scholarly journals Applying a Random Time Mapping to Mann modelled turbulence for the generation of intermittent wind fields

2021 ◽  
Author(s):  
Khaled Yassin ◽  
Arne Helms ◽  
Daniela Moreno ◽  
Hassan Kassem ◽  
Leo Höning ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Field ◽  
Extreme Values ◽  
Random Time ◽  
Spatial Correlations ◽  
Wind Fields ◽  
Mapping Procedure ◽  
Velocity Increment ◽  
Non Gaussian ◽  
New Time

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.

scholarly journals Wind turbine load dynamics in the context of turbulence intermittency

2019 ◽  
Vol 4 (4) ◽  
pp. 581-594 ◽  
Author(s):  
Carl Michael Schwarz ◽  
Sebastian Ehrich ◽  
Joachim Peinke
Keyword(s):  
Wind Turbine ◽  
Design Guidelines ◽  
Elastic Model ◽  
Spatial Correlations ◽  
Wind Fields ◽  
Wind Structure ◽  
Turbulence Intermittency ◽  
Velocity Increments ◽  
Fatigue Loads ◽  
Non Gaussian

Abstract. The importance of a high-order statistical feature of wind, which is neglected in common wind models, is investigated: non-Gaussian distributed wind velocity increments related to the intermittency of turbulence and their impact on wind turbine dynamics and fatigue loads are the focus. Gaussian and non-Gaussian synthetic wind fields obtained from a continuous-time random walk model are compared and fed to a common aero-servo-elastic model of a wind turbine employing blade element momentum (BEM) aerodynamics. It is discussed why and how the effect of the non-Gaussian increment statistics has to be isolated. This is achieved by assuring that both types feature equivalent probability density functions, spectral properties and coherence, which makes them indistinguishable based on wind characterizations of common design guidelines. Due to limitations in the wind field genesis, idealized spatial correlations are considered. Three examples with idealized; differently sized wind structures are presented. A comparison between the resulting wind turbine loads is made. For the largest wind structure sizes, differences in the fatigue loads between intermittent and Gaussian are observed. These are potentially relevant in a wind turbine certification context. Subsequently, the dependency of this intermittency effect on the field's spatial variation is discussed. Towards very small structured fields, the effect vanishes.

scholarly journals Fatigue Assessment of Monopile Supported Offshore Wind Turbine under Non-Gaussian Wind Field

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Bing Li ◽  
Kang Rong ◽  
Haifeng Cheng ◽  
Yongxin Wu
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Fatigue Damage ◽  
Wind Turbines ◽  
Wind Field ◽  
Pile Foundation ◽  
Offshore Wind ◽  
Wind Fields ◽  
Offshore Wind Turbines ◽  
Non Gaussian

The vibration of offshore wind turbines caused by external loads is significant, which will cause fatigue damage to offshore wind turbines. Wind load is the main load during the operation period of the wind turbine, and available studies have shown that the external wind field often exhibits certain non-Gaussian characteristics. This article aims to obtain the fatigue assessment of the monopile foundation of the wind turbine under the non-Gaussian wind fields. A 5 MW wind turbine is selected in this article, and OpenFAST is applied to simulate the wind load. By comparing the Mises stress time histories of the pile foundation at a different depth, the fatigue analysis of the critical spots of the pile foundation is obtained. In the analysis of fatigue damage, the rain flow counting method is adopted, and the two-segment S-N curve is selected to analyze the fatigue life of the critical spots. The results show that, by taking the non-Gaussian characteristic of the wind field into account, the fatigue life of the monopile foundation decreases. Therefore, attention should be paid to the influence of non-Gaussian characteristics of wind fields on the fatigue life of monopile-supported wind turbines.

scholarly journals Wind turbine load dynamics in the context of turbulence intermittency

2019 ◽  
Author(s):  
Carl Michael Schwarz ◽  
Sebastian Ehrich ◽  
Joachim Peinke
Keyword(s):  
Wind Turbine ◽  
Design Guidelines ◽  
Spatial Correlations ◽  
Wind Fields ◽  
Wind Structure ◽  
Turbulence Intermittency ◽  
Velocity Increments ◽  
Fatigue Loads ◽  
Non Gaussian ◽  
Blade Element

Abstract. The importance of a high order statistical feature of wind, which is neglected in common wind models, is investigated: Non-Gaussian distributed wind velocity increments related to the intermittency of turbulence and their impact on wind turbines dynamics and fatigue loads are in the focus. Two types of synthetic wind fields obtained from a Continuous-Time-Random Walk model are compared and fed to a common Blade-Element/Momentum theory based aero-servo-elastic wind turbine model. It is discussed why and how the effect of the non-Gaussian increment statistics has to be isolated. This is achieved by assuring that both types feature equivalent probability density functions, spectral properties and coherence, which makes them indistinguishable based on wind characterizations of common design guidelines. Due to limitations in the wind field genesis idealized spatial correlations are considered. Three examples with idealized, differently sized wind structures are presented. A comparison between the resulting wind turbine loads is made. For the largest wind structure sizes differences in the fatigue loads between intermittent and Gaussian are observed. These are potentially relevant in a wind turbine certification context. Subsequently, the dependency of this intermittency effect on the field's spatial variation is discussed. Towards very small structured fields the effect vanishes.

