confident Predications of Deepwater CALM Buoy Coupled Motions: Part 2 — Analytical Implementation

Abstract

This paper describes an analytical implementation of the component approach for motion predictions of a deepwater CALM buoy as described in the companion paper “Component Approach for Confident Predictions of Deepwater CALM Buoy Coupled Motions — Part 1: Philosophy”. The implementation of the approach starts with a “model-of-the-model” validation of the analytical tool. Emphasis is given to making an accurate analytical characterization of the model as tested. To capture the strong coupling between the buoy motions and line dynamics the analyses described herein were carried out in the time-domain. This allows a rigorous treatment of the hydrodynamic forces on the buoy as well as the non-linear mooring loads when analyzing the buoy responses in waves. Since the validation analysis is a model-of-the-model practice at model scale, the proper application of the validated tool to the full-scale system is discussed. This involves modeling of the exact full-scale system and the proper selection of the hydrodynamic coefficients for the buoy and lines. In this paper we will present the numerical modeling procedures and the results from validation work to confirm that the analytical tool is validated correctly. Detailed results from validation analysis versus model test data will be shown for system components including buoy hydrodynamics from the forced oscillation test, line tension from line oscillation test, and the motions and tensions of integrated buoy/mooring/riser system. We point out that the hydrodynamic coefficients at model scale can not be directly applied to the full-scale system analysis even though they are from model test measurements. We will present the difference between the results of the model-scale system using model scale hydrodynamic coefficients and those based on a proper range of the coefficients at full-scale. This will highlight the need to design component tests to determine appropriate full scale coefficients in order to improve the accuracy of full-scale design predictions. These results will show the advantages of adopting a component approach over the common industry practices in the areas of correct use of model test data, validation analysis and the analysis of the coupled CALM buoy system responses in waves.

An Investigation on the Vortex Effect of a CALM Buoy under Water Waves Using Computational Fluid Dynamics (CFD)

“…In such instance, their contribution to total drag is included in the drag loads on the skirt in the study presented here, which could lead to an overestimation of the CD values. Recent applications have been conducted by coupling CALM buoy models using related hydrodynamic formulations in literature [78][79][80][81]. .…”

An Overview on Bonded Marine Hoses for Sustainable Fluid Transfer and (Un)Loading Operations via Floating Offshore Structures (FOS)

“…Different studies have been conducted on the numerical modelling of hose-mooring systems for marine hoses [46][47][48][49][50][51][52][53][54][55][56], CALM buoys [57][58][59][60][61][62][63][64][65][66][67], and offloading systems [68][69][70][71][72][73][74][75][76][77][78]. Most studies on marine hoses does not include mooring line safety ([36,37,42-45,79-88]).…”

Numerical Assessment on the Dynamic Behaviour of Submarine Hoses Attached to CALM Buoy Configured as Lazy-S under Water Waves

“…The mathematical formulation for the hose model was developed based on the problem, some simplifications, the author s experimental cum numerical findings [36][37][38][39][40], and some known offshore engineering practices on submarine hoses [45][46][47]. The seabed under consideration is horizontal and rigid, and the hose s material is isotropic and elastic.…”

“…Figure 1 represents a sketch of a CALM buoy system with submarine hoses attached using Lazy-S configuration under operation. The coupled analysis of CALM buoy has also been studied on elastic seabeds [46][47][48][49][50][51][52][53], but none were reported on the nonlinear seabed. The application of nonlinear seabed profiles has been considered on other offshore structures [54,55].…”