Analysis of the Coupled Dynamics of an Offshore Floating Multi-Purpose Platform: Part A — Rigid Body Analysis

Abstract

A multi-purpose platform (MPP) is an offshore system designed to serve the purposes of more than one offshore industry. Indeed, over the past decades, a number of industries have expanded, or are expanding, from onshore to offshore locations (renewables, aquaculture, tourism, mineral extractions, etc.), and the research on these type of platform is increasing. In the present work, a MPP able to accommodate wind turbines, wave energy converters, and aquaculture systems are considered. This work presents the first part (Part A) of the analyses of the dynamics of the floating support structure for this MPP, focusing on the rigid body dynamic response, while its complementary hydroelastic analysis is presented in Part B (OMAE2019-96282). The aim here is to assess the dynamic response of the platform with respect to the preliminary requirements imposed by the wind turbine, the aquaculture system, and the other ancillary systems. After describing the platform analyzed, and explaining the aero-hydro coupled model of dynamics approach adopted, two independent analyses are conducted, one using the SESAM package by DNV-GL, and another using ANSYS AQWA, in order to verify the results, in absence of experimental data. Considering a severe, but still operational, load case, the preliminary results seem to demonstrate that the chosen platform can satisfy the dynamics constraints imposed by the payload systems.

Analysis of the Coupled Dynamics of an Offshore Floating Multi-Purpose Platform: Part B — Hydro-Elastic Analysis With Flexible Support Platform

“…The results obtained from both models support the rigid body motion approach of Ref. [8] as a reasonable first approximation of the platform behaviour, exclude the occurrence of severe resonance phenomena, and provide a useful basis for future elaborations on the coupled aero-hydro-elastic behaviour of the platform.…”

“…The floating platform considered in the present study and in Ref. [8] is a simplified draft of the full-scale configuration introduced in "The Blue Growth Farm" project and should not be taken as representative of its final design.…”

“…This issue plays a crucial role in the establishment of the platform concept, since aquaculture plants functionality and renewable energy production depends strongly on platform dynamics. This paper follows a previous one [8] (Part A), which assessed the rigid body dynamics of the platform under hydrodynamic loads. However, the hypothesis of rigid body motions made in Ref.…”

“…However, the hypothesis of rigid body motions made in Ref. [8] is potentially questioned by the overall dimensions of the platform, which are relatively large, and by the different frequency distributions of the loads, including those coming from waves and from the wind turbine, that may excite the flexible modes of the structure.…”

“…In both models, hydrodynamic added mass descends from the calculations performed in Ref. [8] and a simplified mooring system is used to obtain the desired stiffness.…”