Turbulent Wind Loading Research Articles

Fragility curves of a slender structure fitted with tuned mass dampers subjected to turbulent wind and seismic loading

In the context of structural performance assessment, several studies have employed fragility curves and surfaces to evaluate the damage probability for predefined intensity levels of a single or multiple hazards. Further, some of these studies have considered the use of tuned mass dampers (TMDs) to reduce the response of structures under wind or seismic loading. In this work, fragility curves and surfaces of a slender structure fitted with TMDs subjected to turbulent wind and seismic loading alone and simultaneously are developed. For the numerical analyses, simulated records for wind and earthquake ground motion are considered. For the development of fragility curves and surfaces, three damage states that include local and global behavior of the structure are considered. The analysis results indicate that, for the structure considered, higher probability of damage is found from wind action than from earthquake, and that an important reliability enhancement is achieved with the use of TMDs.

Wavelet LQR based gain scheduling for power regulation and vibration control of floating horizontal axis wind turbine with double-pitched rotor

This paper introduces a wavelet-based linear quadratic regulator (LQR) control strategy for double-pitched rotor systems of an offshore horizontal axis wind turbines. A comprehensive aero-servo-elastic model incorporating bending-torsion coupling is developed to assess the performance of the proposed controller under combined turbulent wind and wave loading. The weight matrices of the classical LQR algorithm are optimized using a nonlinear optimization scheme. Additionally, frequency-dependent gain scheduling is proposed using wavelet transform where the analytic Morse wavelet serves as the basis function. The resulting LQR algorithm operates in the time-frequency domain and solves scale-dependent Algebraic Riccati equations to determine optimal gains. Numerical simulations demonstrate the superior performance of the proposed gain scheduling compared to the classical LQR approach. The effectiveness of the algorithm is evaluated across various flow conditions and wind-wave misalignment, with benchmark results used for performance comparison.

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.

Investigation of the dynamic response of a floating wind-aquaculture platform under the combined actions of wind, waves and current

Floating wind-aquaculture platforms are drawing increasing attention from the academic and engineering communities due to their potential to fully exploit and utilize marine space and its resources. However, these platforms integrate both the hydrodynamics and aerodynamics of floating wind turbines and aquaculture cages, making their mechanical properties more complex. This study aims to evaluate the effects of three different hydrodynamic and aerodynamic damping components on and the contribution of the stochastic environmental loads to the dynamic response of a floating wind-aquaculture platform. A coupled hydro-aero-servo method is established. Decay and forced oscillation tests of the platform in still water are firstly numerically performed, followed by simulation of the dynamic behavior under different combinations of environmental loads, including the fluctuating wind load of the blades, stochastic wave excitation forces on the floating body and viscous force of the aquaculture cage system. The aerodynamic damping of the wind turbine and the hydrodynamic damping of the floating body are dominant in low- and wave-frequency range, respectively. Regarding the environmental load components, the second-order wave force and the turbulent wind load are dominant in the surge direction in the low-frequency range. The dynamic response of the platform in the wave-frequency range is mainly induced by the first-order wave force. Fish net can suppress the low-frequency motion but has almost no influence on the wave-frequency motion.

Dynamic Response Analysis of Wind Turbine Structure to Turbulent Wind Load: Comparative Assessment in Time and Frequency Domains

This study investigates wind turbine structural dynamics using stochastic analysis and computational methods in both the time and frequency domains. Simulations and experiments are utilized to evaluate the dynamic response of a wind turbine structure to turbulent wind loads, with the aim of validating the results based on real wind farm conditions. Two approaches are employed to analyze the dynamic responses: the frequency domain modal analysis approach, which incorporates von Kármán spectra to represent the turbulent wind loads, and the time domain Monte Carlo simulation and Newmark methods, which generate wind loads and determine dynamic responses, respectively. The results indicate that, for a larger number of samples, both methods consistently yield simulated turbulent wind loads, dynamic responses and peak frequencies. These findings are further validated through experimental data. However, when dealing with a smaller number of samples, the time domain analysis produces distorted results, necessitating a larger number of samples to achieve accurate findings, while the frequency domain method maintains accuracy. Therefore, the accurate analysis of wind turbine structural dynamics can be achieved using simulations in both the time and frequency domains, considering the importance of the number of samples when choosing between time domain and frequency domain analyses. Taking these considerations into account allows for a more comprehensive and robust analysis, ultimately leading to more effective outcomes.

