The Mare-Wint research projects will focus around 5 Work Packages linked to the 14 Fellows' research activities. List of Research Projects (Task) and type of fellowship (ESR - early-stage researcher) are presented below.
WP1. Innovative Rotor Blades (Leader: DTU)
Research Project Title
Multi-Scale modelling of manufacturing induced defects in OWT blades
The multi-scale approach to investigate manufacturing induced defects in OWT blades will be carried out and validated within secondments to blade manufacturer SSP. Composite material structures experimental investigation of the various defect types with different load configurations will provide model verification data and knowledge on the critical material parameters governing the response of polymer composite material test specimens. Structural sub-component testing will be focused on non-linear response. New loading and measurement techniques will be investigated in full scale testing at DTU test facilities. By developing a solid understanding of the material processes involved in defect/damage progression, along with the practical tools to investigate structural health in a particular blade, the deterministic criteria will be provided for the quality control requirement during manufacturing, the maintenance effort in operation (carried out in collaboration, through secondments, with Relex), and correct decision towards the end of service life.
CFD investigation of the near-blade 3D flow for a complete OWT configuration
This research aims at capturing physics of wind flow. Complex geometries and unsteady wind flows based on the full CFD analysis will be modelled in order to simulate power and loading characteristics. Investigated models will account for blade rotation, blade installation angle, velocity vector in absolute and related frame of reference, rotational speed which is crucial for determining wind load on the blade. The Wind Multi-Block (WMB) solver developed at University of Liverpool’s CFD lab will be used in this work to investigate the predictive capability of CFD and provide insight in the obtained flow angle measurements. The WMB solver will be validated against available experimental data within the secondment to CENER. Following this step, calculations will be carried out for the complete wind turbine and compared with experimental local flow angles. The complete model and data will be made available to the network to be used in conjunction with other methods for the structural and aerodynamic analysis of WTs. Emphasis will be placed on the exchange of information between fluid and structural simulations, flow control devices and wave load estimates so that a complete simulation of an OWT can be obtained. This task will involve CENER and Axsym. Synergies with Tasks 2.2 of ESR_4 on Multi-Body models are to be pursued within secondments to LMS. Secondment to Axsym to absorb the overall interactions between the involved disciplines. 10% will be devoted to the fluidic flow control mechanisms of IMP-PAN.
WP 2. Drive Train with Gearbox (Leader: LMS)
Simulation and experimental validation of drive train loads for offshore specific conditions
Guaranteeing a robust and reliable OWT drive train design under increasingly demanding conditions both with regard to increasing power output and cost constraints requires expert insights into the dynamic loading of the drive train. This model will be used to investigate the dynamic loading at the drive train interfaces under all relevant representative wind turbine offshore loading conditions. For an OWT wind loading, structural flexibility, drive train behaviour and the generator excitation caused by electricity grid related events should be accurately captured in the defined multibody model. Assessment will be made of the implications of the offshore environment on the dynamic loading of the wind turbine drive train Furthermore, a resonance and excitation analysis is performed on the full wind turbine model to assess the ability of the offshore conditions to excite resonances harmful for the drive train. Secondments of 30% of the duration to Hansen is planned to follow the Industrial PhD scheme and validate MB models against 13 MW full scale gearbox test rig.
Strategy for model updating based on experimental data from drive train test facility
Multibody models can only add value to the design process if simulation results prove to be representative and reliable, which requires sufficient experimental validation. Therefore, the goal of this task is to set up an efficient and feasible measurement plan and campaign for experimental structural load identification of a wind turbine gearbox. To facilitate these measurements in efficient manner cooperation with our industrial partner Hansen Transmissions International is foreseen. Goal of the final task is to close the loop towards simulation and design by doing model updating of the multibody model with the results of the measurement. Focus is on the model update to increase the prediction quality of the drive train loads, drive train modal behaviour to realize a model that accurately represents the drive train dynamics for offshore wind turbines under characteristic operating conditions. Secondment of 30% of the duration to K.U.Leuven is planned to follow the Industrial PhD scheme.
