Wind Turbulence Research Articles

LIDAR‐assisted feedforward individual pitch control of a 15 MW floating offshore wind turbine

AbstractNacelle‐mounted, forward‐facing light detection and ranging (LIDAR) technology can deliver benefits to rotor speed regulation and loading reductions of floating offshore wind turbines (FOWTs) when assisting with blade pitch control in above‐rated wind speed conditions. Large‐scale wind turbines may be subject to significant variations in structural loads due to differences in the wind profile across the rotor‐swept area. These loading fluctuations can be mitigated by individual pitch control (IPC). This paper presents a novel LIDAR‐assisted feedforward IPC approach that uses each blade's rotor azimuth position to allocate an individual pitch command from a multi‐beam LIDAR. In this study, the source code of OpenFAST wind turbine modelling software was modified to enable LIDAR simulation and LIDAR‐assisted control. The LIDAR simulation modifications were accepted by the National Renewable Energy Laboratory (NREL) and are now present within OpenFAST releases from v3.5 onwards. Simulations of a 15 MW FOWT were performed across the above‐rated wind spectrum. Under a turbulent wind field with an average wind speed of 17 ms−1, the LIDAR‐assisted feedforward IPC delivered up to 54% reductions in the root mean squared errors and standard deviations of key FOWT parameters. Feedforward IPC delivered enhancements of up to 12% over feedforward collective pitch control, relative to the baseline feedback controller. The reductions to the standard deviation and range of the rotor speed may enable structural optimization of the tower, while the reductions in the variations of the loadings present an opportunity for reduced fatigue damage on turbine components and, consequently, a reduction in maintenance expenditure.

Scaling law of the second-order structure function over the entire sandstorm process

This study reveals the competitive evolutionary process of the main driving factors in the early, middle and late stages of sandstorms, as shear turbulence becomes dominant and is then suppressed by enhanced thermal stability, based on quadrant analysis of the sand-laden turbulent wind field acquired from field observations over the entire sandstorm process. Moreover, the self-organized state of multiscale structures in the energy-containing region of the sand-laden turbulence is found to change significantly as the sandstorm develops. The logarithmic scaling law that governs the cumulative turbulent kinetic energy for the non-stationary flow in the early and late stages of the sandstorm is different from the existing theoretical formula. The corresponding rate of increase in the cumulative kinetic energy with increasing scale is much higher in these stages than in the middle stage of the sandstorm with steady flow. The change in self-organized state of turbulence is responsible for the flow acceleration and the thermal superimposed effect, rather than the addition of sand particles.

Coherence of Elsässer Variables in the slow solar wind from 0.1 au to 0.3 au

The highly Alfvénic fluctuations (AF) and magnetic-velocity alignment structures (MVAS) are two distinguished components in the near-Sun slow solar wind observed by Parker Solar Probe. The amplitudes of the Elsässer Variables z± of AF and MVAS show distinct features. However, how these fluctuations contribute to the slow solar wind turbulence remains unknown. Here we investigate the coherence between z+ and z− for the first time using the Parker Solar Probe measurements with a high resolution 0.8738 s in the slow solar wind from 0.1–0.3 au. We find that the coherence spectra of z+ and z− in the perpendicular directions for MVAS are remarkable higher than that for AF, in particular at large scale. There exists a break around 10 di (di is the ion inertial length) where the coherence decreases to a lower level for MVAS. A bump around 10 di appears on the coherence spectra of all three components for AF. The coherence of z+ and z− may relate to the possible nonlinear interactions reflected by the time series, the power spectra, and the self-correlation functions. These results help to understand the roles of AF and MVAS in the slow solar wind turbulence.

An efficient power control strategy for active mitigation of blade in‐plane fatigue loading in PMSG‐based wind turbines

AbstractThis paper assesses the dynamic performance of permanent magnet synchronous generator‐based wind turbine (WT) regarding the blade in‐plane fatigue loads once the WT is controlled in power control mode. Blade in‐plane oscillations, associated with the poorly blade in‐plane modes, can be excited by turbulent winds or grid disturbances that may lead to damage of the blades and reduce the drive‐train reliability. To overcome this drawback, at first, a model with three degrees of freedom is extracted for the drive‐train system, and then, an active mitigation approach is proposed to mitigate the blade in‐plane oscillations. The proposed method can effectively suppress the blade in‐plane vibrations by adding a supplementary term into the power control loop that is proportional to the speed difference between the blade and generator. The speed difference between the blade and generator is obtained by estimation of the blade‐hub and hub‐generator shaft torsional torques. Next, the performance of the proposed active mitigation approach is examined by the modal and frequency response analyses and time‐domain simulations. Finally, it is shown that the proposed approach has superior performance over the conventional approaches based on the simplified drive‐train model and crossing the measured generator speed through a band‐pass filter.

