Comparison of Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine and Numerical Simulations

2017 ◽  
Author(s):  
Madjid Karimirad ◽  
Erin E. Bachynski ◽  
Petter Andreas Berthelsen ◽  
Harald Ormberg
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Hybrid Model ◽  
Low Frequency ◽  
Ocean Basin ◽  
Model Testing ◽  
Second Order ◽  
Experimental Results ◽  
Scaled Model ◽  
Approximate Methods

In this paper, integrated analyses performed in SIMA are compared against experimental results obtained using real-time hybrid model testing (ReaTHM®) carried out in the ocean basin facilities of MARINTEK in October 2015. The experimental data is from a 1:30 scaled model of a semi-submersible wind turbine. Coupled aero-hydro-servo-elastic simulations are performed in MARINTEK’s SIMA software. The present work extends previous results from Berthelsen et al. [1] by including a blade element/momentum (BEM) model for the rotor forces in SIMA and comparing the coupled responses of the system to the experimental results. The previously presented hydrodynamic model is also further developed, and the importance of second order loads (and applicability of approximate methods for their calculations) is examined. Low-frequency hydrodynamic excitation and damping are seen to be important, but these loads include a combination of viscous and potential forces. For the selected concept, the second order potential flow forces have limited effects on the responses.

scholarly journals Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine: Part II — Experimental Results

2016 ◽  
Author(s):  
Erin E. Bachynski ◽  
Maxime Thys ◽  
Thomas Sauder ◽  
Valentin Chabaud ◽  
Lars Ove Sæther
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Hybrid Model ◽  
Low Frequency ◽  
Physical Structure ◽  
Ocean Basin ◽  
Test Method ◽  
Experimental Results ◽  
Irregular Waves ◽  
Aerodynamic Loads

Real-Time Hybrid Model (ReaTHM) tests of a braceless semi-submersible wind turbine were carried out at MARINTEK’s Ocean Basin in 2015. The tests sought to evaluate the performance of the floating wind turbine (FWT) structure in environmental conditions representative of the Northern North Sea. In order to do so, the tests employed a new hybrid testing method, wherein simulated aerodynamic loads were applied to the physical structure in the laboratory. The test method was found to work well, and is documented in [1]. The present work describes some of the experimental results. The test results showed a high level of repeatability, and permitted accurate investigation of the coupled responses of a FWT, including unique conditions such as blade pitch faults. For example, the influence of the wind turbine controller can be seen in decay tests in pitch and surge. In regular waves, aerodynamic loads due to constant wind had little influence on the structure motions (except for the mean offsets). Tests in irregular waves with and without turbulent wind are compared directly, and the influence of the wave-frequency motions on the aerodynamic damping of wind-induced low-frequency motions can be observed.

scholarly journals Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine: Part I — The Hybrid Approach

2016 ◽  
Author(s):  
Thomas Sauder ◽  
Valentin Chabaud ◽  
Maxime Thys ◽  
Erin E. Bachynski ◽  
Lars Ove Sæther
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Physical Model ◽  
Hybrid Model ◽  
Hybrid Approach ◽  
Physical Modelling ◽  
Short Review ◽  
Ocean Basin ◽  
Model Testing ◽  
Aerodynamic Load

This article presents a method for performing Real-Time Hybrid Model testing (ReaTHM testing) of a floating wind turbine (FWT). The advantage of this method compared to the physical modelling of the wind in an ocean basin, is that it solves the Froude-Reynolds scaling conflict, which is a key issue in FWT testing. ReaTHM testing allows for more accurate testing also in transient conditions, or degraded conditions, which are not feasible yet with physical wind. The originality of the presented method lies in the fact that all aerodynamic load components of importance for the structure were identified and applied on the physical model, while in previous similar projects, only the aerodynamic thrust force was applied on the physical model. The way of applying the loads is also new. The article starts with a short review (mostly references) of ReaTHM testing when applied to other fields than marine technology. It then describes the design of the hybrid setup, its qualification, and discusses possible error sources and their quantification. The second part of the article [1] focuses on the performance of a braceless semi-submersible FWT, tested with the developed method. The third part [2] describes how the experimental data was used to calibrate a numerical model of the FWT.

