Total experimental uncertainty in hydrodynamic testing of a semisubmersible wind turbine, considering numerical propagation of systematic uncertainty

Robertson, Amy; Bachynski, Erin Elizabeth; Gueydon, Sébastien; Wendt, Fabian; Schünemann, Paul

doi:10.1016/j.oceaneng.2019.106605

Cited by 50 publications

(36 citation statements)

References 4 publications

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“…The variation in the results is significant and may be due to both intentional and unintentional actions. Recent work focused on quantifying the uncertainty in the experimental results, to try to better understand the discrepancies, suggests that the differences between simulations and experiments are larger than the experimental uncertainties [148][149][150]. Comparisons against full-scale data have also shown large discrepancies; however, the reasons for these discrepancies are more difficult to discern: difficulties in obtaining information about the exact wind and wave conditions, yaw misalignment, or details of the control system, contribute in addition to limitations in the software or user error [151].…”

Section: Account Of Uncertaintiesmentioning

confidence: 99%

Recent Advances in Integrated Response Analysis of Floating Wind Turbines in a Reliability Perspective

Moan

Gao

Bachynski

et al. 2020

Journal of Offshore Mechanics and Arctic Engineering

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Offshore wind provides an important source of renewable energy. While wind turbines fixed to the seabed in shallow water have already been industrialized, floating wind turbines are still at an early stage of development. The cost of wind power is decreasing fast. Yet, the main challenges, especially for novel floating wind turbine concepts, are to increase reliability and reduce costs. The reliability perspective here refers to the lifecycle integrity management of the system to ensure reliability by actions during design, fabrication, installation, operation, and decommissioning. The assessment should be based on response analysis that properly accounts for the effect of different sub-systems (rotor, drivetrain, tower, support structure, and mooring) on the system behavior. Moreover, the load effects should be determined so as to be proper input to the integrity check of these sub-systems. The response analysis should serve as the basis for design and managing inspections and monitoring, with due account of inherent uncertainties. In this paper, recent developments of methods for numerical and experimental response assessment of floating wind turbines are briefly described in view of their use to demonstrate system integrity in design as well as during operation to aid inspection and monitoring. Typical features of offshore wind turbine behavior are also illustrated through some numerical case studies.

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Section: Account Of Uncertaintiesmentioning

confidence: 99%

Recent Advances in Integrated Response Analysis of Floating Wind Turbines in a Reliability Perspective

Moan

Gao

Bachynski

et al. 2020

Journal of Offshore Mechanics and Arctic Engineering

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“…Because of the engineering importance of hydrodynamic damping in the design of floating offshore structures, extensive research exists on this subject, including studies that are based on the same DeepCwind semisubmersible design used in the Offshore Code Comparison Collaboration Continuation (OC4 [6]), Offshore Code Comparison Collaboration, Continued with Correlation (OC5 [7,8]), and OC6 projects [9,10] (Note that across these projects, the geometry of the semisubmersible has not changed, but the mass and inertia properties were modified to address small changes in the design of the wind turbine it supported).…”

Section: Introductionmentioning

confidence: 99%

“…Li and Bachynski-Polić [17] investigated the low-frequency radiation characteristics of the OC6-DeepCwind floater [9,10] by simulating free-decay motions and forced oscillation in surge, heave, and pitch. The heave and pitch decay from the CFD simulations were generally consistent with the experimental measurements, but the surge decay showed substantial differences, with the OC6 experiment having much faster decay.…”

