Three-dimensional Wind Field Research Articles

Frontal Wind Field Retrieval Based on UHF Wind Profiler Radars and S-Band Radars Network

The three-dimensional wind field (WPR3D) and the multiple WPR3D (M-WPR3D) associated with the passage of a stationary front was derived from observations made by a network of eight wind profiler radars (WPR) being operated by the Korea Meteorological Administration during the summer “Jangma” season. The effectiveness of the WPR3D was determined through numerical model analysis and wind profilers at three sites, and the accuracy of the M-WPR3D was validated by comparing the trajectory of the radiosonde. The discontinuity of the wind field near the frontal interface was clearly retrieved and the penetration of the air mass in the southern front was detected. Compared with either the wind vector of three single wind profiler or a local data assimilation and predication system, the WPR3D wind field showed a wind speed accuracy of approximately 70% at an altitude of 1.5 km and underestimated the wind speed by 0.5–1.5 m s−1. The M-WPR3D with three S-band Doppler radars successfully retrieved the backing wind field as well as the pre-Jangma-frontal jet. The results of this study showed that severe weather can be effectively analyzed using a three-dimensional wind field generated on the basis of a remote sensing network.

Vibration control of horizontal axis offshore wind turbine blade using SMA stiffener

Modern multi-megawatt wind turbines have large flexible blades that often exhibit significant vibration when exposed to turbulent wind. The present study proposes longitudinal stiffening of blades to address this issue using tendon made of shape memory alloy. A reduced order model of the combined system is developed that incorporates blade stiffening. The nonlinear material behavior of the stiffener is modeled by combining the principle of thermodynamics with the constitutive model as proposed in the literature. Thus, super-elastic effects are utilized in active mode (i.e. using Jule heating with the help of current flow) to apply actuation force that opposes blade deformation. Three-dimensional wind field passing through the rotor plane is simulated using TurbSim package freely available from National Renewable Energy Laboratory, USA. Aerodynamic loads are computed using modified Blade Element Momentum theory and wave loads are simulated using Morison’s equation where wave time histories are simulated from the JONSWAP spectrum. Using these loads as input, the response of a benchmark wind turbine is simulated to show the performance of the proposed control strategy. Numerical results presented in this paper clearly demonstrate the efficiency and advantage of the SMA based stiffener to improve the vibration characteristics of the large turbine blades.

Short-term variation in atmospheric constituents associated with local front passage observed by a 3-D coherent Doppler lidar and in-situ aerosol/gas measurements

Abstract Local fronts, such as sea-breeze and land-breeze fronts, play an important role not only from a meteorological aspect but also for pollutant transport and mixing, in urban areas in particular. Due to the difficulty of measuring three-dimensional (3-D) wind fields, there are few studies focusing on short-term fine-scale spatial and temporal variations in aerosol and gas compositions associated with local front passage. At the end of November 2016, a 3-D coherent Doppler lidar was installed in Fukuoka city (33.55°N, 130.37°E), an urban area in Japan, and 3D-wind fields have been continuously measured since then. Two local fronts with typical density current structure were observed on 3 May and 29 June 2017. On 3 May 2017, there was a stepwise increase in concentrations of aerosol (particularly smaller size aerosol), black carbon (BC) and carbon monoxide (CO), supposedly of surface origin, at the passage of the local front. However, O3 content, which can be higher at higher altitudes, decreased. In another case on 29 June 2017, there was light rain in the early morning and all gas and aerosol contents were low before the passage of the front. At the front passage, there was a stepwise increase in aerosol, BC and CO contents as on 3 May, although O3 content gradually increased after sunrise and no clear change was observed in O3. Vertical aerosol observations by the Doppler lidar indicate that the depth of the front system on 29 June was much thinner (up to 300–400 m) than that on 3 May (up to ∼700 m), and the temperature decrease was larger than on 3 May. These facts suggest that the mixing of air masses within the system with those above or ahead of the system on 29 June was no stronger than on 3 May, and thus the aerosol and gas contents at the ground may be strongly affected by the vertical mixing/dilution of the system as well as by local emission.