Impact of atmospheric rivers on Arctic sea ice variations

Abstract. Arctic sea ice has been declining rapidly in recent decades. We investigate how the poleward transport of moisture and heat from lower latitudes through atmospheric rivers (ARs) influences Arctic sea ice variations. We use hourly ERA5 (fifth-generation European Reanalysis) data for 1981–2020 at 0.25∘ × 0.25∘ resolution to examine the meteorological conditions and sea ice changes associated with ARs in the Arctic. In the years 2012 and 2020, which had an extremely low summer Arctic sea ice extent, we show that the individual AR events associated with large cyclones initiate a rapid sea ice decrease through turbulent heat fluxes and winds. We carry out further statistical analysis of the meteorological conditions and sea ice variations for 1981–2020 over the entire Arctic Ocean. We find that on weather timescales the atmospheric moisture content anticorrelates significantly with the sea ice concentration tendency almost everywhere in the Arctic Ocean, while the dynamic sea ice motion driven by northward winds further reduces the sea ice concentration.

Dynamic reliability analysis of Aerial Building Machine under extreme wind loads using improved QBDC-based active learning

Aerial building machine (ABM) is a new comprehensive construction equipment used for the construction of high-rise buildings, and the research of its wind-induced response is essential for structural safety. However, the traditional reliability estimation for complex structures is generally computationally expensive. This study proposes a novel and time-saving active learning (AL) approach to predict the structural time-variant response and calculate the reliability under extreme wind loads based on improved Query-by-Dropout-Committee (QBDC), Deep Learning (DL) and Probability Density Evolution Method (PDEM). To establish an effective training set, the load sample pool from the turbulent wind field is constructed by the number theory method (NTM). Then a DL surrogate model, aimed to simulate the excitation-response relationship of the structure, is well-trained from data calculated by the Finite Element Method (FEM) under the workflow of the improved QBDC-based AL approach. Lastly, the structural responses predicted by the surrogate model are used to solve the Generalized Density Evolution Equation (GDEE) to obtain the Probability Density Function (PDF) of the structural response. The dynamic reliability can be gained using absorbing boundary condition. To demonstrate the feasibility of the proposed approach, an ABM in China is taken as a case study. It is found that (1) The external trusses of the platform are weak positions under the horizontal wind loads. It is suggested to append the longitudinal (windward direction) trusses to reduce the local stress and deformation. (2) Under turbulent wind loads with the average speed of 40 m/s, the maximum structural response of the ABM will exceed the threshold value and the reliability is 0.932. (3) The reliability calculation error derived by the proposed approach and the traditional PDEM is within 0.5 % in this study, while the computational efficiency of the AL approach is 77.08 % higher than that of the traditional PDEM. The novelty lies in the proposed active learning approach that can easily obtain the stochastic response and dynamic reliability of the ABM, where the analysis workflow not only has a low computational cost but also maintains a high calculation accuracy.

A numerical investigation of momentum flux and kinetic energy transfers between turbulent wind and propagating waves

This paper focuses on simulating turbulent flow over propagating waves by solving the full Navier–Stokes equations in a moving frame. A careful comparison of flow statistics with previous experimental and numerical results demonstrates, to some extent, the rationality of simplifying wind waves as turbulent flow over moving wave boundaries. The phase-averaging method is then applied to investigate the momentum and energy transfers between turbulent wind and waves propagating at slow, intermediate and fast speeds. The results suggest that the dominant mechanism for producing Reynolds shear stress (RSS) and turbulent kinetic energy (TKE) is related to the wave age. Slow waves produce RSS and TKE similar to a two-dimensional shear turbulence. However, a fast wave enhances the streamwise Reynolds normal stress, the windward side's negative RSS and the gradient of both streamwise and vertical velocities, leading to additional RSS and TKE productions that can be ignored under the slow wave regimes. A strengthening wave–turbulence exchange is also found for fast waves. The intermediate wave can be regarded as a transitional condition determining this change.