Active hybrid energy storage management in a wind-dominated standalone system with robust fractional-order controller optimized by Gases Brownian Motion Optimization Algorithm

Accessibility to sustainable and reliable electrical energy for remote area power supply (RAPS) systems under high penetration levels of wind energy requires adopting appropriate technologies and controllers. In recent years, energy storage has gained significant attention for smoothing inherent voltage and power fluctuations of standalone systems. This paper presents a filtration-based fractional-order PI (FOPI) controller optimized by Gases Brownian Motion Optimization (GBMO) algorithm to manage an active battery-supercapacitor hybrid energy storage system (HESS) in a wind-dominated RAPS system. The GBMO algorithm has a high accuracy and convergence rate among optimization algorithms introduced in recent years. Moreover, a fuzzy logic controller (FLC) guarantees the wind turbine generator's maximum power point tracking (MPPT) at any wind condition while mitigating its fluctuating torque. The proposed RAPS system uses the advantages of the FOPI controller, the GBMO optimization algorithm, the FLC-based MPPT algorithm, and a high-pass filter to manage precise coordination between different components of the RAPS system. The high-pass filter decouples high and low-frequency voltage oscillations to modify the HESS performance and relieve battery stress, thereby extending its lifespan. The proposed controller's performance and robustness are verified in comparison with an optimal PI controller based on GBMO under turbulent wind speed and load step changes in a detailed model of the system. The results demonstrate the superiority of the optimal FOPI controller over the optimal PI controller.

An individual pitch control method for floating offshore wind turbine

As the vast deep-water wind resource represents a potential development of a superior resource in comparison to the coast and land, the floating offshore wind turbine (FOWT) represents a viable solution for increasing renewable energy generation. However, above the rated wind speed region, the influence of turbulent wind loads is more severe on the floating offshore wind turbine. Thus, the control system’s primary objective should be to minimize fatigue loads and irregular power output swings to achieve smooth power output. This paper proposes a feedback method of individual pitch control for FOWT that, by utilizing a feedback control strategy, effectively reduces asymmetric aerodynamic loads and platform motion. The effectiveness of the method is verified through simulation verification.

Aerodynamic Behavior and Stability of the Tall and Slender Brasilia Telecom Tower

The 192 m tall Brasilia Telecom Tower was designed in 1958 as part of the infrastructure of the new capital of Brazil. During its more than 55 years in service, a great number of accessories and antennas have been attached to the upper third of its height altering the lumped mass distribution and the wind loading on the tower structure. To evaluate the effect of such alterations, a comprehensive study of the aerodynamic behavior and structural stability was performed with the aid of a 3D computational model of the complete tower structure and short-term dynamic monitoring. This procedure allowed the structural model to be validated through the correlation between theoretical and experimental vibration frequencies and aerodynamic displacement amplitudes. The computational model was then used to obtain time-domain responses of the tower structure under the action of turbulent wind loading for various wind directions. It was found that the existing antennas and their supports caused a considerable increase in the aerodynamic forces and consequent response amplitudes. Two alternative solutions were then considered: structural reinforcement of elements and the installation of dynamic control devices. Both alternatives are described briefly, and their efficiency is discussed in light of the numerical results obtained.

The COTUR project: remote sensing of offshore turbulence for wind energy application

Abstract. The paper presents the measurement strategy and data set collected during the COTUR (COherence of TURbulence with lidars) campaign. This field experiment took place from February 2019 to April 2020 on the southwestern coast of Norway. The coherence quantifies the spatial correlation of eddies and is little known in the marine atmospheric boundary layer. The study was motivated by the need to better characterize the lateral coherence, which partly governs the dynamic wind load on multi-megawatt offshore wind turbines. During the COTUR campaign, the coherence was studied using land-based remote sensing technology. The instrument setup consisted of three long-range scanning Doppler wind lidars, one Doppler wind lidar profiler and one passive microwave radiometer. Both the WindScanner software and LidarPlanner software were used jointly to simultaneously orient the three scanner heads into the mean wind direction, which was provided by the lidar wind profiler. The radiometer instrument complemented these measurements by providing temperature and humidity profiles in the atmospheric boundary layer. The scanning beams were pointed slightly upwards to record turbulence characteristics both within and above the surface layer, providing further insight on the applicability of surface-layer scaling to model the turbulent wind load on offshore wind turbines. The preliminary results show limited variations of the lateral coherence with the scanning distance. A slight increase in the identified Davenport decay coefficient with the height is partly due to the limited pointing accuracy of the instruments. These results underline the importance of achieving pointing errors under 0.1∘ to study properly the lateral coherence of turbulence at scanning distances of several kilometres.

