Fully-Coupled Aero-Hydrodynamic Simulation of Floating Offshore Wind Turbines by Different Simulation Methods

2018 ◽  
Author(s):  
Ping Cheng ◽  
Decheng Wan
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Hydrodynamic Simulation ◽  
Floating Offshore Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Fully Coupled

To accurately predict the critical loads due to wind and wave is one of the common challenges in designing a floating offshore wind turbine (FOWT). The fully-coupled aero-hydrodynamic simulation of a floating offshore wind turbine, the NREL-5MW baseline wind turbine mounted on a semi-submersible floating platform, is conducted with two methods. Firstly, the in-house code naoe-FOAM-os-SJTU, which is developed on the open source platform OpenFOAM and coupled with the overset grid technique, is employed for the directly CFD computations. And another in-house code FOWT-UALM-SJTU developed by coupling the unsteady actuator line model (UALM) with naoe-FOAM-SJTU is also utilized for coupling simulations. In both models, the three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are solved with the turbulence model k-ω SST, and the Pressure-Implicit with Splitting of Operations (PISO) algorithm is applied to solve the pressure-velocity coupling equations. Both two solvers provide reasonable results of main aerodynamic loads as well as the main hydrodynamic forces. The FOWT-UALM-SJTU solver achieves better computational efficiency by simplifying the blade structure as actuator line models, while the naoe-FOAM-os-SJTU solver provides more accurate detailed flow information near the turbine blades.

Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions

2015 ◽  
Author(s):  
H. K. Jang ◽  
H. C. Kim ◽  
M. H. Kim ◽  
K. H. Kim
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Random Waves ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine ◽  
Coupled Dynamic Analysis ◽  
Floating Offshore Wind Turbines

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects. In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios. In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.

Individual Blade Pitch Control for Alleviation of Vibratory Loads on Floating Offshore Wind Turbines

2021 ◽  
Author(s):  
Luca Pustina ◽  
Claudio Pasquali ◽  
Jacopo Serafini ◽  
Claudio Lugni ◽  
Massimo Gennaretti
Keyword(s):  
Renewable Energy ◽  
Wind Turbine ◽  
Bending Moment ◽  
Offshore Wind ◽  
Synthesis Process ◽  
Control Synthesis ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Blade Root ◽  
Floating Offshore Wind Turbines

Abstract Among the renewable energy technologies, offshore wind energy is expected to provide a significant contribution for the achievement of the European Renewable Energy (RE) targets for the next future. In this framework, the increase of generated power combined with the alleviation of vibratory loads achieved by application of suitable advanced control systems can lead to a beneficial LCOE (Levelized Cost Of Energy) reduction. This paper defines a control strategy for increasing floating offshore wind turbine lifetime through the reduction of vibratory blade and hub loads. To this purpose a Proportional-Integral (PI) controller based on measured blade-root bending moment feedback provides the blade cyclic pitch to be actuated. The proportional and integral gain matrices are determined by an optimization procedure whose objective is the alleviation of the vibratory loads due to a wind distributed linearly on the rotor disc. This control synthesis process relies on a linear, state-space, reduced-order model of the floating offshore wind turbine derived from aero-hydroelastic simulations provided by the open-source tool OpenFAST. In addition to the validation of the proposed controller, the numerical investigation based on OpenFAST predictions examines also the corresponding control effort, influence on platform dynamics and expected blade lifetime extension. The outcomes show that, as a by-product of the alleviation of the vibratory out-of-plane bending moment at the blade root, significant reductions of both cumulative blade lifetime damage and sway and roll platform motion are achieved, as well. The maximum required control power is less than 1% of the generated power.

Dynamic Modeling and Simulation of a Spar Floating Offshore Wind Turbine With Consideration of the Rotor Speed Variations

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Mohammed Khair Al-Solihat ◽  
Meyer Nahon ◽  
Kamran Behdinan
Keyword(s):  
System Dynamics ◽  
Wind Turbine ◽  
Torque Control ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Aerodynamic Load ◽  
Floating Platform ◽  
Dynamic Simulations ◽  
Floating Offshore Wind Turbine ◽  
Wind Turbine Tower

This paper presents a rigid multibody dynamic model to simulate the dynamic response of a spar floating offshore wind turbine (FOWT). The system consists of a spar floating platform, the moorings, the wind turbine tower, nacelle, and the rotor. The spar platform is modeled as a six degrees-of-freedom (6DOFs) rigid body subject to buoyancy, hydrodynamic and moorings loads. The wind turbine tower supports rigid nacelle and rotor at the tip. The rigid rotor is modeled as a disk spinning around its axis and subject to the aerodynamic load. The generator torque control law is incorporated into the system dynamics to capture the rotor spinning speed response when the turbine is operating below the rated wind speed. The equations of motions are derived using Lagrange's equation in terms of the platform quasi-coordinates and rotor spin speed. The external loads due to hydrostatics, hydrodynamics, and aerodynamics are formulated and incorporated into the equations of motion. The dynamic simulations of the spar FOWT are performed for three load cases to examine the system eigen frequencies, free decay response, and response to a combined wave and wind load. The results obtained from the present model are validated against their counterparts obtained from other simulation tools, namely, FAST, HAWC2, and Bladed, with excellent agreement. Finally, the influence of the rotor gyroscopic moment on the system dynamics is investigated.