Numerical investigation of wind turbine wake characteristics using a coupled CFD-CSD method considering blade and tower flexibility

With the increase in wind turbine sizes, careful investigation into wind turbine wake effect is crucial for operational safety. This study proposes a two-way fluid-structure interaction (FSI) model combining large eddy simulation (LES) and computational structural dynamics (CSD) to investigate wind turbine wake characteristics. Examining the effect of blade and tower flexibility and inflow conditions, the study reveals negligible influence of blade and tower flexibility on mean velocity deficit under both inflow conditions. However, they significantly impact turbulence intensity under uniform inflow condition. The tower motion produces a maximum increase of approximately 45% while the blade flap-wise motion has the second-largest impact, increasing the maximum turbulence intensity by approximately 33% when compared with the fully rigid case. Additionally, the study quantitatively examines wake vortex inclination based on the inclination angle of the second-circle wake vortex structure. Finally, the study concludes that the streamline near the blade tip follows the blade surface, while the flow separation occurs near the blade root, generating two vortices on the suction side. As the tower motion is considered, the larger vortex exhibits alternate vortex shedding while the smaller vortex remains stable in both uniform and turbulent winds.

Aerodynamic and aeroelastic response of wind barrier over trapezoidal box girder bridge under turbulence wind

Aerodynamic and aeroelastic response of wind barrier over trapezoidal box girder bridge under turbulence wind

Efeitos de interferência nas cargas do vento prescritos por códigos e normas: eles podem ser generalizados?

Abstract Understanding and quantifying the effects of aerodynamic interference is fundamental to designing safe and efficient buildings; however, there is a complexity in this phenomenon that characterizes it as the greatest challenge of wind engineering and thus limits improving design guidelines in a normative way. Therefore, this study investigated the impacts of building interference on wind-induced loads on a tall building through wind tunnel tests conducted using the synchronous pressure measurement technique. This impact was quantified using the interference factors (IFs) on the along-wind, across-wind and torsional force coefficients, which were mapped considering different wind angles, relative positions and number of buildings, in addition to the terrain roughness. It was observed that the protection effect in a static analysis is a dominant phenomenon in most studied scenarios when there is wind interference. The largest extension of the amplification zones occurred in scenarios in which the wind blew against the smallest facade of the analyzed building and the largest facade of the interfering building, where the coefficient of torsional moment was more sensitive to changes in wind turbulence.

Identifying kinetic scale magnetic discontinuity structures in turbulent solar wind

Identifying kinetic scale magnetic discontinuity structures in turbulent solar wind

Investigation of wind veer characteristics on complex terrain using ground-based lidar

The wind direction shift with height significantly influences wind turbine performance, particularly in relation to terrain conditions. In this work, wind conditions at 12 measurement heights ranging from 40 m to 200 m using a ground lidar, Windcube V2, installed on a 16 m tall building were analysed to examine the characteristics of wind veer angles in complex terrain. The measurement campaign was carried out from January 1st to December 31st, 2022, in the southeastern part of South Korea. The terrain complexity around the ground lidar system was evaluated using the ruggedness index (RIX), whose result was 14.06 percent corresponding to complex terrain. The ground lidar measurements were compared with mesoscale data, EMD-WRF South Korea, for the data accuracy check. Wind veer frequencies and wind roses were derived to identify directional shifts with height. Furthermore, diurnal, monthly, and seasonal variations of wind veer characteristics were analysed. Wind shear exponent factor (WSE) and turbulence kinetic energy (TKE) were calculated, and wind veer profiles were constructed based on these parameters. The relative errors of wind speeds were analysed for rotor equivalent wind speed (REWS) and hub height wind speed (HHWS), with REWS with wind veer correction, REWSveer, as a reference. Additionally, atmospheric stability conditions were classified using WSE and TKE, and the vertical changes in wind veering were analysed according to the stability conditions. The findings reveal lower wind speeds exhibited larger wind veer values and fluctuations. The relative errors for the REWS and the HHWS were 0.04 % and 0.20 % on average, respectively. The study demonstrates that terrain conditions significantly impacted wind veer angles at heights below 100 m, whereas the influence diminished with increasing height above 100 m. The results could be helpful for wind farm developers to make decisions on the siting as well as the hub height of wind turbines on complex terrain

Characteristics evaluation of constructed low turbulence wind tunnel

Characteristics evaluation of constructed low turbulence wind tunnel

Solar Plasma Structures and Solar Wind Plasma Turbulences in Relation with Geomagnetic Disturbances during Decline Phase of Solar Cycle 24 and Rising Phase of Solar Cycle 25