WP 3. Offshore Support Structure (Leader: NTNU)
Dynamic modelling and analysis of a floating wind turbine concept, and comparison with laboratory test data or field measurements
Deep water, floating support systems will be investigated, primarily with turbines based on spar and semi-submersible structures. WP3 research contributes to development of tools for integrated design of wind energy facilities and studies of offshore wind turbine concepts; with due account of the wind and sea environment, hydrodynamic and aerodynamic loads, with due consideration of the structure and foundation or mooring system, energy conversion system and automatic control systems. Time domain as well as frequency domain approaches will be addressed. Numerical model outcomes will be validated against laboratory test data or field measurements at the full scale floating wind turbine test site for relevant concepts. The research will focus on features not yet covered in existing software, especially relating to moored, floating wind turbines concepts. These concepts will be verified through secondments to the MARINTEK and CTC. The novel features will as far as possible be integrated in existing, robust and internationally leading software. Coupled dynamic modelling and analysis, based on both existing software and especially adapted in-house time domain models, will be performed. The task will draw upon new knowledge and numerical sub-models being developed in other tasks of MARE-WINT and other projects. A key outcome of this approach will be the identification of the relevant dimensional parameters influencing the performance and reliability of the generated concepts.
Bottom fixed substructure analysis, model testing and design for harsh environment
The bottom–fixed support structures for offshore wind towers, characterized by the following different configurations and methods of installation, will be studied: gravity structures, monopiles, tripods and jackets.
WP 4. Reliability and Predictive Maintenance (Leader: TWI)
Offshore Wind Turbine condition monitoring based on acoustic emission and long range ultrasonic
The hosted researcher will be working on the development of structural health monitoring technique for the tower and the blade of the wind turbine. This work will be divided into stages: 1) Modelling and theoretical study: Guided wave testing is a method that can characterise the properties of a particular material. There are an infinite number of wave modes, any of which (or a combination thereof) may be best suited for the detection of various defects. The directionality of the composite material for example may be dispersive when elastic energy is initiated at certain angles. Thus, the most helpful way of presenting wave-speed data is in the form of dispersion curves. Such information will indicate which modes are most suited for the identification of particular defects. Therefore this Task will focus upon semi-analytical finite element methods for isotropic (steel towers) and anisotropic (composite blades) materials. This will account for viscoelastic damping and enable the ideal modes to be identified to maximise sensitivity to damage occurring in the composite panel. 2) Transducer array design with aim of design and optimise a suitable transducers array that can be deployed for use on the towers and the blades. This transducers array should be able to detect Acoustic Emission signals and emit Long Range Ultrasonic waves. This will be validated through an experimental plan under secondment to Narec and Shipyard.
Detection of damage in metallic and composite structures for offshore applications
The research will be focused on the development of SHM technique for support structure (isotropic material) and composite blades (anisotropic material) of the OWT. Work will span Numerical methods will comprise Finite Element Method, Spectral Element Method and Time domain Spectral Element Method for simulation of the structures with and without discontinuities (crack, corrosion, delamination, fibres matrix cracking). Experimental techniques investigated will cover Thermal imaging methods and Fiber Bragg Grating sensor technology. Optimal number and location of transducers will be investigated with the criteria of maximise the sensitivity of damage identification for the proposed methods. Digital signal processing techniques will be applied such as FFTs, wavelets and filtering to adequately distinguish signal induced by damage from signal caused from the environmental change (e.g. temperature). Dedicated software will be developed for signal processing and pattern recognition and be validated through an experimental plan under secondment to Fibresensing and Shipyard.
Reducing fatigue loads due to wake effects for offshore wind farm
One of the objectives of MARE-WINT is to reduce fatigue loads experienced by wind turbines. The wind turbines in a wind farm influence each other through the wind field. For this purpose wind field distribution over the entire wind farm will be modelled by means of CFD techniques. Then it will be validated against experimental data from the ECN full scale wind farm as well as the ECN scaled wind farm. Developed dynamic flow model will relate single turbine production and fatigue load to the map of wind speeds. The model will be integrating the wind farm aerodynamics to the dynamics of individual turbines by means of wake meandering and analysis of the wake deficit. Secondment to NUMECA oriented on the CFD model validation is planned.