Structural Control of an Ultra-Large Semi-Submersible Floating Offshore Wind Turbine

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Zhixin Zhao ◽  
Wenhua Wang ◽  
Dongdong Han ◽  
Wei Shi ◽  
Yulin Si ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Dynamic Model ◽  
Structural Control ◽  
Degrees Of Freedom ◽  
Vibration Suppression ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine ◽  
Proposed Model

Abstract A braceless semi-submersible floating platform is proposed for a Technical University of Denmark (DTU) 10-MW wind turbine at moderate water depths with reference to an existing National Renewable Energy Laboratory (NREL) 5-MW braceless semi-submersible floating platform, and a servo control system for a 10-MW semi-submersible floating offshore wind turbine (FOWT) is introduced. To control the ultimate and fatigue loads of the FOWT, a fore-aft tuned mass damper (TMD) installed in the nacelle of the 10-MW semi-submersible FOWT was investigated for vibration alleviation and load reduction. Considering the hydrodynamic and mooring effect, a four degrees-of-freedom (DOFs) (platform surge and pitch motions, tower fore-aft bending, and TMD translation) simplified dynamic model for the 10-MW semi-submersible FOWT is established based on D’Alembert’s principle. Then, the parameter estimation is conducted based on the Levenberg–Marquardt (LM) algorithm, and the simplified dynamic model was further verified by comparing the output responses with FAST and the proposed model. Furthermore, the exhaustive search (ES) and genetic algorithm (GA) are embedded into the simplified dynamic model to optimize the TMD parameters. Finally, a fully coupled time-domain simulation for all the selected environmental conditions is conducted in FAST, and the vibration suppression performance of the optimized TMD design for the 10-W semi-submersible FOWT was further examined and analyzed.

Dynamic Responses of a Spar Type Floating Offshore Wind Turbine With Failed Moorings

2020 ◽  
Author(s):  
Yajun Ren ◽  
Vengatesan Venugopal
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Floating Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Platform Motions

Abstract The complex dynamic characteristics of Floating Offshore Wind Turbines (FOWTs) have raised wider consideration, as they are likely to experience harsher environments and higher instabilities than the bottom fixed offshore wind turbines. Safer design of a mooring system is critical for floating offshore wind turbine structures for station keeping. Failure of mooring lines may lead to further destruction, such as significant changes to the platform’s location and possible collisions with a neighbouring platform and eventually complete loss of the turbine structure may occur. The present study focuses on the dynamic responses of the National Renewable Energy Laboratory (NREL)’s OC3-Hywind spar type floating platform with a NREL offshore 5-MW baseline wind turbine under failed mooring conditions using the fully coupled numerical simulation tool FAST. The platform motions in surge, heave and pitch under multiple scenarios are calculated in time-domain. The results describing the FOWT motions in the form of response amplitude operators (RAOs) and spectral densities are presented and discussed in detail. The results indicate that the loss of the mooring system firstly leads to longdistance drift and changes in platform motions. The natural frequencies and the energy contents of the platform motion, the RAOs of the floating structures are affected by the mooring failure to different degrees.

Coupled Numerical Analysis of a Concept TLB Type Floating Offshore Wind Turbine

2019 ◽  
Author(s):  
Iman Ramzanpoor ◽  
Martin Nuernberg ◽  
Longbin Tao
Keyword(s):  
Wind Turbine ◽  
Renewable Energy Sources ◽  
Second Order ◽  
Offshore Wind ◽  
Design Stage ◽  
Offshore Wind Turbine ◽  
Clear Understanding ◽  
Mooring System ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine

Abstract The main drivers for the continued decarbonisation of the global energy market are renewable energy sources. Moreover, the leading technological solutions to achieve this are offshore wind turbines. As installed capacity has been increasing rapidly and shallow water near shore sites are exhausted, projects will need to be developed further from shore and often in deeper waters, which will pose greater technical challenges and constrain efforts to reduce costs. Current floating platform solutions such as the spar and semi-submersible rely on large amounts of ballast and complex structural designs with active stabilisation systems for stability of the floating offshore wind turbine platform (FOWT). The primary focus of this study is to present a design concept and mooring arrangement for an alternative floating platform solution that places emphasis on the mooring system to achieve stability for a FOWT. The tension leg buoy (TLB) is designed to support future 10MW offshore wind turbine generators. This paper presents the numerical methodology used for a coupled hydro-elastic analysis of the floater and mooring system under combined wind, wave and current effects. A concept TLB design is presented and its platform motion and mooring line tension characteristics are analysed for a three-hour time domain simulation representing operating and survival conditions in the northern North Sea with water depths of 110 metres. The importance of wave drift forces and the other non-linear excitation forces in the concept design stage are evaluated by comparing the motion and tension responses of three different numerical simulation cases with increasing numerical complexity. The preliminary TLB system design demonstrated satisfactory motion response for the operation of a FOWT and survival in a 100-year storm condition. The results show that accounting for second-order effect is vital in terms of having a clear understanding of the full behaviour of the system and the detailed response characteristics in operational and survival conditions. Extreme loads are significantly reduced when accounting for the second-order effects. This can be a key aspect to not overdesign the system and consequently achieve significant cost savings.

