Integration of System Level CFD Simulations into the Development Process of Wind Turbine Prototypes

Lutz

Krämer

2022

J. Phys.: Conf. Ser.

A high-fidelity process chain is used to numerically investigate the low-frequency emissions from a generic wind turbine under turbulent inflow conditions. It consists of the Computational Fluid Dynamics (CFD) solver FLOWer, which is coupled to the multi-body simulation software SIMPACK to take unsteady aeroelastic effects into account. A realistic flow field for the complex terrain of Perdigão, Portugal is obtained by including the orography and vegetation in the simulation and using a precursor simulation with E-Wind to generate a site- and situation-specific inflow. The acoustic emissions are calculated with the Fflowcs-Williams-Hawkings (FW-H) acoustic solver ACCO. The simulations show that the tower emits noise caused by the blade-tower interaction (BTI) equally strong in all directions. To the sides of the turbine, this contribution is dominant, regardless of the turbulent inflow. The blades, on the other hand, emit significantly more noise under turbulent inflow, especially in streamwise direction, where they become the dominant source. The main noise mechanism here is the low-frequency part of the inflow turbulence (IT), followed by the BTI. The flow field in Perdigão causes additional large-scale variations in IT noise over time.

Section: Studied Wind Turbine and Sitementioning

confidence: 99%

Impact of turbulent inflow and orography on the low-frequency noise sources of a wind turbine

Lutz

Krämer

2022

J. Phys.: Conf. Ser.

“…This is done by means of calibrated correction factors for each point of operation. 34 Comparing the corrected anemometer signals of the controller in SIMPACK for both velocity and direction with the corresponding graphs from the CFD simulation without WT in Figure A1, some deviations can be seen. The apparent time offset results from the application of a delay element (PT1 element) in the controller to smooth the signal in combination with the reduced flow velocity due to the blockage of the WT.…”

Section: Author Contributionsmentioning

confidence: 99%

“…For this purpose, correction curves calibrated to the I82 are used for speed and direction. 34 Further information on this can be found in Appendix A. In addition, a low-pass filter is applied to smooth the signal.…”

Section: Structural Model In Simpackmentioning

confidence: 99%

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Assessment of low‐frequency aeroacoustic emissions of a wind turbine under rapidly changing wind conditions based on an aero‐servo‐elastic CFD simulation

Maas

Arnold³

et al. 2023

Wind Energy

Self Cite

A meteorologically challenging situation that represents a demanding control task (rotational speed, pitch and yaw) for a wind turbine is presented and its implementation in a simulation is described. A high‐fidelity numerical process chain, consisting of the computational fluid dynamics (CFD) solver FLOWer, the multi‐body system (MBS) software SIMPACK and the Ffowcs Williams‐Hawkings code ACCO, is used. With it, the aerodynamic, servoelastic and aeroacoustic (<20 Hz) behaviour of a generic wind turbine during a meteorological event with strong and rapid changes in wind speed and direction is investigated. A precursor simulation with the meteorological model system PALM is deployed to generate realistic inflow data. The simulated strong controller response of the wind turbine and the resulting aeroelastic behaviour are analysed. Finally, the low‐frequency sound emissions are evaluated and the influence of the different operating and flow parameters during the variable inflow is assessed. It is observed that the wind speed and, linked to it, the rotational speed as well as the turbulence intensity are the main influencing factors for the emitted low‐frequency sound power of the wind turbine. Yawed inflow, on the other hand, has little effect unless it changes the operational mode to load reduction, resulting in a swap of the main emitter from the blades to the tower.

“…Klein et al (2018) show that the blade-tower interaction, a key mechanism investigated in the following, is dominated by the blade-tower distance, which is massively reduced when the aeroelasticity of the blades is taken into account. The structural model of the I82 turbine in SIMPACK is adopted from Arnold et al (2020). The blades are modelled as nonlinear beams using 29 flexible beam elements (Timoshenko) per blade with Rayleigh damping.…”

Section: Cfd Model In Flowermentioning

confidence: 99%

Impact of the wind field at the complex-terrain site Perdigão on the surface pressure fluctuations of a wind turbine

Langner²,

Lutz

et al. 2022

Wind Energ. Sci.

Self Cite

Abstract. The surface pressure fluctuations, which are a source of low-frequency noise emissions, are numerically investigated on a 2 MW wind turbine under different inflow conditions. In order to evaluate the impact of a complex-terrain flow, a computational setup is presented that is aimed at reproducing a realistic flow field in the complex terrain in Perdigão, Portugal. A precursor simulation with the steady-state atmospheric computational fluid dynamics (CFD) code E-Wind is used, which was calibrated with meteorological (met) mast data to generate a site- and situation-specific inflow for a high-resolution delayed detached-eddy simulation (DDES) with FLOWer. A validation with lidar and met mast data reveals a good agreement of the flow field in the vicinity of the turbine in terms of mean wind speed and wind direction, whereas the turbulence intensity is slightly underestimated. Further downstream in the valley and on the second ridge, the deviations between simulation and measurement become significantly larger. The geometrically resolved turbine is coupled to the structural solver SIMPACK and simulated both in the complex terrain and in flat terrain with simpler inflows as reference. The surface pressure fluctuations are evaluated on the tower and blades. It is found that the periodic pressure fluctuations at the tower sides and back are dominated by vortex shedding, which strongly depends on the inflow and is reduced by inflow turbulence. However, the dominant pressure fluctuations on the upper part of the tower, which are caused by the blade–tower interaction, remain almost unchanged by the different inflows. The predominant pressure fluctuations on the blades occur with the rotation frequency. They are caused by a combination of rotor tilt, vertical wind shear and inclined flow and are thus strongly dependent on the inflow and the surrounding terrain. The inflow turbulence masks fluctuations at higher harmonics of the blade–tower interaction with its broadband characteristic caused by the interaction of the leading edge and the inflow turbulence.