Risk Assessment of the collision of passing ships with the offshore wind farm
Offshore wind energy production can be disrupted not only due to the failure of the OWT related to wear, fatigue, or overload. Therefore research within WP4 will be looking into current practice of assessment of safety risk and environmental impact. It will develop method to cope with both aspects within one framework. Ideally, the environmental impact assessment will deliver the scenarios for the future development of wildlife in the area of an offshore installation. It will also deliver the baseline data for safety assessments. These data will help to assess the consequences of an accident (e.g., a collision and a resulting spill of hazardous chemicals into the water). The researcher will look into the different safety assessment practices to come up with a suggestion on how this can be either integrated in environmental impact assessment. An important part is the modelling of consequences of accidents for the environment. The investigation will be implemented through following steps 1): Overview about current approaches in assessing the risk of collisions with offshore installations, 2) Overview about consequences models to be used in the assessment of accidental consequences of a collision between ships and offshore installations, 3) Overview about the planning requirements to get permissions for the installation of wind parks in selected EU countries and finally 4) Development, test and validation of a framework for an integrated safety and environmental impact assessment including the assessment of consequences.
Offshore Wind Turbine reliability modelling and analysis
Almost all the ESRs are partially involved in this WP aiming at developing functional and reliability models of the different wind turbine components (blade, drive train, support). The objective is to construct logical models of failure mode growth and propagation based on understanding the failure modes, their mechanisms and the physical magnitudes and variables that are involved in the phenomena. In this sight, the ESR_11 will strongly interact with the other ESRs. Component models will be assembled as “building blocks” in order to develop a complete full OWT reliability model in the Relex Reliability Assessment Model software. These reliability models will contribute to MARE-WINT project objectives which are Design for Reliability and Reliability Centered Maintenance. RCM Process will be used to optimize operation and maintenance in four major steps: a) Planning, b) Analysis, c) Implementation and d) Sustain the Analysis.
WP 5. Fluid-Structure Interaction (Leader: NUMECA)
RANS simulation applications for hydro-elastic floating substructure predictions
The objectives of the coupled hydro-elastic modelling of OWT is to explore the technologies needed for development of a modelling method capable to predict realistic physical behaviour of complex systems where the interactions of fluid and structural responses are significant. The coupling will be implemented through advanced mesh deformation technique capturing the free surface in time without the need of re-meshing, thus saving resources. The developed method will be applied to analyze the behaviour of wind turbine coupled with support structures, coming from WP3, and evaluation of accuracy of obtained results.
Twist-coupled aero-elastic design for passive loads reduction on a full scale blade
Research work will focus on methods to tailor the structural couplings in the blade design, coming from WP1, in order to obtain passive load reduction without compromising the efficiency of the wind turbine. Possible ways to build in couplings in wind turbine blades will be analyzed. The benefit of build in couplings in terms of passive load reduction will be predicted and optimization tools will be used in order to obtain optimal solutions. Benefits and drawbacks with respect to aero-elastic behaviour and structural design will be analysed. Possibilities of combining passive load reduction with active systems will be analyzed. The ultimate objective is to make a contribution to future blades that can be produced more cost effectively, are lighter, more reliable and have better aerodynamic behaviour. It will be explored how the approach can be extended to sectional blades within secondments to SSP.
Active flow control for improving aerodynamic performance and noise reduction
The numerical and experimental investigations for flow conditions, coming from WP1, with active control devices will be the next research topic within WP5. Objective is to develop open and closed-loop active flow control strategies based on unsteady suction and/or blowing to: delay flow separation and stall in real time; and optimize the overall efficiency and minimize associated noise. Different flow control methods will be investigated in basic configurations, designed in order to obtain maximum aerodynamic performance of the rotor for selected flow cases. Obtained results will be the main criteria for wind tunnel tests blade section flow measurements and numerical simulations. Numerical models will be incorporated into the multi-physics co-simulation platform (secondment to LIV). The results will be used in a multitude of ways within the project. The complex physics of the flow control devices must be simulated within the overall aerodynamic research of ESR_2 and their effect on the overall performance of the blade should be quantified. The near field simulation should be detailed enough to capture the fluidic mechanism of the devices but also to allow for at least the near-field noise to be exported to acoustic methods. This is a challenging task given the difficulties of CFD with resolving shallow separation and accurately representing the details of the boundary layer structures, turbulence and noise. The experiments done within secondment to CENER will therefore be unique to the aerodynamics modelling community and not only will enhance our understanding of OWT fluid mechanics but also push the current state of the art forward by providing databases and insights that will be exploited within the consortium.