CFD and Mapping-Induced FSI Analyses of Soundproof Tunnels with Un-symmetric Shapes under a Turbulent Wind Load

This study investigates a turbulent wind-induced dynamic behavior of a soundproof tunnel structure with un-symmetric shape. The combined computational fluid dynamics (CFD) and fluid-structure interaction (FSI) simulations proposed in this study may allow us not only to investigate realistic wind effects but also to provide various parameters for the structural design. The CFD and FSI simulation were verified in comparisons with a full-scale experiment of soundproof frames. Subsequent simulation results present that displacements, stresses, and shear forces induced from the FSI analysis are heavily dependent on curved shapes and the wind direction of the soundproof tunnel. From parametric results, the technique proposed in this study is computationally efficient in characterizing behaviors for complex structures such as soundproof tunnels with un-symmetric shapes.

Dynamic characteristics analysis of planetary gear system with internal and external excitation under turbulent wind load.

According to the working characteristics of a 1.5 MW wind turbine planetary gear system under complex and random wind load, a two-parameter Weibull distribution model is used to describe the distribution of random wind speed, and the time-varying load caused by random wind speed is obtained. The nonlinear dynamic model of planetary gear transmission system is established by using the lumped parameter method, and the relative relations among various components are derived by using Lagrange method. Then, the relative relationship between the components is solved by Runge Kutta method. Considering the influence of random load and stiffness ratio on the planetary gear transmission system, the nonlinear dynamic response of cyclic load and random wind load on the transmission system is analyzed. The analysis results show that the variation of the stiffness ratio makes the planetary gear have abundant nonlinear dynamics behavior and the planetary gear can get rid of chaos and enter into stable periodic motion by changing the stiffness ratio properly on the premise of ensuring transmission efficiency. For the variable pitch wind turbine, the random change of external load increases the instability of the system.

A Smart Tower Crane to Mitigate Turbulent Wind Loads

Tower cranes have, in general, low structural damping, leading to challenges with respect to vibrations induced by natural hazards. Crane failures due to wind excitations are very common around the world. In the present research work, a smart tower crane equipped with pairs of collocated sensors and actuators is proposed to mitigate turbulent wind. A three-dimensional finite element model of the crane is created using MATLAB®/Structural Dynamics Toolbox. Modal analysis is performed to calculate natural frequencies and corresponding mode shapes. Dynamic analysis of the crane is carried out under turbulent wind excitation. A decentralized active vibration control method is then used to prevent collapse of the crane. Active damping is added to the tower crane using pairs of force actuators–displacement sensors collocated on selected elements. A robust control strategy based on decentralized direct velocity feedback is implemented. The vibrations of the tower crane in all directions are significantly damped. It is concluded that the proposed smart tower crane model is highly efficient in mitigating the turbulent wind loads.

Numerical Simulation of Buffeting Response of Cable-stayed Truss Bridge with Unconventional Load in Port

Zhang, X.-T.; Chen, X.-J.; Wang, Q.; Li, P., and Zhou, H.-M., 2019. Numerical simulation of buffeting response of cable-stayed truss bridge with unconventional load in port. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 275–279. Coconut Creek (Florida), ISSN 0749-0208.Wind and waves seriously threaten the safety of structures in coastal ports. In this paper, the long-span cable-stayed truss structure in port for ore transportation along the coast is taken as the analysis object, with the static three-point force coefficient which obtained based on numerical wind tunnel simulation, the buffeting response of structure induced by turbulent wind load is studied by time-domain analysis method. The results show that the amplitude of buffeting response induced by turbulent wind load is larger than that of static wind load and it is also found that the increase of the main girder retaining wall and the operation load have great influence on the buffeting response of the structure. The research results can provide a strong theoretical basis for the design of the project and similar projects.