scholarly journals Long-range WindScanner System

2016 ◽  
Author(s):  
Nikola Vasiljevic ◽  
Guillaume Lea ◽  
Michael Courtney ◽  
Jean-Pierre Cariou ◽  
Jakob Mann ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Long Range ◽  
Wind Field ◽  
Wind Farms ◽  
Laser Beams ◽  
Wind Fields ◽  
High Quality ◽  
Technical Aspects ◽  
Points Of Interest ◽  
Field Campaigns

In this paper, the technical aspects of a multi-lidar instrument, the long-range WindScanner system, will be presented accompanied by an overview of the results from several field campaigns. The long-range WindScanner system consists of three spatially separated coherent Doppler scanning lidars and a remote master computer that coordinates them. The lidars were carefully engineered to perform arbitrary and time controlled scanning trajectories. Their wireless coordination via the master computer allows achieving and maintaining lidars’ synchronization within ten milliseconds. As a whole, the long-range WindScanner system can measure an entire wind field by emitting and directing three laser beams to intersect, and then by moving the beam intersection over the points of interest. The long-range WindScanner system was developed to tackle the need for high-quality observations of wind fields from scales of modern wind turbine and wind farms. It has been in operation since 2013.

Simulation of Thunderstorm Downbursts and Associated Wind Turbine Loads

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Hieu Huy Nguyen ◽  
Lance Manuel ◽  
Jason Jonkman ◽  
Paul S. Veers
Keyword(s):  
Wind Turbine ◽  
Wind Field ◽  
Control Strategies ◽  
Mean Field ◽  
System Response ◽  
Illustrative Case ◽  
Wind Fields ◽  
Wind Speeds ◽  
Wind Turbine Control ◽  
Utility Scale

This study is focused on simulation of thunderstorm downbursts and associated wind turbine loads. We first present a thunderstorm downburst model, in which the wind field is assumed to result from the summation of an analytical mean field and stochastic turbulence. The structure and evolution of the downburst wind field based on the analytical model are discussed. Loads are generated using stochastic simulation of the aeroelastic response for a model of a utility-scale 5-MW turbine. With the help of a few assumptions, particularly regarding control strategies, we address the chief influences of wind velocity fields associated with downbursts—namely, large wind speeds and large, rapid wind direction changes—by considering different storm scenarios and studying associated turbine loads. These scenarios include, first, an illustrative case to understand details related to the turbine response simulation; this is followed by a study involving a different storm touchdown location relative to the turbine as well as a critical case where a shutdown sequence is included. Results show that the availability of and assumptions in wind turbine control systems during a downburst clearly influence overall system response. Control system choices can significantly mitigate turbine loads during downbursts. Results also show that different storm touchdown locations result in distinct characteristics in inflow wind fields and, hence, in contrasting turbine response.

scholarly journals Reconstruction of Three-Dimensional Dynamic Wind-Turbine Wake Wind Fields with Volumetric Long-Range Wind Doppler LiDAR Measurements

2019 ◽  
Vol 11 (22) ◽  
pp. 2665 ◽  
Author(s):  
Beck ◽  
Kühn
Keyword(s):  
Wind Turbine ◽  
Long Range ◽  
Wind Field ◽  
Three Dimensional ◽  
Wake Flow ◽  
Wind Fields ◽  
Wake Field ◽  
Eddy Simulation ◽  
Lidar Measurements ◽  
Set Up

This paper presents a method for reconstructing the wake wind field of a wind turbine based on planar light detection and ranging (LiDAR) scans crossing the wake transversally in the vertical and horizontal directions. Volumetric measurements enable the study of wake characteristics in these two directions. Due to a lack of highly resolved wind speed measurements as reference data, we evaluate the reconstruction in a synthetic environment and determine the reconstruction errors. The wake flow of a multi-megawatt wind turbine is calculated within a 10-min large-eddy simulation (LES) for high-thrust loading conditions. We apply a numerical LiDAR simulator to this wake wind field to achieve realistic one-dimensional velocity data. We perform a nacelle-based set-up with combined plan position indicator and range height indicator scans with eight scanning velocities each. We temporally up-sample the synthetic LiDAR data with a weighted combination of forward- and backward-oriented space–time conversion to retrospectively extract high-resolution wake characteristic dynamics. These dynamics are used to create a dynamic volumetric wake deficit. Finally, we reconstruct the dynamic wake wind field in three spatial dimensions by superposing an ambient wind field with the dynamic volumetric wake deficit. These results demonstrate the feasibility of wake field reconstruction using long-range LiDAR measurements.

