scholarly journals Comments on “Wind Gust Detection and Impact Prediction for Wind Turbines”

2018 ◽  
Vol 10 (10) ◽  
pp. 1625 ◽  
Author(s):  
Shane Mayor ◽  
Pierre Dérian
Keyword(s):  
Motion Estimation ◽  
Wind Turbines ◽  
Cross Correlation ◽  
Velocity Fields ◽  
Estimation Methods ◽  
Wind Gust ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Impact Prediction ◽  
Vector Wind

We refute statements in “Zhou, K., et al. Wind gust detection and impact prediction for wind turbines. Remote Sens. 2018, 10, 514.” the impracticality of motion estimation methods to derive two-component vector wind fields from single scanning aerosol lidar data. Our assertion is supported by recently published results on the performance of two image-based motion estimation methods: cross-correlation (CC) and wavelet-based optical flow (WOF). The characteristics and performances of CC and WOF are compared with those of a two-dimensional variational (2D-VAR) method that was applied to radial velocity fields from a single scanning Doppler lidar. The algorithmic aspects of WOF and 2D-VAR are reviewed and we conclude that these two approaches are in fact similar and practical.

scholarly journals Wind Gust Detection and Impact Prediction for Wind Turbines

2018 ◽  
Vol 10 (4) ◽  
pp. 514 ◽  
Author(s):  
Kai Zhou ◽  
Nihanth Cherukuru ◽  
Xiaoyu Sun ◽  
Ronald Calhoun
Keyword(s):  
Wind Turbines ◽  
Wind Gust ◽  
Impact Prediction

scholarly journals ESTIMATING SURFACE VELOCITIES IN THE SOUTHERN BRAZILIAN AND URUGUAYAN CONTINENTAL SHELVES USING THE MAXIMUM CROSS-CORRELATION METHOD

2017 ◽  
Vol 16 (1) ◽  
pp. 46
Author(s):  
J. Costi ◽  
E. P. Kirinus ◽  
W. C. Marques ◽  
C. A. E. Garcia ◽  
C. Fujita
Keyword(s):  
Cross Correlation ◽  
Correlation Method ◽  
Velocity Fields ◽  
Time Interval ◽  
Wind Fields ◽  
Continental Shelves ◽  
Image Pairs ◽  
Ocean Color Imagery ◽  
Sequential Images ◽  
Diffusive Processes

The present study investigates the viability of using the maximum cross- correlation method on ocean color imagery to estimate surface velocities on the Southern Brazilian and Uruguayan continental shelf. The method searches for maximum correlation areas in two sequential images, determining the displacement of oceanographic features within the time interval of the images acquisition. We use the NWL550 parameter of MODIS-Aqua imagery, once it is well correlated with the total suspended matter in the water and provides relatively well-defined optical features on the Southern Brazilian and Uruguayan continental shelves. The estimated velocity fields showed a preferential direction northward, with average intensities between 0.06 m/s and 0.11 m/s. The frequent cloud coverage and the diffusive processes restrict the number of image pairs suitable for the analysis. Nevertheless, the method showed potential for investigating the current velocity fields on the study area, as the estimates are in agreement with the wind fields and the velocities' intensities are well within the values previously described in the literature for the region.

scholarly journals Estimation of Subpixel Motion Using Bispectrum

2008 ◽  
Vol 2008 ◽  
pp. 1-5 ◽  
Author(s):  
El Mehdi Ismaili Aalaoui ◽  
Elhassane Ibn-Elhaj
Keyword(s):  
Motion Estimation ◽  
Frequency Domain ◽  
Video Processing ◽  
Cross Correlation ◽  
Image Sequences ◽  
Experimental Results ◽  
Phase Correlation ◽  
Estimation Methods ◽  
Noisy Image ◽  
Better Than

Motion estimation techniques are widely used in today's video processing systems. The frequently used techniques are frequency-domain motion estimation methods, most notably phase correlation (PC). If the image frames are corrupted by Gaussian noises, then cross-correlation and related techniques do not work well. In this paper, however, we have studied this topic from a viewpoint different from the above. Our scheme is based on the bispectrum method for sub-pixel motion estimation of noisy image sequences. Experimental results show that our proposed method performs significantly better than PC technique.