A fully coupled frequency domain model for floating offshore wind turbines

This paper presents a new frequency domain modeling approach for floating offshore wind turbines with coupled wind turbine, floating platform, and mooring system sub-models. The sub-models are generated using the validated numerical tools FAST and WAMIT to obtain the frequency domain aerodynamic and hydrodynamic characteristics, respectively, for any given design candidate. The turbulent wind and irregular wave loads are incorporated in the frequency domain model using wind and wave power spectral density functions, the JONSWAP and Kaimal spectra, respectively. To validate the proposed 6 DOF frequency domain framework across standard operational environmental conditions, predicted system responses of a 5 MW NREL offshore wind turbine with three classes of reference platforms including the OC3-Hywind, the MIT/NREL TLP, and the OC4-DeepCwind semisubmersible were compared to the outputs of 6 DOF and 22 DOF FAST time domain simulations. The comparison over an aggregate of eleven environmental conditions focused on differences in predicted platform rigid body motions and structural considerations including platform surge, roll, and pitch, and rotor thrust, total blade root and tower base bending moments/fatigue loads, fairlead and anchor tensions/fatigue loads. In terms of platform motions, the worst match of frequency and time domain model predictions was seen for the OC4-DeepCwind semisubmersible with errors of 13.2% in peak displacement values. The frequency domain model predictions of rotor thrust, blade root and tower base bending moments demonstrated the largest error in the case of the OC3-Hywind spar buoy with the peak loads differing by up to 12.8%. Errors in the predictions of maximum fairlead and anchor tensions were less than 11.5% with maximum error occurring for the MIT/NREL TLP. In terms of fatigue load comparison, the blade root and tower base fatigue load predictions showed less than 9.8% errors for all the reference platforms. Comparison of the fairlead and anchor fatigue loads showed that errors were less than 13.8% with the largest error seen for the OC3-Hywind spar buoy platform. Overall, the frequency domain model provides reliable means for assessing platforms dynamics at the conceptual stage of the design process.

Failure analysis of a lattice transmission tower collapse due to the super typhoon Rammasun in July 2014 in Hainan Province, China

The failure mechanisms of lattice transmission towers under the extreme wind conditions of typhoons are not well known and such knowledge is important for the improvement of overhead transmission line (OHL) design and to ensure the safe operation of transmission lines in typhoon-prone areas. This paper presents a case study on failure analysis of 13 collapsed lattice transmission towers in a110 kV transmission line during the super typhoon Rammasun that occurred in July 2014 in Hainan Province of China. A systematic computational procedure was developed to conduct the failure analysis with particular focus on modeling the fluctuating turbulent wind loads combined with the heavy rain loads. The results show that the failure mode and location obtained from the dynamic analysis are in good agreement with the post-event field observations. The collapse of the suspension lattice transmission towers was triggered by the buckling of the main leg members in the third panel from the ground level due to the extreme high axial stresses. Key design suggestions like improving the design wind speed and adopting an equal-strength beam approach are proposed to reduce the risk of lattice transmission tower failure and ensure continued serviceability and safe operations under the typhoon-wind conditions.

Methodology to Develop Fragility Curves of Glass Façades Under Wind-Induced Pressure

High wind speeds produced by hurricanes or synoptic winds can cause considerable damage and the failure of structural and nonstructural elements. The use of glass facades in buildings has become very popular; in Mexico, a large number of buildings along the coast are designed with glass facades. Glass facades provide light, temperature control, and an esthetic view; however, this type of glass system is particularly vulnerable to high wind-induced pressures. A methodology to determine the fragility curves of glass facades under turbulent wind loading is proposed. This methodology could be used to select the appropriate glass thickness of a facade. The procedure employs an autoregressive and moving average model to simulate the wind field and Monte Carlo techniques to simulate the glass resistance of the windows. The methodology to construct the fragility curves is illustrated with a numerical example of a glass facade of a 96-m tall building. Three cases of glass resistance associated with coefficients of variation equal to 0, 10, and 20% were considered. The results of the numerical example show that the uncertainty in the glass resistance plays an important role in the development of the fragility curves of the glass facades for high mean wind speeds between 38 and 67 m/s at a height of 10 m.