Hybrid Model Tests for Floating Offshore Wind Turbines

2019 ◽  
Author(s):  
Maxime Thys ◽  
Alessandro Fontanella ◽  
Federico Taruffi ◽  
Marco Belloli ◽  
Petter Andreas Berthelsen
Keyword(s):  
Wind Tunnel ◽  
Real Time ◽  
Hybrid Model ◽  
Wind Turbines ◽  
Ocean Basin ◽  
Model Testing ◽  
Model Tests ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Abstract Model testing of offshore structures has been standard practice over the years and is often recommended in guidelines and required in certification rules. The standard objectives for model testing are final concept verification, where it is recommended to model the system as closely as possible, and numerical code calibration. Model testing of floating offshore wind turbines is complex due to the response depending on the aero-hydro-servo-elastic system, but also due to difficulties to perform model tests in a hydrodynamic facility with correctly scaled hydrodynamic, aerodynamic and inertial loads. The main limitations are due to the Froude-Reynolds scaling incompatibility, and the wind generation. An approach to solve these issues is by use of hybrid testing where the system is divided in a numerical and a physical substructure, interacting in real-time with each other. Depending on the objectives of the model tests, parts of a physical model of a FOWT can then be placed in a wind tunnel or an ocean basin, where the rest of the system is simulated. In the EU H2020 LIFES50+ project, hybrid model tests were performed in the wind tunnel at Politecnico di Milano, as well as in the ocean basin at SINTEF Ocean. The model tests in the wind tunnel were performed with a physical wind turbine positioned on top of a 6DOF position-controlled actuator, while the hydrodynamic loads and the motions of the support structure were simulated in real-time. For the tests in the ocean basin, a physical floater with tower subject to waves and current was used, while the simulated rotor loads were applied on the model by use of a force actuation system. The tests in both facilities are compared and recommendations on how to combine testing methodologies in an optimal way are discussed.

Real-Time Hybrid Model Testing of a Semi-Submersible 10MW Floating Wind Turbine and Advances in the Test Method

2018 ◽  
Author(s):  
Maxime Thys ◽  
Valentin Chabaud ◽  
Thomas Sauder ◽  
Lene Eliassen ◽  
Lars O. Sæther ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Physical Model ◽  
Hybrid Model ◽  
Parallel Robot ◽  
Ocean Basin ◽  
Model Tests ◽  
Test Method ◽  
Load Application ◽  
Floating Wind Turbine

This article presents the Real-Time Hybrid Model (ReaTHM®) tests that were performed on a 10-MW semi-submersible floating wind turbine in the Ocean Basin at SINTEF Ocean in March 2018. The ReaTHM test method was used for the model tests to circumvent the limitations encountered when performing model tests with wind and waves. The physical model was subject to physical waves, while the rotor and tower loads were simulated in real-time and applied on the model by use of a cable-driven parallel robot. Recent advances in the ReaTHM test method allowed for extended testing possibilities and load application up to the 3p frequency and the first tower bending frequency.

Real-Time Hybrid Model Testing of a Top Tensioned Riser: A Numerical Case Study on Interface Time-Delays and Truncation Ratio

2017 ◽  
Author(s):  
Thomas Sauder ◽  
Asgeir J. Sørensen ◽  
Kjell Larsen
Keyword(s):  
Water Column ◽  
Real Time ◽  
Hybrid Model ◽  
Ocean Basin ◽  
Model Testing ◽  
Sensors And Actuators ◽  
Test Setup ◽  
System A ◽  
Actuation System

This paper investigates the applicability of real-time hybrid model testing (ReaTHM testing) to the study of offshore systems in deep water. The focus is in particular on slender marine structures connecting floating structures to the seabed, and on how they could be truncated so that a model test setup at a reasonable scale could fit existing hydrodynamic laboratory infrastructures. In this context, ReaTHM testing consists in “substructuring” the slender structures in two parts. At the lower part of the water column, the first substructure is numerical, simulated using a nonlinear finite element method. On the upper part of the water column, the other substructure is physically modelled in an ocean basin. Both substructures interact in real-time through a set of sensors and actuators. This paper addresses through a case study the important issue of accuracy of ReaTHM testing, that is how the behavior of the substructured system varies from that of the emulated system. A top-tensioned riser in 1200m water depth is considered, with two truncation locations: 240m and 600m below the free surface. It is assumed that an artefact is introduced by the ReaTHM test setup, namely a time delay induced by e.g. the numerical calculations, or the actuation system. It is first shown how this artefact influences the accuracy of the setup, and then how the truncation ratio influences the tolerance of the ReaTHM test setup to such an artefact.

