scholarly journals Seakeeping Tests of a FOWT in Wind and Waves: An Analysis of Dynamic Coupling Effects and Their Impact on the Predictions of Pitch Motion Response

2021 ◽  
Vol 9 (2) ◽  
pp. 179
Author(s):  
Giovanni Amaral ◽  
Pedro Mello ◽  
Lucas do Carmo ◽  
Izabela Alberto ◽  
Edgard Malta ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Dynamic Coupling ◽  
Coupling Effects ◽  
Mooring Lines ◽  
Scaled Model ◽  
Wave Basin ◽  
Domain Models ◽  
Catenary System

The present work highlights some of the dynamic couplings observed in a series of tests performed in a wave basin with a scaled-model of a Floating Offshore Wind Turbine (FOWT) with semi-submersible substructure. The model was moored by means of a conventional chain catenary system and an actively controlled fan was used for emulating the thrust loads during the tests. A set of wave tests was performed for concomitant effects of not aligned wave and wind. The experimental measurements illustrate the main coupling effects involved and how they affect the FOWT motions in waves, especially when the floater presents a non-negligible tilt angle. In addition, a frequency domain numerical analysis was performed in order to evaluate its ability to capture these effects properly. The influence of different modes of fan response, floater trim angles (changeable with ballast compensation) and variations in the mooring stiffness with the offsets were investigated in the analysis. Results attest that significant changes in the FOWT responses may indeed arise from coupling effects, thus indicating that caution must be taken when simplifying the hydrodynamic frequency-domain models often used as a basis for the simulation of FOWTs in waves and in optimization procedures for the design of the floater and mooring lines.

scholarly journals Seakeeping Tests of a Fowt in Wind and Waves: An Analysis of Dynamic Coupling Effects and Their Impact on the Predictions of Pitch Motion Response

2021 ◽  
Author(s):  
Giovanni Aiosa do Amaral ◽  
Pedro Mello ◽  
Lucas Henrique Souza Carmo ◽  
Izabela Franzão Alberto ◽  
Edgard Borges Malta ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Irregular Waves ◽  
Dynamic Coupling ◽  
Coupling Effects ◽  
Mooring Lines ◽  
Scaled Model ◽  
Wave Basin ◽  
Wind Velocities ◽  
Domain Models ◽  
Made In

The present work highlights some of the dynamic couplings observed in a series of tests performed in a wave basin with a scaled-model of a FOWT with semi-submersible substructure. The model was moored by means of a conventional chain catenary system and an actively controlled fan was used for emulating the thrust loads during the tests. A set of wave tests comprising regular and irregular waves was done for different wave angles and wind velocities. The experimental records illustrate the main coupling effects involved and how they affect the FOWT motions in waves, especially when the floater presents a non-negligible tilt angle.. In addition, an analysis of the frequency-domain dynamic model was made in order to evaluate its ability to capture these effects properly. The influence of different modes of fan response, floater trim angles (changeable with ballast compensation) and variations of the mooring stiffness with the offsets were investigated in the analysis. Results attest that significant changes in the FOWT responses may indeed arise from coupling effects, thus indicating that caution must be taken when simplifying the hydrodynamic frequency-domain models often used as a basis for the simulation of FOWTs in waves and in in optimization procedures for the design of the floater and mooring lines.

scholarly journals Study on Array Floating Platform for Wind Energy and Marine Space Optimization

2021 ◽  
Vol 13 (24) ◽  
pp. 14014
Author(s):  
Yi-Hung Chen ◽  
Ray-Yeng Yang
Keyword(s):  
Numerical Simulation ◽  
Wind Turbines ◽  
Spatial Configuration ◽  
Water Area ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Offshore Water ◽  
Mooring Lines ◽  
Scaled Model ◽  
Wave Basin