We have studied the effect of solar structures and turbulences in solar wind plasma on the Earth's magnetosphere during the decline phase of solar cycle 24 and the rising phase of solar cycle 25. Most CMEs are geoeffective, cause geomagnetic storms, and are associated with C-class and M-class solar flares (S.F.s). It is also observed that these geomagnetic storms are associated with disturbances in solar wind plasma parameters. We have determined a large positive correlation with a correlation coefficient of 0.68, 0.58, 0.65, and 0.63 between the magnitude of the extensive geomagnetic storms and the peak value of IMF Btotal, the magnitude of IMF Btotal, the peak value of disturbances in the southward component of interplanetary magnetic fields (IMF Bz), and magnitude of disturbances in the southward component of interplanetary magnetic fields (IMF Bz). The correlation coefficient of 0.61 is higher between the magnitude of Dst and the magnitude of SWPT, as compared with the magnitude of flow pressure (0.39). From the present work, we have concluded that solar plasma structures and solar wind turbulences are mainly responsible for generating extensive geomagnetic storms.

Study on the influence of cross-section shape on the characteristics of wind flow field in heavy-daty railway tunnel

In order to reduce the coal dust pollution when the heavy train enters the tunnel and to ensure the safety of railroad operation, this paper adopts numerical simulation to study the characteristics of the wind flow field of the heavy train passing through different shapes of tunnels. The results show that the shape of the tunnel section has a significant effect on the piston wind characteristics of the train entering the tunnel. When the train passes through the tunnel, the value of the wind pressure and the gradient of the pressure on the surface of the carriages increase from horseshoe shape, high wall shape and high arch shape. The vortex structure generated at the entrance of the horseshoe tunnel is the smallest and the flow field is more stable, and the wind turbulence shows significant weakening effect; when the rear end of the car enters the tunnel, the range of the influence of the piston winds outside the tunnel is in order of smallest to largest for the horseshoe, high wall, and high arch tunnels; in the wake region, the central region of the strong vorticity zone in the horseshoe tunnel is more continuous, reducing the instability of the airflow in the tunnel. The results of this study are of great significance in understanding the characteristics of the wind flow field and the effect on dust generation when heavy trains pass through the tunnel.

Dynamic responses analysis of crane-blade coupling system for the single blade installation of offshore wind turbine considering the wind effect

The single blade installation method for large-scale offshore wind turbine has the advantage of reduced deck and crane requirements on the installation vessel. Accurately simulating the coupled dynamic responses of the system throughout the entire hoisting process is crucial to avoid spatial interference with surrounding structures. Additionally, the aerodynamic loads, particularly the turbulent wind with spatiotemporal non-uniformity, further aggravate the uncertainty of the dynamic responses. Therefore, a numerical model capable of comprehensive analysis of mechanical-hydrodynamic-aerodynamic-control is urgently needed. However, it is challenging for the commercial software to achieve the coupling analysis. In this paper, the hoisting process is investigated by jack-up installation vessel, so the influence of wave loads on the structure is not considered. The aerodynamic loads are firstly calculated by the blade element theory, and then the numerical model is established by the Lagrangian method, finally the analysis program is developed in MATLAB. The accuracy of the program is verified by code-to-code, and the interaction between the ship-mounted crane and aerodynamic loads during the hoisting process are analyzed. The results show that the aerodynamic loads should be considered during the hoisting of the blade, and the established program could determine the trajectory of the blade inputting the sea state, which can avoid the possible collisions with the surrounding structures.

A computational framework for the co-optimization of platform hydrodynamic and passive structural control of floating offshore wind turbines

Floating offshore wind turbines extract rich and stable wind energy in the deep sea. However, they face severe sea conditions and high maintenance costs, and a promising method is needed to generate a high-performing, reliable, and robust design. Traditional sequential methods overlook the coupling between sub-systems and may miss the global optimum. The control co-design method, in contrast, focuses on the integrated optimization of the whole system. However, implementing co-simulation and co-optimization for co-design is challenging. In this study, a control co-design framework is developed and validated to couple the platform hydrodynamics with multi-physical wind turbines for integrated simulations and optimization. Based on this framework, the floating platform and tuned mass damper are co-optimized by establishing an efficient Kriging-enhanced Genetic algorithm. A case study is conducted using a 10 MW floating offshore wind turbine for demonstration. The platform shape and tuned mass dampers are parameterized by five and three design variables, respectively. To minimize platform mass, two formulations are proposed, that is, multi- and single-objective, for scenarios with and without consideration of structural loads. These formulas are solved under pre-defined turbulent wind and irregular wave conditions. Compared to the baseline model, the optimal design significantly reduces platform mass, enhancing both power generation and platform motion stability. After involving structural load in optimization, the optimal platform mass, energy production, and platform motion stability are degraded. These findings demonstrate the effectiveness of the co-design framework in optimizing platform geometry and passive structural control.