Section: Introductionmentioning

confidence: 99%

OC6 Phase Ia: CFD Simulations of the Free-Decay Motion of the DeepCwind Semisubmersible

et al. 2022

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Currently, the design of floating offshore wind systems is primarily based on mid-fidelity models with empirical drag forces. The tuning of the model coefficients requires data from either experiments or high-fidelity simulations. As part of the OC6 (Offshore Code Comparison Collaboration, Continued, with Correlation, and unCertainty (OC6) is a project under the International Energy Agency Wind Task 30 framework) project, the present investigation explores the latter option. A verification and validation study of computational fluid dynamics (CFD) models of the DeepCwind semisubmersible undergoing free-decay motion is performed. Several institutions provided CFD results for validation against the OC6 experimental campaign. The objective is to evaluate whether the CFD setups of the participants can provide valid estimates of the hydrodynamic damping coefficients needed by mid-fidelity models. The linear and quadratic damping coefficients and the equivalent damping ratio are chosen as metrics for validation. Large numerical uncertainties are estimated for the linear and quadratic damping coefficients; however, the equivalent damping ratios are more consistently predicted with lower uncertainty. Some difference is observed between the experimental and CFD surge-decay motion, which is caused by mechanical damping not considered in the simulations that likely originated from the mooring setup, including a Coulomb-friction-type force. Overall, the simulations and the experiment show reasonable agreement, thus demonstrating the feasibility of using CFD simulations to tune mid-fidelity models.

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“…A porous disk model has some inherent limitations: it is not valid to study the near wake and does not reproduce the local aerodynamic loads of blades. One goal of the EU H2020 LIFES50+ project was to develop a reliable aerodynamic model of an FOWT rotor to be used in hybrid wave-basin experiments (a numerical rotor is coupled to a physical scale model of the floating platform, as done by Sauder et al, 2016). For this purpose, Bayati et al (2016) investigated the effect of imposed surge and pitch motion on rotor thrust with a 1/75 scale model of the DTU 10 MW.…”

Section: Introductionmentioning

confidence: 99%

UNAFLOW: a holistic wind tunnel experiment about the aerodynamic response of floating wind turbines under imposed surge motion

et al. 2021

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Abstract. Floating offshore wind turbines are subjected to large motions due to the additional degrees of freedom of the floating foundation. The turbine rotor often operates in highly dynamic inflow conditions, and this has a significant effect on the overall aerodynamic response and turbine wake. Experiments are needed to get a deeper understanding of unsteady aerodynamics and hence leverage this knowledge to develop better models and to produce data for the validation and calibration of existing numerical tools. In this context, this paper presents a wind tunnel experiment about the unsteady aerodynamics of a floating turbine subjected to surge motion. The experiment results cover blade forces, rotor-integral forces, and wake. The 2D sectional model tests were carried out to characterize the aerodynamic coefficients of a low-Reynolds-number airfoil with harmonic variation in the angle of attack. The lift coefficient shows a hysteresis cycle close to stall, which grows in strength and extends in the linear region for motion frequencies higher than those typical of surge motion. Knowledge about the airfoil aerodynamic response was utilized to define the wind and surge motion conditions of the full-turbine experiment. The global aerodynamic turbine response is evaluated from rotor-thrust force measurements, because thrust influences the along-wind response of the floating turbine. It is found that experimental data follow predictions of quasi-steady theory for reduced frequency up to 0.5 reasonably well. For higher surge motion frequencies, unsteady effects may be present. The turbine near wake was investigated by means of hot-wire measurements. The wake energy is increased at the surge frequency, and the increment is proportional to the maximum surge velocity. A spatial analysis shows the wake energy increment corresponds with the blade tip. Particle image velocimetry (PIV) was utilized to visualize the blade-tip vortex, and it is observed that the vortex travel speed is modified in the presence of surge motion.

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Total experimental uncertainty in hydrodynamic testing of a semisubmersible wind turbine, considering numerical propagation of systematic uncertainty

Cited by 50 publications

References 4 publications

Recent Advances in Integrated Response Analysis of Floating Wind Turbines in a Reliability Perspective

Recent Advances in Integrated Response Analysis of Floating Wind Turbines in a Reliability Perspective

OC6 Phase Ia: CFD Simulations of the Free-Decay Motion of the DeepCwind Semisubmersible

UNAFLOW: a holistic wind tunnel experiment about the aerodynamic response of floating wind turbines under imposed surge motion

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