The concept of multiline anchor, whose application is mainly considered in water depths beyond 100 m and analyzed only by numerical simulation, has been discussed for half a decade, yet previous studies have not conducted the wave basin experiment. Thus, this paper set this concept firstly with a shallow water mooring system designed for a Taiwan offshore water area, where the suitable water depth for floating offshore wind turbine is located from 50 to 100 m, and then conducted a 1:144 scaled model wave basin experiment to validate the results from numerical simulation. In this paper, the numerical model simulated and analyzed three identical DeepCwind OC4 semi-submersible platforms equipped with NREL 5MW wind turbines in OrcaFlex and the experiment carried out by using three 1:144 scaled semi-submersible platforms with equivalent disks which simulated different operations of wind thrusts. To consider the possible influence of the wake effect, the minimum turbines spacing was set at 750 m in a full scaled model and the length of mooring lines was redesigned according to the catenary theory. This paper utilized OrcaWave to calculate hydrodynamic parameters and input it into OrcaFlex to simulate the line tension and the three degrees of freedom (surge, heave, and pitch) of the platforms under regular and irregular wave tests, and coordinate with scaled model tests carried out in Tainan Hydraulics Laboratory (THL). In addition to the reduction in the number of anchors, the concept of multiline anchor was also discussed in this study for the spatial configuration of offshore wind farms. It shows that the wind farm composed of three floating wind turbines can reduce the ocean space by roughly 24% compared to that with a single-line anchor. According to the comparison of numerical and experimental results, this study finally optimized the mooring lines by changing the diameter to increase the stability and the threshold of Minimum Breaking Load (MBL) and proposed a multiline anchor configuration for shallow offshore water area in Taiwan based on the results obtained.

scholarly journals Hydrodynamic Response of the Deep Turbine Installation-Floating Concept

2019 ◽  
Author(s):  
Jordi Serret ◽  
Tim Stratford ◽  
Philipp R. Thies ◽  
Vengatesan Venugopal ◽  
Tahsin Tezdogan
Keyword(s):  
Numerical Simulations ◽  
Numerical Study ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Mooring Lines ◽  
Scaled Model ◽  
Irregular Wave ◽  
Floating System ◽  
Turbine Installation

Abstract Floating offshore wind turbine (FOWT) installations are progressing from the R&D stage to commercial installation projects. The prospective sites are situated in increasingly deeper water and further away from the shore. This paper presents the Deep Turbine Installation-Floating (DTI-F) concept, an innovative hybrid spar buoy-based FOWT capable of being able to raise and lower the tower and nacelle, which simplifies construction, installation, maintenance and decommissioning. The study is focused on the hydrodynamics of the moored floating system, and it is based on experimental and numerical modelling work. A 1:45 Froude scaled model of the DTI-F wind concept was tested using three different mooring configurations: i) three mooring lines, ii) four mooring lines, and iii) three mooring lines with a delta connection. Free decay and stiffness decay tests were carried out together with regular and irregular wave tests. The numerical study comprises diffraction (ANSYS AQWA) and time-domain modelling (OrcaFlex). The experimental hydrostatic and hydrodynamic results are compared with the numerical simulations based on the as-built scale model. Considering the natural frequencies results obtained for the three mooring configurations, the three lines configuration without delta connection was selected as the most suitable design. The obtained results for the three mooring lines configuration show good agreement between the experiment and numerical simulations. The presented analysis of the design concept indicates a high degree of technical feasibility.

scholarly journals Unsupervised Damage Detection for Offshore Jacket Wind Turbine Foundations Based on an Autoencoder Neural Network

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3333
Author(s):  
Maria del Cisne Feijóo ◽  
Yovana Zambrano ◽  
Yolanda Vidal ◽  
Christian Tutivén
Keyword(s):  
Neural Network ◽  
Wind Turbine ◽  
Environmental Conditions ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Small Subset ◽  
Scaled Model ◽  
Vibration Data ◽  
Large Water

Structural health monitoring for offshore wind turbine foundations is paramount to the further development of offshore fixed wind farms. At present time there are a limited number of foundation designs, the jacket type being the preferred one in large water depths. In this work, a jacket-type foundation damage diagnosis strategy is stated. Normally, most or all the available data are of regular operation, thus methods that focus on the data leading to failures end up using only a small subset of the available data. Furthermore, when there is no historical precedent of a type of fault, those methods cannot be used. In addition, offshore wind turbines work under a wide variety of environmental conditions and regions of operation involving unknown input excitation given by the wind and waves. Taking into account the aforementioned difficulties, the stated strategy in this work is based on an autoencoder neural network model and its contribution is two-fold: (i) the proposed strategy is based only on healthy data, and (ii) it works under different operating and environmental conditions based only on the output vibration data gathered by accelerometer sensors. The proposed strategy has been tested through experimental laboratory tests on a scaled model.