Stochastic response reduction on offshore wind turbines due to flaps including soil effects

This work attempts to investigate the load mitigation effects on foundations of NREL 5-MW offshore wind turbine (OWT) supported on fixed structures using blade trailing edge flaps. The analysis is subjected to turbulent wind and irregular wave loads. The offshore wind turbine is simulated for five met-ocean conditions for Indian scenario, covering operational to the parked region of turbine. Sea states being stochastic, the responses are obtained using average of Monte Carlo simulations. The blade element momentum theory is used to obtain the aerodynamic loads by modelling in a multi-body framework while the hydrodynamic and geotechnical analysis are performed in a finite element framework. Soil-structure interaction is modelled using nonlinear Winkler spring model along the length of the pile. The trailing edge flaps are numerically implemented through a dynamic link library into the aerodynamic program. Loose sandy soils with uniform density is considered for analysis. The results bring out the importance of including blade trailing edge flaps in OWT studies with significant response reduction (2.1–16.0%) for designing pile foundations.

Optimal operation of fuel cell/wind turbine hybrid power system under turbulent wind and variable load

In this paper is proposed a new Extremum Seeking Control (ESC) algorithm for optimal operation of Wind Turbine (WT) under turbulent wind. In this proposal the dithers’ amplitude is WT system dependent, not constant or decreasing exponentially as in the classic ESC schemes. So, instead of one, the proposed ESC scheme has two loops: (1) the classic ESC loop controlled by the loop gain (k1) to accurately find the Maximum Power Point (MPP); (2) the anticipative ESC loop controlled by the dither gain (k2) to speed-up the localization of the current MPP under turbulent wind. The obtained results for a 100 Hz dither highlight the performance of the ESC-based MPP tracking algorithm proposed: about 99.9% tracking accuracy and a searching time less than 120 ms. This performance assures a tracking efficiency higher than 99% even for gusts of wind that may occur. The Fuel Cell is proposed as backup energy source for WT Hybrid Power System to sustain the load demand and reduce the size of the Energy Storage System (ESS), even for a high variability of the WT power. In comparison with Static Feed-Forward (sFF) strategy, a fuel economy of 5 lpm can be obtained using the ESC-based Real-Time Optimization (RTO) strategies proposed here, which means about 10% from the nominal fuel consumption.

New GPU computing algorithm for wind load uncertainty analysis on high-rise systems

In recent years, the Graphics Processing Unit (GPU) has become a competitive computing technology in comparison with the standard Central Processing Unit (CPU) technology due to reduced unit cost, energy and computing time. This paper describes the derivation and implementation of GPU-based algorithms for the analysis of wind loading uncertainty on high-rise systems, in line with the research field of probability-based wind engineering. The study begins by presenting an application of the GPU technology to basic linear algebra problems to demonstrate advantages and limitations. Subsequently, Monte-Carlo integration and synthetic generation of wind turbulence are examined. Finally, the GPU architecture is used for the dynamic analysis of three high-rise structural systems under uncertain wind loads. In the first example the fragility analysis of a single degree-of-freedom structure is illustrated. Since fragility analysis employs sampling-based Monte Carlo simulation, it is feasible to distribute the evaluation of different random parameters among different GPU threads and to compute the results in parallel. In the second case the fragility analysis is carried out on a continuum structure, i.e., a tall building, in which double integration is required to evaluate the generalized turbulent wind load and the dynamic response in the frequency domain. The third example examines the computation of the generalized coupled wind load and response on a tall building in both along-wind and cross-wind directions. It is concluded that the GPU can perform computational tasks on average 10 times faster than the CPU.

Physics-Based Method for the Removal of Spurious Resonant Frequencies in High-Frequency Force Balance Tests

AbstractThe high-frequency force balance (HFFB) test is a widely used method for estimating lateral turbulent wind loads on tall buildings in a wind tunnel. The method relies on use of a highly accurate force sensor placed at the base of the tall building model to measure base forces and overturning moments. Because the turbulent wind load excitation is broadband, it is important to adequately design the connection detail between the model and the sensor. Accurate design is needed to avoid contaminating the measurement of the lateral wind loads by the potential spurious resonant effect, which is induced by flexibility in the connection detail. This design often relies on the experience of the wind tunnel modeler. On occasion, because of the limitations of test setup and environment, the connection detail between the building model and the HFFB force sensor may not be sufficiently stiff. Consequently, resonant response caused by the flexible connection may affect the power spectral density function of the ...