Session: Hydrodynamic and Coupled Analyses-1

Paper Number: 163672

163672 - Guidelines for Fowt Support Structure Design Assessment 

Abstract: 

Floating offshore wind energy is rapidly advancing towards large-scale industrial deployment. In designing floating offshore wind farms, numerical calculations encompassing Integrated Load Analysis (or coupled analyses) and structural analyses of each component (floater hull, tower, wind turbine) are crucial, particularly for design and certification purposes.

Currently, recognized technical standards used for floating offshore wind turbines (FOWT) design assessments combine elements both from wind turbine industry and offshore Oil and Gas industry, notably from the IEC 61400 series, ISO 19900 series and classification society rules and guidelines. Consequently, the design assessment calculation process - consisting of (i) environmental condition derivation and design load cases, (ii) load analyses, and (iii) further analyses for each design criterion (e.g. structural analyses) - is not straightforward, non-standardized, and prone to misinterpretation. This typically leads to long design assessment periods and suboptimal allocation of computation resources, often resulting in excessive effort on certain aspects while neglecting critical methodological elements for a reliable design.

This paper presents Bureau Veritas’ (BV) new guidelines for FOWT design assessments calculations. The topics covered include (i) metocean conditions derivations and consistent design load cases and calculation cases derivations, (ii) Integrated Load Analysis for the different design verifications (structure, stationkeeping system, etc…), and (iii) floating substructure structural analysis. The focus is on developing consistent workflows to ensure all critical physical phenomena impacting calculation results are considered, while balancing accuracy and computational efficiency.

Additionally, key assumptions and objectives of each calculation step are highlighted. Rather than prescribing a unique approach to perform these calculations, these guidelines aim to offer the industry a coherent framework based on BV's experience and lessons learned in FOWT project certification and state-of-the-art FOWT calculation software development. Consequently, a review of the different possible options is presented with challenges, pros and cons.

The paper is structured in three parts. In a first part, a consistent methodology for obtention of environmental conditions and definition of environmental cases combinations for the different design load cases (DLC) is presented. The major challenge relies on that this step is typically performed by different actors (metocean specialist on one side, designers on the other side), and consistency is not always reached. In a second part, workflows and relevant assumptions for aero-hydro-servo-elastic modelling of FOWT are presented. The main original contribution is how the different design verifications are considered at this stage. It also includes details on how the modal analysis of the coupled system is integrated to the load analysis models. In a third part, supplementary analyses that build upon load analysis results are considered. The focus is on floating substructure structural analysis and associated structure code checks, notably on critical aspects such as load transfer.

This work contributes to standardization and optimization of the design calculations process for floating offshore wind farms.

Presenting Author: Vincent Arnal Bureau Veritas

Presenting Author Biography: Vincent holds a Master's degree in Naval Architecture (2014) and a Ph.D. in Fluid Mechanics (2020), both from Ecole Centrale de Nantes. His academic career at the LHEEA laboratory of Ecole Centrale Nantes involved contributions to various R&D projects, focusing on numerical and experimental modeling of Floating Offshore Wind Turbines (FOWTs).
Vincent gained valuable industry experience in FOWT coupled calculations while working for a floater designer. In 2021, he joined Bureau Veritas Marine & Offshore, where he currently leads the development of rules and guidelines for FOWTs and other marine renewable energy technologies. His expertise extends to international standardization efforts, actively participating in IEC working groups.

Authors:

Vincent Arnal Bureau Veritas
Jérôme De Lauzon Bureau Veritas Marine & Offshore
Cédric Brun Bureau Veritas Marine & Offshore