An Improved Mass Consistent Model for Three-Dimensional Wind Field Construction

An improved diagnostic mass-consistent finite element model (FEM) has been developed to construct 3D wind fields over irregular terrain. Instead of using constant Gauss precision moduli over the whole domain in the existing mass-consistent models, the improved mass-consistent model adopts different Gauss precision moduli based on the terrain topography gradient associated with atmospheric boundary conditions. These terrain sensitive moduli resolve wind flows over large topographical obstacles more accurately than constant Gauss precision moduli. In this study, a terrain following mesh generator is developed based on digital elevation data from the U.S. Geological Survey, and the data linked to the modified mass-consistent FEM model. The improved model is validated and verified using a benchmark study for flow over a semicylinder. The model is then used to re-examine 3D wind fields previously simulated for the Nellis Dunes area near Las Vegas, NV. Results show that the improved mass consistent modeling system shows better agreement with the recorded meteorological tower data than the previous results obtained using constant moduli.

Nonlinear Aeroelastic Analysis of Large Wind Turbines Under Turbulent Wind Conditions

We investigate in this Paper the nonlinear aeroelastic response of large horizontal axis wind turbines under a stochastically simulated turbulent wind field, which is instantaneously sampled by the rotating and deforming blades of the rotor. The aeroelastic code combines the unsteady blade element momentum theory, equipped with several important corrections, with the displacement-based nonlinear finite element implementation of the geometrically exact beam theory. The structural model is both shearable and extensible and does not place any restrictions on the magnitudes of the configuration variables or those of the resulting one-dimensional strain measures. The aeroelastic coupling takes into account the beam axis deformations, elastic twist, and vibration-induced velocities. The three-component, three-dimensional turbulent wind field is obtained using the Mann spectrum, from which the instantaneously sampled wind speeds are extracted by spatiotemporal interpolation in the spirit of Taylor’s frozen turbulence hypothesis. The structural and unsteady aerodynamic analysis components of the aeroelastic code are validated using benchmark examples. A fully coupled nonlinear aeroelastic simulation is carried out for the National Renewable Energy Laboratory’s 5 MW research wind turbine. The influence of three-dimensional instantaneous sampling, transverse (lateral and vertical) components of turbulence, vertical wind shear, and flow unsteadiness on the aeroelastic response under turbulence is examined along with the effects of coupling parameters including the vibration-induced velocities and elastic twist of the rotor blades. The dominant frequency contributions in key aeroelastic response variables due to each of these effects are identified.

Vertical distribution and vortex structure of rotor wind field under the influence of rice canopy

Rotor unmanned aerial vehicle (UAV) for plant protection has been widely applied in China in recent years. As a unique and crucial parameter of rotor UAV, the distribution shape and law of rotor wind field determine the spatial distribution of spraying droplets and influence the outcome of low-altitude pesticide spraying. However, the exploration of the interaction between rice canopy and wind field as well as the vertical decay mechanism is still an uncharted field in the study of three-dimensional wind field. In this paper, the author acquired vertical wind speed through S pitot sensor array, wind speed sensors were installed to acquire vertical wind speed data in the canopy, 30 cm beneath the canopy and 60 cm beneath the canopy. Contour maps at three height levels with wind speed of equal difference were drawn to calculate the equivalent area (the area surrounded by the contour line and the upper boundary) and maximum wind field width, all of which are direct parameters represent the distribution pattern of different wind speeds at equal time span. Under the condition that rice plants are well-distributed with consistent density, as the height decays arithmetically, coefficient variance (CV) of equivalent area is no more than 5% with basically equal reduction in equivalent area, the vertical wind field formed by the decayed airflow as it travels through rice plants distributes hierarchically. The decay rate of equivalent area and wind speed follow linear relation. When the height reduces from Ptop to Pmedium, the decay rate monotonically changes from 47.9% to 8.4%. When the height reduces from Pmedium to Pbottom, the decay rate monotonically changes from 53.7% to 22.4%. The lower the height is, the greater the decay rate is. Having analyzed the abnormal data ranges, the author found that the vortex formed under the interaction of wind field and rice canopy is the primary cause of abnormal data. Moreover, an ideal cone model was built on the basis of the rotor area and decay rate of equivalent area at equal height. The cone model not only justifies the vortex structure of rotor wind field but also provides theoretical foundation for the permeability study of droplets in rice canopy and the study of pollination parameters.