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.

Study on the Dynamic Response for Floating Foundation of Offshore Wind Turbine

2011 ◽  
Author(s):  
Yougang Tang ◽  
Jun Hu ◽  
Liqin Liu
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Load ◽  
Mooring Lines ◽  
Floating Foundation ◽  
Wind Turbine System ◽  
Sea Area

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5–50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. According to the basic data of a 600kW wind turbine with a horizontal shaft, the tower, semi-submersible foundation and mooring system are designed in the 60-meter-deep sea area. Precise finite element models of the floating wind turbine system are established, including mooring lines, floating foundation, tower and wind turbine. Dynamic responses for the floating foundation of offshore wind turbine are investigated under wave load in frequency domain.

scholarly journals Proposal and Performance Study of a Novel Mooring System with Six Mooring Lines for Spar-Type Offshore Wind Turbines

2021 ◽  
Vol 11 (24) ◽  
pp. 11665
Author(s):  
Shi Liu ◽  
Yi Yang ◽  
Chao Wang ◽  
Yuangang Tu
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Included Angle ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Spar-type floating offshore wind turbines commonly vibrate excessively when under the coupling impact of wind and wave. The wind turbine vibration can be controlled by developing its mooring system. Thus, this study proposes a novel mooring system for the spar-type floating offshore wind turbine. The proposed mooring system has six mooring lines, which are divided into three groups, with two mooring lines in the same group being connected to the same fairlead. Subsequently, the effects of the included angle between the two mooring lines on the mooring-system’s performance are investigated. Then, these six mooring lines are connected to six independent fairleads for comparison. FAST is utilized to calculate wind turbine dynamic response. Wind turbine surge, pitch, and yaw movements are presented and analyzed in time and frequency domains to quantitatively evaluate the performances of the proposed mooring systems. Compared with the mooring system with six fairleads, the mooring system with three fairleads performed better. When the included angle was 40°, surge, pitch, and yaw movement amplitudes of the wind turbine reduced by 39.51%, 6.8%, and 12.34%, respectively, when under regular waves; they reduced by 56.08%, 25.00%, and 47.5%, respectively, when under irregular waves. Thus, the mooring system with three fairleads and 40° included angle is recommended.

Global Responses and Loads Analysis of a 750-kW Semi-Submersible Floating Offshore Wind Turbine Under Extreme Environmental Conditions

2019 ◽  
Author(s):  
Thanh Dam Pham ◽  
Junbae Kim ◽  
Byoungcheon Seo ◽  
Rupesh Kumar ◽  
Youngjae Yu ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Environmental Conditions ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
East Sea ◽  
Offshore Wind Turbine ◽  
Test Model ◽  
Scaled Model ◽  
Floating Offshore Wind Turbine ◽  
Extreme Loads

Abstract A pilot floating offshore wind turbine project of Korea was proposed for installing in the East Sea of Korea. The prototype is a semisubmersible platform supporting a 750-kW wind turbine. A scaled model was tested in the basin tank of the University of Ulsan at scale ratio 1:40. The 750-kW floating offshore wind turbine was modeled by using the NREL-FAST code. Numerical results were validated by comparing with those of the test model. This paper analyzes dynamic responses and loads of the wind turbine system under extreme environmental conditions. Extreme environmental conditions based on metocean data of East Sea Korea. Extreme responses and extreme loads are important data for designing the structure of the 750 kW semi-submersible floating offshore wind turbine.

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