The Experts below are selected from a list of 9930 Experts worldwide ranked by ideXlab platform
Kim Branner - One of the best experts on this subject based on the ideXlab platform.
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the effect of delaminations on local buckling in wind turbine Blades
Renewable Energy, 2016Co-Authors: Philipp Ulrich Haselbach, Robert Bitsche, Kim BrannerAbstract:In this article the effect of delaminations on the load carrying capacity of a large wind turbine Blade is studied numerically. For this purpose an 8.65 m long Blade Section with different initial delaminations in the main spar was subjected to a flapwise dominated bending moment. The model was setup in Abaqus and cohesive elements were chosen for modelling delamination growth.
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the effect of delaminations on local buckling in wind turbine Blades
Renewable Energy, 2016Co-Authors: Philipp Ulrich Haselbach, Robert Bitsche, Kim BrannerAbstract:Abstract In this article the effect of delaminations on the load carrying capacity of a large wind turbine Blade is studied numerically. For this purpose an 8.65 m long Blade Section with different initial delaminations in the main spar was subjected to a flapwise dominated bending moment. The model was setup in Abaqus and cohesive elements were chosen for modelling delamination growth. For initial delaminations with a width of 30–50% of the cap width the study showed that delamination close to the surface started to grow in load ranges of normal operation conditions and led to local buckling modes. The local buckling caused high strains and stresses in the surrounding of the delamination, which exceeded the material design properties and therefore should be considered as dangerous. Delaminations placed near the mid-surface of the cap did not have a significant effect on the Blade response under normal operation conditions. In the simulations the static load exceeded the design load by more than 40% before delamination growth or cap buckling occurred. It could be concluded that delamination induced near-surface buckling modes have to be considered critical due to an onset of local sublaminate buckling below the design load level.
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updating finite element model of a wind turbine Blade Section using experimental modal analysis results
Shock and Vibration, 2014Co-Authors: Marcin Luczak, Kim Branner, Simone Manzato, Bart Peeters, Peter Berring, Maciej KahsinAbstract:This paper presents selected results and aspects of the multidisciplinary and interdisciplinary research oriented for the experimental and numerical study of the structural dynamics of a bend-twist coupled full scale Section of a wind turbine Blade structure. The main goal of the conducted research is to validate finite element model of the modified wind turbine Blade Section mounted in the flexible support structure accordingly to the experimental results. Bend-twist coupling was implemented by adding angled unidirectional layers on the suction and pressure side of the Blade. Dynamic test and simulations were performed on a Section of a full scale wind turbine Blade provided by Vestas Wind Systems A/S. The numerical results are compared to the experimental measurements and the discrepancies are assessed by natural frequency difference and modal assurance criterion. Based on sensitivity analysis, set of model parameters was selected for the model updating process. Design of experiment and response surface method was implemented to find values of model parameters yielding results closest to the experimental. The updated finite element model is producing results more consistent with the measurement outcomes.
Epeli Nabolaniwaqa - One of the best experts on this subject based on the ideXlab platform.
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performance studies on a wind turbine Blade Section for low wind speeds with a gurney flap
Journal of Energy Resources Technology-transactions of The Asme, 2019Co-Authors: Rafiuddin M Ahmed, Epeli NabolaniwaqaAbstract:The flow characteristics and the lift and drag behavior of a thick trailing-edged airfoil that was provided with fixed trailing edge flaps (Gurney flaps) of 1% to 5% height right at the back of the airfoil were studied both experimentally and numerically at different low Reynolds numbers (Re) and angles of attack for possible applications in wind turbines suitable for the wind speeds of 4-6 m/s. The flap considerably improves the suction on the upper surface of the airfoil resulting in a higher lift coefficient. The drag coefficient also increased; however, the increase was less compared to the increase in the lift coefficient, resulting in a higher lift-to-drag ratio in the angles of attack of interest. The results show that trailing-edge flaps can improve the performance of Blades designed for low wind speeds and can directly be applied to small wind turbines that are increasingly being used in remote places or in smaller countries.
Yawei Zhu - One of the best experts on this subject based on the ideXlab platform.
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effect of morphed trailing edge flap on aerodynamic load control for a wind turbine Blade Section
Renewable Energy, 2020Co-Authors: Chen Zhuang, Gang Yang, Yawei ZhuAbstract:Abstract Application of Morphed Trailing-Edge Flap (MTEF) can significantly reduce the excessive loads that cause damage of Blades and surrounding components in wind turbine. The present paper investigates the effect of MTEF on the aerodynamic load control of a large-scale wind turbine Blade. Three design parameters that control MTEF kinematics, such as deflection length, amplitude and phase shift, are analyzed in detail by a validated Computational Fluid Dynamic (CFD) model, in which a specially-designed mesh update method is adopted. Results show that, compared with fully rigid airfoil, the morphed airfoil exhibits an excellent load control capability owing to the appropriate change of aft effective camber as deflection motion of MTEF, which significantly alters the pressure distribution and air flow. Furthermore, the performances are linearly improved with increasing MTEF deflection length, wherein every 0.1c increase in length results in the percentage variation of CL, min (+45%), CL, max (−3%), CD, max (−5%) and CL/CD (+30%). Whereas the improved performance due to the increase of deflection amplitude shows a reducing trend, and an oversize deflection amplitude (greater than βamp = 10°) leads to the depravation of aerodynamic efficiency. Moreover, the analysis of deflection phase shift suggests that a slight phase–lag is beneficial to stabilize the aerodynamic load exerted on wind turbine Blade. Especially, the lift coefficient fluctuation (CL, max−CL, min) for the phase-lag case of φ = 1/8π has reduced by about 50% while the cycle-averaged lift coefficient has increased by 16.67% as compared to the fully rigid airfoil. The results of this paper will help guide future development and application of MTEF in practice.