Investigation of the impact of planetary boundary layer turbulence on the performance of onshore wind farm

Abstract In recent years, wind power has become the fastest growing renewable energy. In the wind power generation, wind energy assessment is also a crucial one, it is directly related to the layout and power generation forecast of a wind farm. Before a wind park is constructed, a site with high mean annual wind speeds in hub height has to be found. To analyse the wind resources at a potential wind park site the three-dimensional wind field has to be simulated. In this paper, accurate and reliable Computational Fluid Dynamics (CFD) simulations of wind flow over natural complex terrain in northern of Morocco have been performed. The Geographic Information System (GIS) is used to generate contour elevation data before can be directly imported into CAD to generate terraced three-dimensional topographic map of test area. The site is characterized regarding its flow features and the suitability for a wind turbine test field. An improved delayed detached eddy simulation (IDDES) was employed using measurement data to generate generic turbulent inflow. A good agreement of the wind profiles between the different approaches was reached. The terrain slope leads to a speed up, a change of turbulence intensity as well as to flow angle variations. For the numerical simulation the Open Source Computational Fluid Dynamics (CFD) Toolbox OpenFOAM (Open Field Operation and Manipulation) was used. It is a compressible finite volume flow solver using block-structured grids and featuring a wide range of turbulence models. This type of analysis may help in preliminary assessments and expedite the site selection process.

Wind velocity distribution reconstruction using CFD database with Tucker decomposition and sensor measurement

Wind forecasting holds the key to the management of wind power. Previous vector or matrix wind forecast methods may not best reflect the intrinsic inter relationship among the wind velocity components of a three-dimensional wind field. Alternatively, a tensor-based model is developed to reconstruct the wind velocity distribution within a short period of time, enabling a new way for wind forecasting. A third-order CFD database is established by CFD simulations and the Tucker decomposition is used to obtain the tensor basis off site. Then in real time, the tensor basis can be employed to rapidly reconstruct wind velocity distributions in any direction, which can also form a new way to reconstruct wind velocity distribution in 3-D spaces. A comparison of the maximum and relative reconstruction errors shows that the newly proposed method performs better than the authors' previously published wind field reconstruction method. The influences of sampling rate, noise level and sensor distributions on the reconstruction error are also discussed in this paper. Finally, a wind tunnel experiment is carried out to evaluate the accuracy of the proposed method, and in most cases, the experimental results show that relative errors drop around 0.03%-0.4% and maximum errors drop around 0.02%-1.7% when using the newly proposed method.

Numerical Simulation and Analysis on Spray Drift Movement of Multirotor Plant Protection Unmanned Aerial Vehicle

In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.

Status and Prospects of Marine Wind Observations from Geostationary and Polar-Orbiting Satellites for Tropical Cyclone Studies

Satellite-derived sea surface winds (SSWs) and atmospheric motion vectors (AMVs) over the global ocean, particularly including the areas in and around tropical cyclones (TCs), have been provided in a real-time and continuous manner. More and better information is now derived from technologically improved multiple satellite missions and wind retrieving techniques. The status and prospects of key SSW products retrieved from scatterometers, passive microwave radiometers, synthetic aperture radar, and altimeters as well as AMVs derived by tracking features from multiple geostationary satellites are reviewed here. The quality and error characteristics, limitations, and challenges of satellite wind observations described in the literature, which need to be carefully considered to apply the observations for both operational and scientific uses, i.e., assimilation in numerical weather forecasting, are also described. Additionally, ongoing efforts toward merging them, particularly for monitoring three-dimensional TC wind fields in a real-time and continuous manner and for providing global profiles of high-quality wind observations with the new mission are introduced. Future research is recommended to develop plans for providing more and better SSW and AMV products in a real-time and continuous manner from existing and new missions.

