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The quasi-static and dynamic mooring modules of the open-source aero-hydro-servo-elastic wind turbine simulation software, FAST v8, have previously been verified and validated, but only for mooring arrangements consisting of single lines connecting each fairlead and anchor. This paper extends the previous verification and validation efforts to focus on the multisegmented mooring capability of the FAST v8 modules: MAP++, MoorDyn, and the OrcaFlex interface. The OC3-Hywind spar buoy system tested by the DeepCwind consortium at the MARIN ocean basin, which includes a multisegmented bridle layout of the mooring system, was used for the verification and validation activities. This paper focuses on free-decay tests because the influence of the multisegmented moorings is most important for yaw motion, which is not excited by waves. All of the listed modules are able to represent the platform motion observed in the experimental data to a satisfactory degree. MoorDyn and the benchmark tool (OrcaFlex) yield almost indistinguishable results. But due to limitations of the system tested and data obtained, further work is needed to truly validate the multisegmented capability. [ABSTRACT FROM AUTHOR]

The hydrodynamic loads on an ofishore wind turbine's support structure present unique engineering challenges for offshore wind. Two typical approaches used for modeling these hydrodynamic loads are potential flow (PF) and strip theory (ST), the latter via Morison's equation. This study examines the first- and second-order wave-excitation surge forces on a fixed cylinder in regular waves computed by the PF and ST approaches to (1) verify their numerical implementations in HydroDyn and (2) understand when the ST approach breaks down. The numerical implementation of PF and ST in HydroDyn. a hydrodynamic time-domain solver implemented as a module in the FAST wind turbine engineering tool, was verified by showing the consistency in the first- and second-order force output between the two methods across a range of wave frequencies. ST is known to be invalid at high frequencies, and this study investigates where die ST solution diverges from the PF solution. Regular waves across a range of frequencies were run in HydroDyn for a monopile substructure. As expected, the solutions for the first-order (linear) wave-excitation loads resulting from these regular waves are similar for PF and ST when the diameter of the cylinder is small compared to die length of the waves (generally when the diameter-to-wavelength ratio is less man 0.2). The same finding applies to the solutions for second-order wave-excitation loads, but for much smaller dianieter-to-wavelength ratios (based on wavelengths of first-order waves). [ABSTRACT FROM AUTHOR]

The open-source, aero-hydro-servo-elastic wind turbine simulation software FAST v8 (created by the National Renewable Energy Laboratory) was recently coupled to two newly developed mooring dynamics modules: MoorDyn and FEAMooring. MoorDyn is a lumped-mass-based mooring dynamics module developed by the University of Maine, and FEAMooring is a finite-element-based mooring dynamics module developed by Texas A&M University. This paper summarizes the work performed to verify and validate these modules compared to other mooring models and measured test data to assess their reliability and accuracy. The quality of the fairlead load predictions by the open-source mooring modules MoorDyn and FEAMooring appears to be largely equivalent to that predicted by the commercial tool OrcaFlex. Both mooring dynamic model predictions agree well with the experimental data considering the given limitations in the accuracy of the platform hydrodynamic load calculation and the quality of the measurement data. [ABSTRACT FROM AUTHOR]

The article discusses research which analyzed the first phase of the Offshore Code Comparison Collaboration Continuation with Correlation project (OC5) focusing on the validation of tools for modeling offshore wind systems. Topics discussed include the validation of simulated response from various offshore wind modeling tools against tank test data and the importance of higher-order wave models in hydrodynamic load modeling.

The article identifies and analyzes the aerodynamic inflow conditions on a representative catenary moored floating offshore wind turbines (FOWT). It describes the differences and design implications for FOWT in relation to bottom-mounted and onshore wind turbines. The authors note the impact of wave induced motions on inflow conditions, such as increasing the variance of inflow velocity probability density functions.