Comparison of Methods to Derive Radial Wind Speed from a Continuous-Wave Coherent Lidar Doppler Spectrum

Held, Dominique Philipp; Mann, Jakob

doi:10.5194/amt-2018-229

Cited by 4 publications

(9 citation statements)

References 7 publications

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“…We also account for the lidar probe volume. The lidar Doppler spectrum S(v r , t) is (Held and Mann, 2018)…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…12(a), we show the probe volume filtering effect on the scanning pattern by plotting the ratio of the filtered to the unfiltered radial velocity variance from the simulations. Here, the filtered radial velocity variance is computed from the centroid-derived radial velocity, because the centroid method experiences the most turbulence attenuation caused by the probe volume (Held and Mann, 2018). The filtering effect due to probe volume is very similar throughout the pattern.…”

Section: Radial Velocity Variancementioning

confidence: 99%

“…As a consequence of the first effect, a lidar estimates turbulence essentially through a low pass-filter and cannot detect high frequency variations, which yields the so-called 'filtered variances'. Held and Mann (2018) showed that different methods of deriving the radial velocity from the lidar Doppler spectrum influence the degree of the turbulence attenuation. We explore the ability of these methods for turbulence estimation with the SpinnerLidar measurements.…”

Section: Introductionmentioning

confidence: 99%

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Turbulence statistics from three different nacelle lidars

Peña

Mann

2021

Preprint

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Abstract. Atmospheric turbulence can be characterized by the Reynolds stress tensor, which consists of the second-order moments of the wind field components. Most of the commercial nacelle lidars cannot estimate all components of the Reynolds stress tensor due to their limited number of beams; most can estimate the along-wind velocity variance relatively well. Other components are however also important to understand the behavior of, e.g., the vertical wind profile and meandering of wakes. The SpinnerLidar, a research lidar with multiple beams and a very high sampling frequency, was deployed together with two commercial lidars in a forward-looking mode on the nacelle of a Vestas V52 turbine to scan the inflow. Here, we compare the lidar-derived turbulence estimates with those from a sonic anemometer using both numerical simulations and measurements from a nearby mast. We show that from these lidars, the SpinnerLidar is the only one able to retrieve all Reynolds stress components. For the two- and four-beam lidars, we study different methods to compute the along-wind velocity variance. By using the SpinnerLidar's Doppler spectra of the radial velocity, we can partly compensate for the lidar's probe volume averaging effect and thus reduce the systematic error of turbulence estimates. We find that the variances of the radial velocities estimated from the maximum of the Doppler spectrum are less affected by the lidar probe volume compared to those estimated from the median or the centroid of the Doppler spectrum.

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“…We also account for the lidar probe volume. The lidar Doppler spectrum S(v r , t) is (Held and Mann, 2018)…”

Section: Numerical Simulationsmentioning

confidence: 99%

Section: Radial Velocity Variancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Turbulence statistics from three different nacelle lidars

Peña

Mann

2021

Preprint

Self Cite

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“…Different frequency estimators can yield less turbulence attenuation (Held and Mann, 2018). The Fourier transformation of the weighting function (eq.…”

Section: Rews Estimated From Lidar Measurementsmentioning

confidence: 99%

“…The lidar measurements have been simulated using eq. 14, however due to the finite size of the boxes the integration has been truncated at ±10z R from the focus point; details can be found in Held and Mann (2018). The two lidar systems presented in tab.…”

Section: Model Implementation and Validation Against Simulationsmentioning

confidence: 99%

Lidar Estimation of Rotor-Effective Wind Speed – An Experimental Comparison

Held¹,

Mann²

2019

Preprint

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Abstract. Lidar systems have the potential of alleviating structural loads on wind turbines by providing a preview of the incoming wind field to the control system. For a collective pitch controller the important quantity of interest is the rotor-effective wind speed (REWS). In this study, we present a model of the coherence between the REWS and its estimate from continuous-wave nacelle-mounted lidar systems. The model uses the spectral tensor definition of the Mann model. Model results were compared to field data gathered from a 2- and 4-beam nacelle lidar mounted on a wind turbine. The comparison shows close agreement for the coherence and the data fits better to the proposed model than to a model based on the Kaimal turbulence model, which underestimates the coherence. Inflow conditions with larger length scales led to a higher coherence between REWS and lidar estimates than inflow turbulence of smaller length scale. When comparing the two lidar systems, it was shown that the 4-beam lidar is able to resolve small turbulent structures with a higher degree of coherence. Further, the advection speed by which the turbulent structures are transported from measurement to rotor plane can be estimated by 10 minute averages of the lidar estimation of REWS. The presented model can be used as a computationally efficient tool to optimize the position of the lidar focus points in order to maximize the coherence.

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Updates on the OpenFAST Lidar Simulator

Guo

Schlipf

Zhu³

et al. 2022

J. Phys.: Conf. Ser.

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Lidar systems are able to measure the wind speed remotely by detecting the aerosol movement caused by wind. A nacelle-based lidar system scanning the wind in front of a wind turbine can provide a preview of the incoming wind before the wind interacts with the turbine. Implementing a realistic lidar simulator into the wind turbine aero-elastic simulation tool can be beneficial for various wind energy related fields, such as lidar-assisted control, load validation, and load monitoring. In previous work, a lidar simulation module has been integrated into the open-source aero-elastic simulation tool OpenFAST, covering already lidar characteristics like different scan patterns, the volume averaging along the beam, and the coupling with the nacelle motion due to turbine tower dynamics. This paper focuses on adding further features to the lidar simulation module of OpenFAST to make the lidar simulation more realistic: the evolving turbulence, the blade blockage effect, and the adjustable data availability. Further, the wind preview quality with the new features is assessed.

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Comparison of Methods to Derive Radial Wind Speed from a Continuous-Wave Coherent Lidar Doppler Spectrum

Cited by 4 publications

References 7 publications

Turbulence statistics from three different nacelle lidars

Turbulence statistics from three different nacelle lidars

Lidar Estimation of Rotor-Effective Wind Speed – An Experimental Comparison

Updates on the OpenFAST Lidar Simulator

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