A Variation Method for Retrieval of Three-Dimensional Wind Field by Bistatic Doppler Weather Radar Network

A variational method for the retrieval of 3D wind field by bistatic Doppler radar network is developed, and its performance is evaluated. This bistatic Doppler weather radar network consists of one X-band Doppler radar and one passive low-gain bistatic receiver. To allow for measurement error, this method uses the two radial velocities as weak constraints and uses the continuity equation as a strong constraint in a cost function. Improvements are brought to the classical upward integration of the continuity equation, using a weighted combination of upward and downward integrations and its adjoint. The wind field retrieval experiments are carried out by the actual observation data, and compared with the wind filed retrieved by the two Doppler radars. The results show that the wind field is very close, and the synchronous observation technology of the bistatic Doppler radar network is reasonable, which has the potential application in real-time detection of 3D wind field, especially for detecting near surface wind field.

Development and application of a simulator for offshore wind turbine blades installation

In an offshore environment, offshore wind energy resources are more available and stable, but the investment cost is much higher than that of onshore wind. The installation cost is a crucial factor of the investment. With the increasing number of planned and approved offshore wind farms, offshore wind turbine installation and relevant operations have received tremendous attention. Therefore, expediting the turbine-structure mating operations through a higher level of automation in offshore wind turbine installations may provide important economic benefits. To achieve a higher automation level and reduce the weather waiting time during the installation of offshore wind turbines, a flexible simulation-verification framework with high fidelity is needed. However, state-of-the-art wind turbine numerical analysis code is neither convenient nor open enough for applications concerning the design and verification of control algorithms. MATLAB/Simulink is among the most widely utilized numerical platforms by control engineers and researchers. This paper describes the development of a modularized blade installation simulation toolbox for the purpose of control design in MATLAB/Simulink. The toolbox can be used to simulate several blade installation configurations, both onshore and offshore. The paper presents the key features and equations of the different modules, exemplified by a single blade installation operation. Code-to-code verification results are presented and discussed with both quasi-steady wind and three-dimensional turbulent wind field.

Mitigation of offshore wind turbine responses under wind and wave loading: Considering soil effects and damage

The present paper studies the mitigation of monopile offshore wind turbines subjected to wind and wave loading. Soil effects (SE) and damage are considered. A semiactive tuned mass damper (STMD) capable of retuning its natural frequency and damping property in real time is utilized to mitigate the nacelle/tower top dynamic response. Based on the Euler–Lagrangian equation, an analytical model of the wind turbine coupled with an STMD is established wherein the interaction between the blades and the tower is modeled. Wind turbulence is generated via mapping a three-dimensional wind field profile onto the rotating blades. Aerodynamic loading is computed using the blade element momentum method where the Prandtl's tip loss factor and the Glauert correction are considered. Wave loading is computed using Morison's equation together with the strip theory. The National Renewable Energy Laboratory monopile 5-MW baseline wind turbine model is employed to examine the performance of the STMD. It is found that the SE and damage presence in the foundation or/and the tower can change the dominant frequency, thereby rendering the conventional TMD detuned and ineffective. In comparison, the STMD retuned in real time by the proposed algorithm can mitigate the nacelle/tower and foundation response more effectively with a smaller stroke. Results indicate that the STMD has significant effectiveness improvement over the TMD when the SE and/or damage are considered.

