Specification Document for OC6 Phase II: Verification of an Advanced Soil-Structure Interaction Model for Offshore Wind Turbines

Bergua, Roger; Robertson, Amy; Jonkman, Jason; Platt, Andy

doi:10.2172/1811648

Cited by 4 publications

(20 citation statements)

References 6 publications

(12 reference statements)

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“…For reference, the plots include a gray dashed line with the average result when the foundation is considered rigid (i.e., clamp at seabed), and there are no marine conditions (i.e., no water). These average results were obtained from the results provided by the participants in Load Case 2.1 (see the project definition document 12 for reference) and are aligned with the numerical values from Table 1. The black dashed line denotes the average solution when accounting for the foundation flexibility and marine conditions (i.e., still water).…”

Section: Eigenanalysis Results: Load Case 23mentioning

confidence: 70%

“…11 As noted in Section 3, the computational models account for the support structure and a lumped mass and inertia for the RNA. The wind loading in the six DOFs for Load Cases 3.1 and 5.1 (see Table 3) was computed beforehand by NREL and was applied as external force and moment time histories by participants at the yaw bearing (see the project definition document 12 for further details). Load Case 3.1 is a wind-only load case and considers a mean wind speed at hub height (V hub ) of 9.06 m/s.…”

Section: Wind-only Simulations Results: Load Case 31mentioning

confidence: 99%

“…The tower 14 is based on the offshore DTU 10-MW wind turbine design and begins at an elevation of 40 m above the seabed. The water depth is 30 m, and the monopile substructure extends from the tower base to a penetration depth of 45 m. Figure 3 provides an overview of the design, and the exact dimensions for the tower and monopile, as well as the material properties, can be found in Bergua et al 12 The eigenfrequencies of the system for a clamped condition at the seabed (and no water) can be found in Table 1. The structural damping for the first bending mode including a rigid RNA is 0.5% critical damping.…”

Section: F I G U R E 2 Global Coordinate Systemmentioning

confidence: 99%

“…The numerical values of these p-y curves are available in the project definition document. 12 The AF, CS, and DS approaches do not account for the SSI damping by default. To inform these methods, the equivalent SSI damping from the REDWIN approach was characterized at different loading levels by means of free-decay tests.…”

Section: Participant Codementioning

confidence: 99%

“…The hysteretic damping of the REDWIN approach is also nonlinear; larger amplitudes translate into larger energy dissipated. 12 Some participants decided to use some built-in capabilities in their codes to study the system. For example, Orcina uses a nonlinear hysteretic stiffness model available in OrcaFlex.…”

Section: Participant Codementioning

confidence: 99%

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OC6 Phase II: Integration and verification of a new soil–structure interaction model for offshore wind design

et al. 2021

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This paper provides a summary of the work done within the OC6 Phase II project, which was focused on the implementation and verification of an advanced soil-structure interaction model for offshore wind system design and analysis. The soil-structure interaction model comes from the REDWIN project and uses an elastoplastic, macroelement model with kinematic hardening, which captures the stiffness and damping characteristics of offshore wind foundations more accurately than more traditional and simplified soil-structure interaction modeling approaches.Participants in the OC6 project integrated this macroelement capability to coupled aero-hydro-servo-elastic offshore wind turbine modeling tools and verified the implementation by comparing simulation results across the modeling tools for an example monopile design. The simulation results were also compared to more traditional soil-structure interaction modeling approaches like apparent fixity, coupled springs, and distributed springs models. The macroelement approach resulted in smaller overall loading in the system due to both shifts in the system frequencies and increased energy dissipation. No validation work was performed, but the macroelement approach has shown increased accuracy within the REDWIN project, resulting in decreased uncertainty in the design. For the monopile design investigated here, that implies a less conservative and thus more cost-effective offshore wind design.

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Section: Eigenanalysis Results: Load Case 23mentioning

confidence: 70%

Section: Wind-only Simulations Results: Load Case 31mentioning

confidence: 99%

Section: F I G U R E 2 Global Coordinate Systemmentioning

confidence: 99%

Section: Participant Codementioning

confidence: 99%

Section: Participant Codementioning

confidence: 99%

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OC6 Phase II: Integration and verification of a new soil–structure interaction model for offshore wind design

et al. 2021

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OC6 Phase IV: Validation of CFD Models for Stiesdal TetraSpar Floating Offshore Wind Platform

Darling,

Schmidt,

Xie

et al. 2024

Wind Energy

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With only a few floating offshore wind turbine (FOWT) farms deployed anywhere in the world, FOWT technology is still in its infancy, building on a modicum of real‐world experience to advance the nascent industry. To support further development, engineers rely heavily on modeling tools to accurately portray the behavior of these complex systems under realistic environmental conditions. This reliance creates a need for verification and validation of such tools to improve reliability of load and dynamic response prediction and analysis capabilities of FOWT systems. The Offshore Code Comparison Collaboration, Continued with Correlation and unCertainty (OC6) project was created under the framework of the International Energy Agency to address this need and considers a three‐sided verification and validation between engineering level models, computational fluid dynamics (CFD), and experimental results. In this paper, a novel floating offshore wind platform, the Stiesdal TetraSpar, is simulated using CFD under the load conditions defined by Phase IV of the OC6 project. The comparison of these CFD results against the experimental results demonstrated the ability to predict the platform response to waves when imposing the measured wave signals as input. Although validation versus experiment was largely successful, the damping behavior was impacted by uncertainties likely originating from the mooring system and sensor umbilical cable. This extensive comparison effort with multiple CFD practitioners offers insight into best practices to achieve reliable results.

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Fatigue life evaluation of offshore wind turbines considering scour and passive structural control

Cao,

Wu,

Yang

et al. 2023

Preprint

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Abstract. Offshore wind turbine (OWT) support structures are exposed to the risk of fatigue damages and scour, and this risk can be effectively mitigated by installing structural control devices such as tuned mass dampers (TMDs). However, time-varying scour altering OWTs’ dynamic characteristics has an impact on the TMD design and fatigue life, which was rarely studied before. In this paper, a simplified modal model was used to investigate the influence of scour and a TMD on the fatigue life evaluation of a 5 MW OWT’s support structure, and the parameters of the TMD were obtained by either a traditional method or a newly developed optimization technique. This optimization technique aims at finding optimal parameters of the TMD which maximizes the fatigue life of a hotspot at the mudline, and effect of time-varying scour can be considered. Results show that scour can decrease the fatigue life by about 26 %, and the TMD can effectively suppress vibration and increase the fatigue life. Further, it is found that the fatigue life can be extended by 7.2 % with the TMD optimized by the proposed optimization technique, compared to that with the traditionally optimized TMD which does not take the change of dynamic characteristics into account.

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Specification Document for OC6 Phase II: Verification of an Advanced Soil-Structure Interaction Model for Offshore Wind Turbines

Abstract: Department of Energy (DOE) reports produced after 1991 and a growing number of pre-1991 documents are available free via www.OSTI.gov.

Cited by 4 publications

References 6 publications

OC6 Phase II: Integration and verification of a new soil–structure interaction model for offshore wind design

OC6 Phase II: Integration and verification of a new soil–structure interaction model for offshore wind design

OC6 Phase IV: Validation of CFD Models for Stiesdal TetraSpar Floating Offshore Wind Platform

Fatigue life evaluation of offshore wind turbines considering scour and passive structural control

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