Load Calculation on Wind Turbines: Validation of Flex5, Alaska/Wind, MSC.Adams and SIMPACK by Means of Field Tests

Zierath, János; Rachholz, Roman; Woernle, Christoph; Müller, Andreas

doi:10.1115/detc2014-34670

Cited by 10 publications

(7 citation statements)

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“…Control elements can either be integrated by external dynamic‐link libraries or direct coupling of Simulink models. Simpack has been successfully applied for the simulation of the dynamic response of wind turbine gearboxes, pitch systems and both fixed bottom and floating offshore wind turbines . The high‐fidelity modeling functionality of Simpack is required to display correctly the non‐linear dynamics of the flexible hub connection.…”

Section: Numerical Methodologymentioning

confidence: 98%

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

Luhmann

Seyedin²,

Cheng

2016

Wind Energy

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In this study, an innovative concept for load reduction on the two-bladed Skywind 3.4 MW prototype is presented. The load reduction system consists of a flexible coupling between the hub mount, carrying the drive train components including the hub assembly, and a nacelle carrier supported by the yaw bearing. This paper intends to assess the impact of introducing a flexible hub connection on the system dynamics and the aero-elastic response to aerodynamic load imbalances. In order to limit the rotational joint motion, a cardanic spring-damper element is introduced between the hub mount and the nacelle carrier flange, which affects the system response and the loads. A parameter variation of the stiffness and damping of the connecting spring-damper element has been performed in the multi-body simulation solver Simpack. A deterministic, vertically sheared wind field is applied to induce a periodic aerodynamic imbalance on the rotor. The aero-structural load reduction mechanisms of the coupled system are thereby identified. It is shown that the fatigue loads on the blades and the turbine support structure are reduced significantly. For a very low structural coupling, however, the corresponding rotational deflections of the hub mount exceed the design limit of operation. The analysis of the interaction between the hub mount motion and the blade aerodynamics in a transient inflow environment indicates a reduction of the angle of attack amplitudes and the corresponding fluctuations of the blade loading. Hence, it can be concluded that load reduction is achieved by a combination of reduced structural coupling and a mitigation of aerodynamic load imbalances.

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Section: Numerical Methodologymentioning

confidence: 98%

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

Luhmann

Seyedin²,

Cheng

2016

Wind Energy

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“…Gözcü and D. R. Verelst: The effects of blade structural model fidelity 5 MW blade (Jonkman et al, 2009) and that a linear beam model underpredicts the blade torsional loads. Zierath et al (2014) compared simulation results using different solvers with measurements of a 2.05 MW prototype wind turbine. The best agreement with measurements was obtained when a multibody dynamic solver was used, since it is able to include nonlinear effects due to large deflections.…”

Section: Introductionmentioning

confidence: 99%

The effects of blade structural model fidelity on wind turbine load analysis and computation time

Gözcü

Verelst

2020

Wind Energ. Sci.

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Abstract. Aero-servo-elastic analyses are required to determine the wind turbine loading for a wide range of load cases as specified in certification standards. The floating reference frame (FRF) formulation can be used to model the structural response of long and flexible wind turbine blades. Increasing the number of bodies in the FRF formulation of the blade increases both the fidelity of the structural model and the size of the problem. However, the turbine load analysis is a coupled aero-servo-elastic analysis, and computation cost not only depends on the size of the structural model, but also depends on the aerodynamic solver and the number of iterations between the solvers. This study presents an investigation of the performance of the different fidelity levels as measured by the computational cost and the turbine response (e.g., blade loads, tip clearance, tower-top accelerations). The analysis is based on aeroelastic simulations for normal operation in turbulent inflow load cases as defined in a design standard. Two 10 MW reference turbines are used. The results show that the turbine response quickly approaches the results of the highest-fidelity model as the number of bodies increases. The increase in computational costs to account for more bodies can almost entirely be compensated for by changing the type of the matrix solver from dense to sparse.

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“…The linear modal space is not used for load calculation and there is no load comparison in the study. There are many studies in the literature on code to code comparisons, where loads were calculated by linear and nonlinear blade models.…”

Section: Introductionmentioning

confidence: 99%

Representation of wind turbine blade responses in power production load cases by linear mode shapes

Gözcü

Stolpe

2020

Wind Energy

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The wind turbine industry is designing large MW size turbines with very long blades, which exhibit large deflections during their operational life. These large deflections decrease the accuracy of linear models such as linear finite element and modal-based models, in which the structure is represented by linear mode shapes. The aim of this study is to investigate the competence of the mode shapes to represent the large blade responses in normal operation load cases. For this purpose, blade deflections are projected onto the linear modal space, swept by mode shape vectors. The projection shows the contribution of each mode and the projection error. The blade deflections are calculated by a nonlinear aero-servo-elastic solver for power production fatigue load cases with normal turbulence. The mode shapes are calculated at the steady-state deflected blade position computed at different wind speeds. Three reference turbine blades are used in the study to evaluate the effects of various blade design parameters such as length, stiffness, mass, and prebend. The results show that although the linear mode shapes can represent the flapwise and edgewise deflections accurately, axial and torsional deflections cannot be captured with good accuracy. The geometric nonlinear effects are more apparent in the latter directions.The results indicate that the blade deflections occur beyond the linear assumptions. KEYWORDSgeometric nonlinearity, structural dynamics, wind energy, wind turbine aeroelasticity, wind turbine loads INTRODUCTIONThe wind turbine design process requires a wide range of different simulations including load and stability analysis and design optimization.Although, some analyses need models with only one uncoupled turbine property such as aerodynamic and structure, others need coupled models which have couplings between the structure, the aerodynamics, and the controller. Coupled turbine analyses generally use low fidelity models because of the high computational cost and difficulties in the coupling process. For example, turbine load analyses are generally performed by the blade element momentum (BEM) 1 method for the aerodynamic part and beam solvers or reduced order models for the structural part. The structural model can be geometrically linear or nonlinear depending on the solver capabilities and available computation resources. The focus of this study is to assess the capabilities of using linear mode shapes in reduced order structural models in stability, aeroelastic, and load analysis of modern turbines.Linear modes constitute a simple and fundamental modeling alternative for most of the linear dynamic problems. Small size, cost effective, and reliable reduced order models 2-6 can be constructed by the mode shapes to calculate the structural response. It is also the key part of the stability analysis. Therefore, reduced order models are also preferred in wind turbine load and stability analysis. 7,8 Although, these models work very well for the structures with small deflections, their accuracy decreases as...

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Load Calculation on Wind Turbines: Validation of Flex5, Alaska/Wind, MSC.Adams and SIMPACK by Means of Field Tests

Cited by 10 publications

References 0 publications

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

The effects of blade structural model fidelity on wind turbine load analysis and computation time

Representation of wind turbine blade responses in power production load cases by linear mode shapes

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