8 results ·
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Y
youtube.com
video
https://www.youtube.com/watch?v=GGj9MxbgZek
Offshore Wind Explained E4: What are the differences of frequency domain and time domain methods?
DNV - Digital Solutions
6520 subscribers
32 likes
25330 views
18 Jul 2024
In this video, Jens Lohne Eftang, Principal Computational Scientist and technical lead for Sesam workflows for floating offshore wind, explains the differences between frequency domain and time domain methods.
Read more about time domain method here: https://www.dnv.com/article/time-domain-analysis-for-floating-offshore-wind-substructure-design/
And frequency domain method here: https://www.dnv.com/article/frequency-domain-analysis-for-floating-offshore-wind-substructure-design-251935/
As offshore structures become more complex, the computational models also become larger, leading to more expensive analyses. Choosing the right methodology for the design phase is critical, and the key is to minimize computational cost while maintaining required accuracy. This is a significant challenge for floating offshore wind substructures. We've worked closely with partners and customers to provide new solutions to this challenge.
Frequency Domain Methods
The frequency domain uncoupled method is the quickest method available in Sesam, typically used for initial sizing, early design, or prototype phases. This method involves a hydrodynamic and finite element analysis of the wave-induced structure response for specified wave directions and frequencies. It accounts for moorings and includes the wind turbine represented as a point mass, with wind loads provided by the manufacturer for fatigue (FLS) or ultimate limit state (ULS) analysis. While fast, this method has some limitations and assumptions that need consideration.
Time Domain Methods
Sesam offers three time domain workflows that balance performance and accuracy differently. In general, time domain methods are more accurate than frequency domain methods because they consider the simultaneous effects of wind and wave loading.
1. Time Domain Direct Load Generation Method: The most general method, generating hydrodynamic pressure and Morrison loads directly in the time domain before mapping them to a finite element structure. This method explores nonlinear hydrodynamic effects and dynamic local structure response, serving as a baseline for using faster methods.
2. Time Domain Load Reconstruction Method: A faster method, reconstructing pressure using results from coupled analysis combined with precomputed pressure components associated with unit waves and motions. It allows for dynamic or quasi-static local structure response but cannot include nonlinear hydrodynamic effects.
3. Time Domain Response Reconstruction Method: The fastest time domain method, reconstructing local quasi-static structure response using coupled analysis results and precomputed responses associated with unit waves, motions, and loads. This method avoids separate finite element analysis, reducing simulation time from hours to minutes for each design load case.
Chapters:
0:00-0:20 Introducing Jens Lohne Eftang
0:20-0:55Choosing the right methodology when offshore structures become more complex
0:55-01:43 The frequency domain uncoupled method
01:43-02:41 Sesam offers three time-domain workflows which in different ways balance performance and accuracy.
02:41-03:22 The Time Domain Load reconstruction method
03:22-04:28 Time Domain Response Reconstruction method
04:28-04:40 Thank you for watching
Subscribe to our channel and stay tuned: https://www.youtube.com/playlist?list=PL2EsH0WLHwsxENZGBjz8B3fBdl5Mf4RFF
#FloatingOffshoreWind #Sesam #FrequencyDomain #TimeDomain #DNV
U
upcommons.upc.edu
research
https://upcommons.upc.edu/bitstreams/54844f41-77c7-4a1f-94b7-c5f9604331ca/dow…
This paper presents an aeroelastic formulation based on the Finite Element Method (FEM) to predict the performance of an isolated horizontal axis wind turbine. Hamilton’s principle is applied to derive the equations of blade(s) aeroelasticity, based on a nonlinear beam model coupled with Beddoes-Leishman unsteady sectional aerodynamics. A devoted fifteen-degrees of freedom finite element, able to accurately model the kinematics and elastic behavior of rotating blades, is introduced and the spatial discretization of the aeroelastic equations is carried-out yielding a set of coupled nonlinear ordinary differential equations that are then solved by a time-marching algorithm. The proposed formulation may be enhanced to face the analysis of advanced blade shapes, including the presence of the tower, and represents the first step of an ongoing activity on wind energy based on a FEM approach. Due to similarities between wind turbine and helicopter rotor blades aeroelasticity, validation results firstly concern with the aeroelastic response of a helicopter rotor in hovering.
