OC6 Phase Ib: Floating Wind Component Experiment for Difference-Frequency Hydrodynamic Load Validation

Abstract

A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue loading in semisubmersible designs. A component-level approach was taken to examine the hydrodynamic loads on individual parts of the semisubmersible in isolation and then in the presence of other members to assess the change in hydrodynamic loading. A variety of wave conditions were investigated, including bichromatic waves, to provide a direct assessment of difference-frequency wave loading. An assessment of the impact of wave uncertainty on the loading was performed, with the goal of enabling validation with this dataset of numerical models with different levels of fidelity. The dataset is openly available for public use and can be downloaded from the U.S. Department of Energy Data Archive and Portal.

Numerical Assessment of a Tension-Leg Platform Wind Turbine in Intermediate Water Using the Smoothed Particle Hydrodynamics Method

“…A stretched algorithm as described in [76] is used to define the spectral bandwidth discretization so that many more frequency components are representative of the most energyrich part of the spectrum. The said internal tool for the time series generation allows for the definition of seed numbers that are used for the generation of the uniform distribution of φ i to be plugged into (15).…”

“…Energies 2022, 15,3993 the distance between the wavemaker and the TLP is set to 6.00 m for both cases in Table 2. The piston motion is computed by an internal routine according to the parameters presented in Table 2, and corrected in time by an AWAS system.…”

“…High-fidelity modeling procedures to solve the dynamics of the system are indeed necessary to obtain reliable model results [14]. It is interesting to mention that, although the main focus of certain research projects, such as the OC6 (Offshore Code Comparison, Collaboration, Continued, with Correlation and unCertainty), is on the validation of engineering-design tools for offshore wind turbines, the latest testing campaign outcome of Phase Ib [15] has a broader scope and is suitable for CFD code validation.…”

OC6 Phase Ia Definition Document: Validation of Nonlinear Hydrodynamic Loading on the DeepCwind Semisubmersible

“…An additional validation campaign, which focused on the components of this system, was completed in 2021 to further analyze the low-frequency issue and was named OC6 Phase Ib. Information on this project can be found in (Robertson et al 2021).…”

On the use of constrained focused waves for characteristic load prediction

“…The low frequency contribution around approximately 0.05Hz is caused by the low frequency surge motion. These low frequency motions of semisubs have been the subject of much study in recent years as the majority of numerical models have failed to replicate them(Robertson et al (2020),Robertson & Wang (2021)). For surge and therefore the mooring load, this was found to be due to so called viscous drift(Ma et al 2020) which is a third order effect due to drag(Wang et al 2022), primarily above the mean…”