the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Applying a Random Time Mapping to Mann modelled turbulence for the generation of intermittent wind fields
Khaled Yassin
Arne Helms
Daniela Moreno
Hassan Kassem
Leo Höning
Laura J. Lukassen
Abstract. A new approach to derive a synthetic wind field model which combines spatial correlations from the Mann model and intermittency is introduced. The term intermittency describes the transition from Gaussian to non-Gaussian velocity increment statistics at small scales, where non-Gaussian velocity increment statistics imply a higher probability for extreme values than a Gaussian distribution. The presented new model is named the Time-mapped Mann model. The intermittency is introduced by applying a special random time-mapping procedure to the regular Mann model. The Time-mapping procedure is based on the so-called Continuous-time random walk model. As will be shown, the new Time-mapped Mann field reflects spatial correlations from the Mann model in the plane perpendicular to flow direction and temporal intermittency. In a first wind turbine study, the new Time-mapped Mann field and a regular Mann field are used as inflow to a wind turbine in a Blade Element Momentum simulation. It is shown that the wind field intermittency carries over to the loads of the wind turbine, and, thus, shows the importance of carefully modeling synthetic wind fields.
Khaled Yassin et al.
Status: final response (author comments only)
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RC1: 'Comment on wes-2021-139', Anonymous Referee #1, 13 Jan 2022
This manuscript presents a time-mapped Mann model to derive a synthetic wind field model. Wind field modeling plays an important role in wind energy studies. In general, it is an interesting topic.
1) The writing needs significant improvement. Please use scientific expressions in the manuscript.
2) There are some state-of-the-art field investigations on the influence of turbulence on the wind turbine structural response. Please discuss your results with the field measurement results.
3) line 100: Please provide more information on how to choose the two points. Any restrictions about the distance between these two points.
4) Fig.1: please add error bars on the measurement results since you have 500-time series samples for analysis.
5) Sec 2.2 & Sec 2.3: please make it more concise.
6) Fig. 8: The curves are shifted vertically for visualization. Please provide more detailed information.
7) Why did you select 10% as the turbulence intensity level?
8) Why did you choose a fixed pitch and fixed speed wind turbine for the simulation? Most current utility-scale wind turbines are variable speed and variable pitch regulated.
9) The mean wind speed in Table 3 is extremely high (20 m). In most wind farms, the annual average wind speed won't exceed 12 m/s. Please explain and also add cases with lower speeds.
10) Please add wind shear as well in the FAST simulations as well. It may have a larger impact on the turbine structural response than turbulence.
11) Please add more statistic information about 500 sample datasets in the Appendix, including but not limited to wind direction, wind speed, turbulence level.
Citation: https://doi.org/10.5194/wes-2021-139-RC1 - AC1: 'Reply on RC1', Khaled Yassin, 24 Mar 2022
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RC2: 'Comment on wes-2021-139', Anonymous Referee #2, 17 Jan 2022
The comment was uploaded in the form of a supplement: https://wes.copernicus.org/preprints/wes-2021-139/wes-2021-139-RC2-supplement.pdf
- AC2: 'Reply on RC2', Khaled Yassin, 24 Mar 2022
Khaled Yassin et al.
Khaled Yassin et al.
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