Foulds Deacon - One of the best experts on this subject based on the ideXlab platform.
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Validation of Breathing Modes in Wind Turbine Blade Finite Element Models
2021Co-Authors: Foulds DeaconAbstract:Wind energy is a growing industry, and in an effort to reduce costs and increase turbine efficiency, rotor Blades are becoming increasingly large in size. To facilitate this effort, the SmartBlades2 research project has designed, built, and tested a set of prototype research Blades. As part of the SmartBlades2 project, high sensor density modal testing has been conducted on the research Blades. The analysis of the modal tests showed good agreement of the global vibration modes with the finite element model predictions. However, the test analysis also identified low frequency vibration modes, referred to as breathing modes, which were not predicted by the finite element models. These vibration modes were found on all of the Blades and are characterised by out-of-plane trailing edge panel motion. The objective of this thesis is to identify and predict the aforementioned breathing modes using finite element analysis. To achieve this, three model characteristics are analysed to determine their influence on the breathing mode prediction, namely, model topology, shell element configuration, and material properties. To characterise the affect of model topology, a cut Section from the SmartBlades2 prototype Blade is modelled with shell elements and continuum element glue joints. To validate the Blade Section model, a modal test is conducted which identifies breathing modes analogous to the full Blade. Various topology features are investigated with the focus on the shell glue joints and spar web joints of the Blade Section. The analysis shows that while these changes significantly effect the mode shapes and frequencies, none of them predict the experimentally identified breathing modes. To investigate the source of this discrepancy, the modal behaviour of a sample plate structure with the same materials is used to remove the variability of topology. The effects of shell element size and configuration are analysed with mutual comparisons. The analysis shows that higher fidelity element configurations offer no advantage over linear shell elements for prediction of modal behaviour, while the element size shows higher sensitivity. Furthermore, the effects of material properties are examined using the sample plate, subject to modal and flexural tests. It is found that the specified properties are stiffer than measured, and new predictions of the properties are made which better fit the plates experimental results. Finally, the topology, element, and material investigations are then applied to an improved finite element model of the complete Blade and correlated with the experimental modal tests. It is found that the improved Blade model has closer correlation with the experimental modal tests for global modes, however is unable to predict the identified breathing modes for the Blade. It is hypothesised that cause of this may relate to the connection of the spar web with the glue flanges
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Validation of Breathing Modes in Wind Turbine Blade Finite Element Models
2021Co-Authors: Foulds DeaconAbstract:Wind energy is a growing industry, and in an effort to reduce costs and increase turbine efficiency, rotor Blades are becoming increasingly large in size. To facilitate this effort, the SmartBlades2 research project has designed, built, and tested a set of prototype research Blades. As part of the SmartBlades2 project, high sensor density modal testing has been conducted on the research Blades. The analysis of the modal tests showed good agreement of the global vibration modes with the finite element model predictions. However, the test analysis also identified low frequency vibration modes, referred to as breathing modes, which were not predicted by the finite element models. These vibration modes were found on all of the Blades and are characterised by out-of-plane trailing edge panel motion. The objective of this thesis is to identify and predict the aforementioned breathing modes using finite element analysis. To achieve this, three model characteristics are analysed to determine their influence on the breathing mode prediction, namely, model topology, shell element configuration, and material properties. To characterise the affect of model topology, a cut Section from the SmartBlades2 prototype Blade is modelled with shell elements and continuum element glue joints. To validate the Blade Section model, a modal test is conducted which identifies breathing modes analogous to the full Blade. Various topology features are investigated with the focus on the shell glue joints and spar web joints of the Blade Section. The analysis shows that while these changes significantly effect the mode shapes and frequencies, none of them predict the experimentally identified breathing modes. To investigate the source of this discrepancy, the modal behaviour of a sample plate structure with the same materials is used to remove the variability of topology. The effects of shell element size and configuration are analysed with mutual comparisons. The analysis shows that higher fidelity element configurations offer no advantage over linear shell elements for prediction of modal behaviour, while the element size shows higher sensitivity. Furthermore, the effects of material properties are examined using the sample plate, subject to modal and flexural tests. It is found that the specified properties are stiffer than measured, and new predictions of the properties are made which better fit the plates experimental results. Finally, the topology, element, and material investigations are then applied to an improved finite element model of the complete Blade and correlated with the experimental modal tests. It is found that the improved Blade model has closer correlation with the experimental modal tests for global modes, however is unable to predict the identified breathing modes for the Blade. It is hypothesised that cause of this may relate to the connection of the spar web with the glue flanges.Aerospace Engineerin
Rafiuddin M Ahmed - One of the best experts on this subject based on the ideXlab platform.
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performance studies on a wind turbine Blade Section for low wind speeds with a gurney flap
Journal of Energy Resources Technology-transactions of The Asme, 2019Co-Authors: Rafiuddin M Ahmed, Epeli NabolaniwaqaAbstract:The flow characteristics and the lift and drag behavior of a thick trailing-edged airfoil that was provided with fixed trailing edge flaps (Gurney flaps) of 1% to 5% height right at the back of the airfoil were studied both experimentally and numerically at different low Reynolds numbers (Re) and angles of attack for possible applications in wind turbines suitable for the wind speeds of 4-6 m/s. The flap considerably improves the suction on the upper surface of the airfoil resulting in a higher lift coefficient. The drag coefficient also increased; however, the increase was less compared to the increase in the lift coefficient, resulting in a higher lift-to-drag ratio in the angles of attack of interest. The results show that trailing-edge flaps can improve the performance of Blades designed for low wind speeds and can directly be applied to small wind turbines that are increasingly being used in remote places or in smaller countries.