Research on the Anti-Swing Control Methods of Dual-Arm Wheeled Inspection Robots for High-Voltage Transmission Lines

This paper presents an anti-swing control method to prevent situations where inspection robots detach and fall off transmission lines during obstacle crossing due to excessive swing angles caused by the rotation of the robot around the transmission line. Firstly, an obstacle-crossing model for the inspection robot was constructed and the causes of robot swinging phenomena were analyzed, in addition to their impact on obstacle crossing stability. By combining this with the obstacle-crossing model, a moment balance equation was established for the inspection robot. This equation can be used to solve mapping relationships between body offset and the tilt angle of transmission line gripping arms. We propose an anti-swing control strategy by adjusting the angle of the transmission line gripping arm’s pitching joint to make the body offset approach zero, and by utilizing the advantages of fuzzy logic in the fuzzy PID algorithm compared with the traditional PID algorithm, it can adaptively avoid the occurrence of robot swinging phenomena. The experimental results of obstacle-crossing experiments under no wind and wind turbulence conditions indicated that the proposed anti-swing control method in this study can effectively keep the body offset to within 3 mm. Compared with the methods of not using anti-swing control and using traditional PID anti-swing control, in the absence of wind effects, the peak values of body offset were reduced by 96.53% and 18.85%, respectively. Under the influence of wind turbulence, the peak values of body offset were reduced by 97.02% and 27.12%, respectively. The effectiveness of the anti-swing control method proposed in this paper has thus been verified.

Prediction and Early Warning of Extreme Winds for High-Speed Railway Bridge Construction Using Machine-Learning Methods

Measuring the impact of extreme winds is important in high-speed railway bridge construction to avoid the risk of engineering accidents. This study presents an early-warning framework for high-speed railway (HSR) bridge construction under extreme wind conditions, using a long-span continuous beam bridge constructed in a typhoon-prone area as a case study. Specifically, on-site wind environment measurements during a typhoon are utilized, and parameters such as fluctuating wind turbulence intensity, gust factor, turbulence integral scale, and power spectral density are employed to characterize the wind environment. Multi-step prediction of gust wind speed during the bridge construction is performed using the hybrid Back Propagation-Genetic Algorithm (BP-GA). Hierarchical warnings and control actions are proposed and implemented based on the prediction results. The analysis results of wind parameters revealed a discrepancy between the measured and specified typhoon turbulence intensities, with the windward turbulence intensity being lower than specified. The longitudinal average gust factor exceeded the transverse value. The prediction curve based on the BP-GA algorithm closely resembles the actual curve, meeting accuracy requirements. Notably, the one-step prediction provided the most accurate results. Based on the predicted wind speed trend for the upcoming half-hour, appropriate hierarchical warnings and control measures were conducted.

Flight Dynamic Characteristics of Wide-Body Aircraft with Wind Gust and Turbulence

In this research, a wide-body aircraft was analyzed with critical monitoring of its states, a function of several control inputs (wind gust, turbulence, and microburst). The aerodynamic and stability coefficients of a Boeing 747-200 were obtained from previously published works and 6- DOF equations were formulated. Simulations were conducted for various control inputs to determine the aircraft’s free response, as well as the forced response. In order to understand the nature of the atmosphere, three different models were incorporated, including (i) the Dryden Model, (ii) wind gust, and (iii) microburst. The aircraft was found to be stable in the longitudinal and lateral flight modes, with trim conditions agreeing with published data. For a vertical wind gust of −10 ft/s, the AoA and pitch rate were observed to oscillate sinusoidally and became stable with new trim conditions. These states were found to regain trim conditions once the gust was removed. In the case of 3D gust, it was found that the longitudinal modes achieved a new trim condition through Phugoid oscillations, whereas the lateral modes underwent short-period oscillations. For the case of turbulence, random fluctuations were observed for trim conditions with no unstable behavior. When considering the microburst case, it was found that the aircraft initially gained altitude in the region of the headwind; this was followed by a sharp descent under the influence of a vertical velocity component.