Exploiting Bidirectional Power Flow Control to Capture Wind Gust Power in Small and Medium Wind Turbines

2021 ◽  
Author(s):  
B. M. Gavgani ◽  
T. Staessens ◽  
J. V. Damme ◽  
J. D. M. De Kooning ◽  
D. Bozalakov ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbines ◽  
Power Flow ◽  
Wind Gust ◽  
Power Flow Control ◽  
Bidirectional Power Flow

scholarly journals Characterizing wind gusts in complex terrain

2019 ◽  
Vol 19 (6) ◽  
pp. 3797-3819 ◽  
Author(s):  
Frederick Letson ◽  
Rebecca J. Barthelmie ◽  
Weifei Hu ◽  
Sara C. Pryor
Keyword(s):  
Wind Turbines ◽  
Complex Terrain ◽  
Probability Distributions ◽  
Wind Loading ◽  
Wind Gust ◽  
Wind Gusts ◽  
Sonic Anemometers ◽  
Vertical Displacements ◽  
Structural Loading ◽  
Good Agreement

Abstract. Wind gusts are a key driver of aerodynamic loading, especially for tall structures such a bridges and wind turbines. However, gust characteristics in complex terrain are not well understood and common approximations used to describe wind gust behavior may not be appropriate at heights relevant to wind turbines and other structures. Data collected in the Perdigão experiment are analyzed herein to provide a foundation for improved wind gust characterization and process-level understanding of flow intermittency in complex terrain. High-resolution observations from sonic anemometers and vertically pointing Doppler lidars are used to conduct a detailed study of gust characteristics with a specific focus on the parent distributions of nine gust parameters (that describe velocity, time, and length scales), their joint distributions, height variation, and coherence in the vertical and horizontal planes. Best-fit distributional forms for varying gust properties show good agreement with those from previous experiments in moderately complex terrain but generate nonconservative estimates of the gust properties that are of key importance to structural loading. Probability distributions of gust magnitude derived from vertically pointing Doppler lidars exhibit good agreement with estimates from sonic anemometers despite differences arising from volumetric averaging and the terrain complexity. Wind speed coherence functions during gusty periods (which are important to structural wind loading) are similar to less complex sites for small vertical displacements (10 to 40 m), but do not exhibit an exponential form for larger horizontal displacements (800 to 1500 m).

scholarly journals Identification of Aircraft Wake Vortex Based on SVM

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Weijun Pan ◽  
Zhengyuan Wu ◽  
Xiaolei Zhang
Keyword(s):  
Environmental Parameters ◽  
Classification Model ◽  
Support Vector ◽  
Wake Vortex ◽  
Doppler Lidar ◽  
Pulsed Doppler ◽  
Wind Fields ◽  
Wake Turbulence ◽  
Aircraft Wake ◽  
Separation Standards

The aircraft wake vortex has important influence on the operation of the airspace utilization ratio. Particularly, the identification of aircraft wake vortex using the pulsed Doppler lidar characteristics provides a new knowledge of wake turbulence separation standards. This paper develops an efficient pattern recognition-based method for identifying the aircraft wake vortex measured with the pulsed Doppler lidar. The proposed method is outlined in two stages. (i) First, a classification model based on support vector machine (SVM) is introduced to extract the radial velocity features in the wind fields by combining the environmental parameters. (ii) Then, grid search and cross-validation based on soft margin SVM with kernel tricks are employed to identify the aircraft wake vortex, using the test dataset. The dataset includes wake vortices of various aircrafts collected at the Chengdu Shuangliu International Airport from Aug 16, 2018, to Oct 10, 2018. The experimental results on dataset show that the proposed method can identify the aircraft wake vortex with only a small loss, which ensures the satisfactory robustness in detection performance.

scholarly journals Remote sensing of multi-level wind fields with high-energy airborne scanning coherent Doppler lidar

1998 ◽  
Vol 2 (2) ◽  
pp. 40 ◽  
Author(s):  
Jeffry Rothermel ◽  
Lisa D. Olivier ◽  
Robert M. Banta ◽  
R. Michael Hardesty ◽  
James N. Howell ◽  
...  
Keyword(s):  
Remote Sensing ◽  
High Energy ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Coherent Doppler Lidar ◽  
Multi Level

Estimating Spatial Velocity Statistics with Coherent Doppler Lidar

2002 ◽  
Vol 19 (3) ◽  
pp. 355-366 ◽  
Author(s):  
Rod Frehlich ◽  
Larry Cornman
Keyword(s):  
Radial Velocity ◽  
Spatial Scales ◽  
Energy Dissipation Rate ◽  
Doppler Lidar ◽  
Wind Fields ◽  
Velocity Statistics ◽  
Coherent Doppler Lidar ◽  
Spatial Velocity ◽  
Large Measurement ◽  
Turbulent Velocity Field

Abstract The spatial statistics of a simulated turbulent velocity field are estimated using radial velocity estimates from simulated coherent Doppler lidar data. The structure functions from the radial velocity estimates are processed to estimate the energy dissipation rate ε and the integral length scale Li, assuming a theoretical model for isotropic wind fields. The performance of the estimates are described by their bias, standard deviation, and percentiles. The estimates of ε2/3 are generally unbiased and robust. The distribution of the estimates of Li are highly skewed; however, the median of the distribution is generally unbiased. The effects of the spatial averaging by the atmospheric movement transverse to the lidar beam during the dwell time of each radial velocity estimate are determined, as well as the error scaling as a function of the dimensions of the total measurement region. Accurate estimates of Li require very large measurement domains in order to observe a large number of independent samples of the spatial scales that define Li.

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