Time-Domain Response-Based Structural Analysis on a Floating Offshore Wind Turbine

Abstract

As the turbine blade size becomes larger for economic power production, the coupling effect between wind turbine and floating substructure becomes important in structural assessment. Due to unsteady turbulent wind environment and corresponding coupled substructure response, time-domain analysis is required by international electrotechnical commission and class societies. Even though there are a few numerical tools available for the time domain structural analysis based on conventional coupled motion analysis with wind turbine, the application of conventional time domain analysis is impractical and inefficient for structural engineers and hull designers to perform structural strength and fatigue assessment for the required large number of design load cases since it takes huge simulation time and computational resources. Present paper introduces an efficient time-domain structural analysis practically applicable to buckling and ultimate strength assessment. Present method is based on ‘lodal’ response analysis and pseudo-spectral stress synthesizing technique, which makes timedomain structural analysis efficient and practical enough to be performed even in personal computing system. Practical buckling assessment methodology is also introduced applicable to the time-domain structural analyses. For application of present method, a 15-MW floating offshore wind turbine platform designed for Korean offshore wind farm projects is applied. Based on full-blown time domain structural analysis for governing design load cases, buckling and ultimate strength assessments are performed for the extreme design environments, and the class rule provided by Korean Register is checked.

Keywords

Time domain / Structural analysis / Lodal response / Floating wind turbine / Buckling and strength analysis

References

[1] ABS (2020a) Guide for building and classing — Floating offshore wind turbines. American Bureau of Shipping

[2] ABS (2020b) Global performance analysis for floating offshore wind turbines. Guidance notes, American Bureau of Shipping

[3] ABS (2022a) Rules for building and classing-Floating production installations. American Bureau of Shipping

[4] ABS (2022b) Rules for building and classing — Mobile offshore drilling units. American Bureau of Shipping

[5] API Recommended practice for planning, designing and constructing fixed offshore platforms-working stress design, 2000, Washington, DC: American Petroleum Institute, API-RP-2A-WSD

[6] API Recommended practice for planning, designing, and constructing floating production systems, 2011, Washington, DC: American Petroleum Institute, API-RP-2FPS

[7] API Recommended practice for planning, designing, and constructing tension leg platforms, 2015, Washington, DC: American Petroleum Institute, API-RP-2T

[8] DNV Buckling, 2015, Oslo: Det Norske Veritas, DNVGL-CG-0128

[9] DNV Structural design of offshore Units-WSD method, 2017, Oslo: Det Norske Veritas, DNV-OS-C201

[10] DNV Floating wind turbine structures, 2021, Oslo: Det Norske Veritas, DNV-ST-0119

[11] IACS Common structural rule for bulk carriers and oil tankers, 2022, London: International Association of Classification Societies

[12] IEC Wind turbines-Part 1: Design requirements, 2005, Geneva: International Electrotechnical Commission, International standard, IEC-61400-1

[13] IEC Wind energy generation systems-Part 3-1: Design requirements for fixed offshore wind turbines, 2019, Geneva: International Electrotechnical Commission, Technical Specification, IEC-61400-3-1

[14] IEC Wind energy generation systems — Part 3-2: Design requirements for floating offshore wind turbines, 2019, Geneva: International Electrotechnical Commission, Technical Specification, IEC-61400-3-2

[15] Kim KH, Park SW, Ha YJ, Lee HT, Shen Z, Kyoung JH, Kim JW (2022) Development of 15MW floating offshore wind turbine substructure customized to Korean shipyards. 4th International Offshore Wind Technical Conference, Boston, IOWTC2022-96596

[16] Korean Register Guidance for floating structures, 2010, Busan: Korean Register of Shipping

[17] Korean Register Rules for classification of steel ships-Part 3: Hull structures, 2021, Busan: Korean Register of Shipping

[18] Kyoung JH, Samaria S, Kim JW, Duffy B (2019) Response based time domain structural analysis on floating offshore platform. 38th International Conference on Ocean, Offshore and Arctic Engineering, Glasgow, OMAE2019-96139

[19] Kyoung JH, Samaria S, Kim JW (2020) Time domain structural fatigue analysis of floating offshore platforms: A response based technique. 39th International Conference on Ocean, Offshore and Arctic Engineering, OMAE2020-18314

[20] Kyoung JH, Samaria S, O’Donnell J, Tallavajhula S (2021) Advances in offshore structural analysis using response-based time-domain approach. Offshore Technology Conference, OTC-31280-MS