scholarly journals Construction and installation engineering for floating wind turbines

2022 ◽  
Vol 355 ◽  
pp. 03068
Author(s):  
A.P. Crowle ◽  
PR Thies
Keyword(s):  
Project Management ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Best Practice ◽  
Green Energy ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Design Engineers ◽  
Floating Offshore Wind Turbines

The construction and installation engineering of floating offshore wind turbines is important to minimize schedules and costs. Floating offshore wind turbine substructures are an expanding sector within renewable power generation, offering an opportunity to deliver green energy, in new areas offshore. The floating nature of the substructures permits wind turbine placement in deep water locations. This paper investigates the construction and installation challenges for the various floating offshore wind types. It is concluded that priority areas for project management and design engineers minimising steel used in semi submersible construction, reducing the floating draft of Spars and for Tension Leg Platforms developing equipment for a safe installation. Specifically tailored design for construction and installation includes expanding the weather window in which these floating substructures can be fabricated, transported to and from offshore site and making mooring and electrical connection operations simpler. The simplification of construction methodology will reduce time spent offshore and minimise risks to installation equipment and personnel. The paper will include the best practice for ease of towing for offshore installation and the possible return to port for maintenance. The construction and installation process for a floating offshore wind turbine varies with substructure type and this will be developed in more detail in the paper. Floating offshore wind structures require an international collaboration of shipyards, ports and construction vessels, though to good project management. It is concluded that return to port for maintenance is possible for semi submersibles and barges whereas for Spars and TLP updated equipment is required to carry out maintenance offshore. In order to facilitate the construction and to minimize costs, the main aspects have to be considered i.e., the required construction vessel types, the distance from fit-out port to site and the weather restrictions.

Numerical Design of a Floating Offshore Wind Turbine Large Scale Model for Control Purposes

2021 ◽  
Author(s):  
Federico Taruffi ◽  
Simone Di Carlo ◽  
Sara Muggiasca ◽  
Alessandro Fontanella
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Large Scale ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Floating Offshore Wind Turbine ◽  
Numerical Design ◽  
Blue Growth

Abstract This paper deals with the numerical design of a floating offshore wind turbine outdoor large-scale prototype based on the DTU 10MW. The objective of this work is to develop a numerical simulation environment for the design of an outdoor scaled prototype. The numerical model is realized coupling the preliminary designed Blue Growth Farm large-scale turbine model with a traditional floater, the OC3 spar buoy. The numerical model is used to evaluate the loads associated with the wind turbine when combined to a floating foundation, with the focus on the coupling between the dynamics of the control system and the one of the floating platform. In addition to this, also the consistency of loads on crucial turbine components is an interesting test bench for the evaluation of the dynamical effects and drives the final design of the physical model.

scholarly journals Structural Modeling and Failure Assessment of Spar-Type Substructure for 5 MW Floating Offshore Wind Turbine under Extreme Conditions in the East Sea

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6571
Author(s):  
Kwangtae Ha ◽  
Jun-Bae Kim ◽  
Youngjae Yu ◽  
Hyoung-Seock Seo
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Offshore Wind ◽  
East Sea ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Offshore Wind Energy ◽  
Floating Offshore Wind Turbine ◽  
Load Analysis

Not only the driving for offshore wind energy capacity of 12 GW by Korea’s Renewable Energy 2030 plan but also the need for the rejuvenation of existing world-class shipbuilders’ infrastructures is drawing much attention to offshore wind energy in Korea, especially to the diverse substructures. Considering the deep-sea environment in the East Sea, this paper presents detailed modeling and analysis of spar-type substructure for a 5 MW floating offshore wind turbine (FOWT). This process uses a fully coupled integrated load analysis, which was carried out using FAST, a widely used integrated load analysis software developed by NREL, coupled with an in-house hydrodynamic code (UOU code). The environmental design loads were calculated from data recorded over three years at the Ulsan Marine buoy point according to the ABS and DNVGL standards. The total 12 maximum cases from DLC 6.1 were selected to evaluate the structural integrity of the spar-type substructure under the three co-directional conditions (45°, 135°, and 315°) of wind and wave. A three-dimensional (3D) structural finite element (FE) model incorporating the wind turbine tower and floating structure bolted joint connection was constructed in FEGate (pre/post-structural analysis module based on MSC NASTRAN for ship and offshore structures). The FEM analysis applied the external loads such as the structural loads due to the inertial acceleration, buoyancy, and gravity, and the environmental loads due to the wind, wave, and current. The three-dimensional FE analysis results from the MSC Nastran software showed that the designed spar-type substructure had enough strength to endure the extreme limitation in the East Sea based on the von Mises criteria. The current process of this study would be applicable to the other substructures such as the submersible type.

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