CFD three dimensional wake analysis in complex terrain

Even if wind energy technology is nowadays fully developed, the use of wind energy in very complex terrain is still challenging. In particular, it is challenging to characterize the combination effects of wind ow over complex terrain and wake interactions between nearby turbines and this has a practical relevance too, for the perspective of mitigating anomalous vibrations and loads as well improving the farm efficiency. In this work, a very complex terrain site has been analyzed through a Reynolds-averaged CFD (Computational Fluid Dynamics) numerical wind field model; in the simulation the inuence of wakes has been included through the Actuator Disk (AD) approach. In particular, the upstream turbine of a cluster of 4 wind turbines having 2.3 MW of rated power is studied. The objective of this study is investigating the full three-dimensional wind field and the impact of three-dimensionality on the evolution of the waked area between nearby turbines. A post-processing method of the output of the CFD simulation is developed and this allows to estimate the wake lateral deviation and the wake width. The reliability of the numerical approach is inspired by and crosschecked through the analysis of the operational SCADA (Supervisory Control and Data Acquisition) data of the cluster of interest.

Kinematic and Polarimetric Radar Observations of the 10 May 2010, Moore–Choctaw, Oklahoma, Tornadic Debris Signature

Tornadoes are capable of lofting large pieces of debris that present irregular shapes, near-random orientations, and a wide range of dielectric constants to polarimetric radars. The unique polarimetric signature associated with lofted debris is called the tornadic debris signature (TDS). While ties between TDS characteristics and tornado- and storm-scale kinematic processes have been speculated upon or investigated using photogrammetry and single-Doppler analyses, little work has been done to document the three-dimensional wind field associated with the TDS. Data collected by the Oklahoma City, Oklahoma (KTLX), and Norman, Oklahoma (KOUN), WSR-88D S-band radars as well as the University of Oklahoma’s (OU) Advanced Radar Research Center’s Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME) C-band radar are used to construct single- and dual-Doppler analyses of a tornadic supercell that produced an EF4 tornado near the towns of Moore and Choctaw, Oklahoma, on 10 May 2010. This study documents the spatial distribution of polarimetric radar variables and how each variable relates to kinematic fields such as vertical velocity and vertical vorticity. Special consideration is given to polarimetric signatures associated with subvortices within the tornado. An observation of negative differential reflectivity ([Formula: see text]) at the periphery of tornado subvortices is presented and discussed. Finally, dual-Doppler wind retrievals are compared to single-Doppler axisymmetric wind fields to illustrate the merits of each method.

Novel Scanning Strategy for Future Spaceborne Doppler Weather Radar With Application to Tropical Cyclones

Severe tropical cyclones (TCs) are one of the most devastating natural disasters along the coastal regions from tropical to temperate zones. Understanding the three-dimensional (3-D) wind fields in TCs helps in assimilating their dynamics and predicting their evolution. Unfortunately, up to now, there is no spaceborne weather radar with Doppler capability to measure the 3-D wind components in the global scale. This paper presents a novel scanning strategy for future spaceborne Doppler weather radar mission to retrieve 3-D wind fields of TCs, which has three downward-pointing (with three different fixed tilt angles) and conically scanning beams. With spaceborne Doppler detection, the radar system enables to measure the vertical motion of hydrometeors, which is important in the estimation of latent heat fluxes and in the study of energy transportation in the structure of TCs on a global scale. A novel scanning strategy is presented and optimized to construct three noncollinear radar observations. Three-dimensional wind fields are retrieved using the least-squares method. A model simulation of TCs is used to validate the proposed scanning strategy. The radar beams of the proposal are able to cover TC's full area of interest. The results demonstrate a suitable accuracy of the proposed scanning strategy on retrieving the TC's 3-D wind fields with a resolution of 10 km × 10 km × 0.25 km grid cell, showing a promising use in the future spaceborne Doppler radar.