scholarly journals Evaluation and Post-Processing of Reanalysis Wind Speeds for Renewable Energy Applications

2021 ◽  
Author(s):  
Sebastian Brune ◽  
Jan D. Keller ◽  
Sabrina Wahl
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Turbine ◽  
Wind Field ◽  
Lower Boundary ◽  
Horizontal Resolution ◽  
Lower Atmosphere ◽  
Wind Fields ◽  
Wind Model ◽  
Lower Boundary Layer

<p>The correct spatio-temporal representation of wind speed is of large interest for the wind energy sector. Therefore, this study compares wind measurements in different heights from several locations in Central Europe with two global (ERA5, MERRA-2) and one regional reanalysis (COSMO-REA6). Employing a two-parameter Weibull distribution, the shape and scale parameters as well as mean, standard deviation and RMSE are investigated at and around common wind turbine hub height. We find that COSMO-REA6 best describes wind fields closer to the surface possibly due to its high horizontal resolution. Here, it also exhibits a good alignment with the diurnal cycle. However, for common wind turbine hub heights and above, ERA5 outperforms the other two reanalyses possibly due to its higher vertical resolution. MERRA-2 overestimates wind speed in the lower boundary layer at nearly all sites.</p><p>In the next step, a diagnostic and mass-consistent wind model is applied to the COSMO-REA6 wind field. The resolution of the wind field will be increased by a factor of 8 from originally 6 km to approximately 800 m. In addition to the vertical stability of the lower atmosphere, the orography on the finer grid and the corresponding effects are taken into account. We expect that especially in complex terrain the wind field will be corrected and thus should fit better to the observations. Channeling effects, shadowing and increased wind speed in exposed locations can be better represented. The new high-resolution wind field forms the basis for a statistical wind model to obtain post-processed wind estimates in the lower boundary layer. This approach will utilize generalized linear model and/or an artificial neural network techniques.</p>

scholarly journals Engineering Comprehensive Model of Complex Wind Fields for Flight Simulation

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 145
Author(s):  
Jianwei Chen ◽  
Liangming Wang ◽  
Jian Fu ◽  
Zhiwei Yang
Keyword(s):  
Wind Field ◽  
Three Dimensional ◽  
Great Influence ◽  
Spatial Location ◽  
Flight Simulation ◽  
Comprehensive Model ◽  
Flight Trajectory ◽  
Wind Fields ◽  
Wind Field Simulation ◽  
Low Level Jet

A complex wind field refers to the typical atmospheric disturbance phenomena existing in nature that have a great influence on the flight of aircrafts. Aimed at the issues involving large volume of data, complex computations and a single model in the current wind field simulation approaches for flight environments, based on the essential principles of fluid mechanics, in this paper, wind field models for two kinds of wind shear such as micro-downburst and low-level jet plus three-dimensional atmospheric turbulence are established. The validity of the models is verified by comparing the simulation results from existing wind field models and the measured data. Based on the principle of vector superposition, three wind field models are combined in the ground coordinate system, and a comprehensive model of complex wind fields is established with spatial location as the input and wind velocity as the output. The model is applied to the simulated flight of a rocket projectile, and the change in the rocket projectile’s flight attitude and flight trajectory under different wind fields is analyzed. The results indicate that the comprehensive model established herein can reasonably and efficiently reflect the influence of various complex wind field environments on the flight process of aircrafts, and that the model is simple, extensible, and convenient to use.

Simulation of the wind fields over complex terrain with coupling of CFD and WRF

2021 ◽  
pp. 1-12
Author(s):  
Xiaoyu Luo ◽  
Yiwen Cao
Keyword(s):  
Wind Speed ◽  
Wind Field ◽  
Complex Terrain ◽  
Civil Engineering ◽  
Meteorological Data ◽  
Mass Conservation ◽  
Coupling Method ◽  
Wind Fields ◽  
Civil Structures ◽  
Civil Engineers

In the field of civil engineering, the meteorological data available usually do not have the detailed information of the wind near a certain site. However, the detailed information of the wind field during typhoon is important for the wind-resistant design of civil structures. Furthermore, the resolution of the meteorological data available by the civil engineers is too coarse to be applicable. Therefore it is meaningful to obtain the detailed information of the wind fields based on the meteorological data provided by the meteorological department. Therefore, in the present study, a one-way coupling method between WRF and CFD is adopted and a method to keep the mass conservation during the simulation in CFD is proposed. It is found that using the proposed one-way coupling method, the predicted wind speed is closer to the measurement. And the curvature of the wind streamline during typhoon is successfully reproduced.

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