scholarly journals Model tests of a 10 MW semi-submersible floating wind turbine under waves and wind using hybrid method to integrate the rotor thrust and moments

2021 ◽  
Author(s):  
Felipe Vittori ◽  
José Azcona ◽  
Irene Eguinoa ◽  
Oscar Pires ◽  
Alberto Rodríguez ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Natural Frequency ◽  
Hybrid Method ◽  
Deep Ocean ◽  
Ocean Basin ◽  
Experimental Results ◽  
Floating Platform ◽  
Scaled Model ◽  
Floating Wind Turbine ◽  
Tank Test

Abstract. This paper describes the results of a wave tank test campaign of a 1/49 scaled SATH 10MW INNWIND floating platform. The Software-in-the-Loop (SiL) hybrid method was used to include the wind turbine thrust and the in-plane rotor moments My – Mz. Experimental results are compared with a numerical model developed in OpenFAST of the floating wind turbine. The tank test campaign was carried out in the scaled model tested at the Deep Ocean Basin from the Lir National Ocean TF at Cork, Ireland. This floating substructure design was adapted by Saitec to support the 10MW INNWIND wind turbine within the ARCWIND project with the aim of withstanding the environmental conditions of the European Atlantic Area region. CENER provided the wind turbine controller specially designed for the SATH 10MW configuration. A description of the experimental set up, force actuator configuration and the numeric aerodynamic parameters are provided in this work. The most relevant experimental results under wind and wave loading are showed in time series and frequency domain. The influence of the submerged geometry variations in the pitch natural frequency is discussed. The paper shows the simulation of a case with rated wind speed, where the tilted geometry for the computation of the hydrostatic and hydrodynamic properties of the submerged substructure is considered. This case provides a better agreement of the pitch natural frequency with the experiments, than a equivalent simulation using the undisplaced geometry mesh for the computation of the hydrodynamic and hydrostatic properties.

Real-Time Hybrid Model Tests of a Braceless Semi-Submersible Wind Turbine: Part III — Calibration of a Numerical Model

2016 ◽  
Author(s):  
Petter Andreas Berthelsen ◽  
Erin E. Bachynski ◽  
Madjid Karimirad ◽  
Maxime Thys
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Simulation Model ◽  
Wind Turbine ◽  
Real Time ◽  
Hybrid Model ◽  
Test Data ◽  
Viscous Drag ◽  
Drag Coefficients ◽  
Aerodynamic Loads

In this paper, a numerical model of a braceless semi-submersible floating wind turbine (FWT) is calibrated against model test data. Experimental data from a 1:30 scaled model tested at MARINTEK’s Ocean Basin in 2015 using real-time hybrid model testing (ReaTHM) is used for the calibration of the time-domain simulation model. In these tests, aerodynamic loads were simulated in real-time and applied to the physical model. The simulation model is based on the as-built model at full scale. The hull and turbine are considered as rigid, while bar elements are used to model the mooring system in a coupled finite element approach. Frequency-dependent added mass, radiation damping, and excitation forces/moments are evaluated using a panel method based on potential theory. Distributed viscous forces on the hull and mooring lines are added to the numerical model applying Morison’s equation. The viscous drag coefficients in Morison’s equation are calibrated against selected test data, including decay tests in calm water and test with irregular waves. Simulations show that the drag coefficients change when waves are present. Aerodynamic loads are included as time varying loads applied directly at the hub based on the actual physical loads from the experiment. This way, uncertainties related to the aerodynamic loads in the calibrations are removed. The calibrated numerical model shows good agreement with experimental data.

scholarly journals Method for Real-Time Hybrid Model Testing of ocean structures: Case study on horizontal mooring systems

2019 ◽  
Vol 172 ◽  
pp. 46-58 ◽  
Author(s):  
S.A. Vilsen ◽  
T. Sauder ◽  
A.J. Sørensen ◽  
M. Føre
Keyword(s):  
Real Time ◽  
Hybrid Model ◽  
Model Testing
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