Numerical method for wind energy analysis applied to Apulia Region, Italy

A numerical method, named WEST (Wind Energy Study of Territory), has been developed and applied to a specific geographical area in south of Italy. This method, through actual historical meteorological and geophysical data of a territory, allows characterizing anemometric fields and, therefore, potential available wind power. WEST has been developed in such a way to be effective in both studies of large area and siting. Particularly, this method is composed by different calculation algorithms, which altogether constitutes the numerical model, which allow obtaining useful information on the technical feasibility of installing wind turbine in an area.In this work, by means of WEST, three-dimensional wind fields of Apulia Region (Italy) have been reconstructed, obtaining the wind power density maps at several heights: 35 m, 60 m, 80 m and 100 m above ground level.

Observation and analysis of atmospheric rainfall based on the very high frequency radar

Very high frequency (VHF) radar can not only get higher resolution atmospheric three-dimensional (3D) wind fields, but also observe complex atmospheric echoes in the rainfall environment. This paper uses Chung-Li VHF Radar with five beams to observe the frontal rainfall and explore the physical process of atmospheric rainfall. The observed results indicate: 1) the height of bright band is at about 3.5 km with the thickness about 0.5 km and is lower about 0.5 km than the zero isotherm observed by the radiosonde. 2) When the strong updraft exists, the rainfall echoes will weaken and the bright band will be indistinct; when the downdraught exists, the rainfall echoes will strengthen and the bright band will be distinct. 3) The thickness of melting layer is about 1 km, the velocity of rainfall particles in the melting layer is smaller than that below it but spectral width is the opposite. The aspect sensitivity calculated from five beams shows that the radar rainfall echoes mainly come from the anisotropic scattering below the melting layer but isotropic scattering in the melting layer.

洋上風観測を利用したカルマンモデルの乱流スケールに関する研究

Accurate prediction of the secondary moment of three-dimensional turbulent wind field is important for structure dynamic analysis, while literatures on turbulence scales for offshore wind field are limited. In this study, an offshore wind field measurement campaign is carried out by an offshore meteorological mast using ultrasonic anemometers at 40, 60 and 80m heights, from which the turbulence integral length scales used in von Karman model are evaluated. It is found that turbulence structure at these heights for offshore wind field can be expressed well by von Karman model. The length scales are evaluated by model fitting for auto-spectrum and spatial coherence. The scales for auto-spectrum showed similar values with the IEC design code for longitudinal, lateral and vertical component. Spatial length scales in vertical direction show similar value with the model provided in ESDU considering surface roughness, but were larger compared to previous measurements in suburban area for longitudinal and lateral components. Spatial length scale in vertical direction for vertical component shows similar value with the previous measurement in lateral direction. Finally, a model for the turbulence length scales of three velocity components in von Karman model is proposed for offshore wind field, based on the measured results and previous studies.

Effect of motion path of downburst on wind-induced conductor swing in transmission line

In recent years, the frequency and duration of supply interruption in electric power transmission system due to flashover increase yearly in China. Flashover is usually associated with inadequate electric clearance and often takes place in extreme weathers, such as downbursts, typhoons and hurricanes. The present study focuses on the wind-induced oscillation of conductor during the process when a downburst is passing by or across a specified transmission line. Based on a revised analytical model recently developed for stationary downburst, transient three-dimensional wind fields of moving downbursts are successfully simulated. In the simulations, the downbursts travel along various motion paths according to the certain initial locations and directions of motion assumed in advance. Then, an eight-span section, extracted from a practical 500 kV ultra-high-voltage transmission line, is chosen. After performing a non-linear transient analysis, the transient displacements of the conductors could be obtained. Also, an extensive study on suspension insulator strings' rotation angles is conducted, and the electric clearances at different strings could be compared directly. The results show that both the variation trends of the transient responses and the corresponding peak values vary seriously with the motion paths of downburst. Accordingly, the location of the specified string, which is in the most disadvantageous situation along the studied line section, is picked out. And a representative motion path is concluded for reference in the calculation of each string's oscillation for the precaution of wind-induced flashover under downburst.