M
mdpi.com
article
https://www.mdpi.com/1996-1073/19/1/169
This study presents a frequency-domain analysis of a finite-element (FEM)-based rotor–nacelle model for wind turbines, validated against the open-source
D
dnv.com
article
https://www.dnv.com/article/time-domain-analysis-for-floating-offshore-wind-s…
# Time domain analysis for floating offshore wind substructure design. The expansion of the offshore wind industry to deeper water depths requires the usage of floating wind support structures, bringing new challenges to the industry. * Time Domain Direct Load Generation method: This is the most general method where hydrodynamic pressure and Morison loads are generated directly in the time domain before they are mapped to a structural Finite Element model. * Time Domain Load Reconstruction method: This method is an evolution of the Direct Load Generation method and can be used to drastically reduce the computational cost associated with hydrodynamic load generation. This method is the fastest and may reduce the simulation time from hours for direct simulation to just a few minutes. Frequency domain analysis for floating offshore wind substructure design. Webinar: New fast time domain simulation methods for floating wind substructure design.
R
researchgate.net
research
https://www.researchgate.net/publication/386323418_Global-Local_Finite_Elemen…
This study develops a floating offshore wind turbines (FOWTs) structural model using an efficient and accurate finite element analysis method
D
docs.nlr.gov
official
https://docs.nlr.gov/docs/fy14osti/60759.pdf
NREL is a national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Operated by the Alliance for Sustainable Energy, LLC. Contract No. DE-AC36-08GO28308 Nonlinear Legendre Spectral Finite Elements for Wind Turbine Blade Dynamics Preprint Q. Johnson Colorado School of Mines To be presented at the 32nd ASME Wind Energy Symposium National Harbor, Maryland January 13-17, 2014 Conference Paper NREL/CP-2C00-60759 January 2014 NOTICE The submitted manuscript has been offered by an employee of the Alliance for Sustainable Energy, LLC (Alliance), a contractor of the US Government under Contract No. DE-AC36-08GO28308. Sprague‡1, Jason Jonkman§1 and Nick Johnson¶2 1National Renewable Energy Laboratory, Golden, CO 80401 2Colorado School of Mines, Golden, CO 80401 This paper presents a numerical implementation and evaluation of a new nonlinear beam finite element model appropriate for highly flexible wind turbine blades made of composite materials. The underlying model uses the geometrically exact beam theory (GEBT) and spatial discretization is accomplished with Legendre spectral finite elements (LSFEs).
S
semanticscholar.org
article
https://www.semanticscholar.org/paper/Seismic-analysis-of-wind-turbines-in-th…
A computational platform for considering the effects of aerodynamic and seismic load combination for utility scale horizontal axis wind turbines · Engineering,
L
link.springer.com
article
https://link.springer.com/article/10.1186/s43088-025-00680-4
# A comprehensive review of numerical simulation techniques for wind turbines: from computational fluid dynamics and finite element analysis to advanced turbulence modeling. This review critically examines state-of-the-art numerical methodologies for the simulation of wind turbines, offering a rigorous exploration of their theoretical foundations, practical implementations, and comparative performance. The core of the study delves into advanced computational techniques encompassing computational fluid dynamics (CFD), finite element analysis (FEA), and fully coupled CFD-FEA frameworks used to resolve aerodynamic, structural, and fluid–structure interaction phenomena with high fidelity. The paper systematically analyzes turbulence modeling strategies, from industry-standard Reynolds-averaged Navier–Stokes (RANS) models to high-resolution large eddy simulation (LES) and hybrid detached eddy simulation (DES) approaches, evaluating their capabilities in capturing unsteady flow structures, vortex dynamics, and wake interactions. Through a comparative synthesis of these methods, the paper provides deep insights into their trade-offs in terms of computational cost, physical realism, and practical applicability, ultimately guiding the selection and optimization of simulation strategies for advanced wind energy system design and performance evaluation. ### A comparative study of RANS-based turbulence models for an upscale wind turbine blade.