Wind Load Variation Research Articles

Study of Wind Load Influencing Factors of Flexibly Supported Photovoltaic Panels

Flexible photovoltaic (PV) support structures are limited by the structural system, their tilt angle is generally small, and the effect of various factors on the wind load of flexibly supported PV panels remains unclear. In order to investigate the shape coefficients of the flexibly supported PV panel arrays, the grid-independent validation is carried out first, and then the case study validation is carried out to ensure the accuracy of the method in this paper. The CFD numerical simulation method is used to obtain the wind load variation of the PV panel array with different tilt angles, different spacing ratios, different wind angles, different heights above ground, different regions, and mountainous conditions. The distribution of wind pressure coefficients on the surface of PV panels with different inclination angles at different spacing ratios was investigated. The results show that the wind load shape coefficients with the increase in tilt angle and height above ground are basically a linear growth; the maximum value of PV shape coefficients appears in the wind angle at 30°, and 150° near the different tilt angles of the flexible PV array group shape coefficients distribution law is inconsistent. Different tilt angles of PV modules with the change rule of the spacing ratio of the wind load are inconsistent and have a greater impact on the wind load, so the PV panel array in all wind direction angles under the regional shape coefficients has a recommended value. The proposed value of the regional shape coefficients at all wind angles and the wind load calculation formula introducing height coefficients and spacing ratio coefficients are given.

Partitioning of wind pressure coefficients on a tall building under interference effect: A cluster analysis approach

This study proposed a cluster analysis-based approach for partitioning wind pressure on tall buildings in densely-packed areas, considering interference effects. By utilizing a modified GK cluster algorithm and leveraging the coordinate positions of pressure taps along with their corresponding wind pressure coefficients (WPC), the study aimed to distinguish different parts of the building surface exhibiting varying wind load characteristics. The adoption of cluster validation indices (CVIs) allowed for the determination of the optimal number of clusters, enhancing the accuracy and reliability of the partitioning process. The resulting clusters effectively captured the distribution of wind pressure, providing valuable insights for wind-resistant design considerations. Overall, the proposed approach demonstrates promising potential in facilitating the design and analysis of tall buildings subjected to complex wind loads in urban environments.

The effects of row spacing and ground clearance on the wind load of photovoltaic (PV) arrays

The accuracy of wind loads is vital for the security and economy of PV power stations. The majority of existing studies focus on the importance of the tilt angle, wind direction, and interference effect on PV modules. However, very few studies investigate the effects of row spacing and ground clearance on wind loads of PV arrays, which probably have considerable influences. The present study combines numerical simulations and wind tunnel tests to explore the impact of row spacing and ground clearance on wind loads. The results reveal that the row spacing considerably influences wind loads, and the influence of ground clearance is inconsiderable. Increasing row spacing notably diminishes the shielding effect of the windward row on subsequent ones. The second row experiences the most noticeable wind load variation when row spacing changes, with the amplitude of wind load variation in the second row being two to three-fold that of the third to eighth rows. The change of ground clearance varies the vortex size and form but exerts an inconsiderable influence on wind loads. The reduction factor is defined to describe the wind loads after the third row, which is suggested to be 0.7 for all tilt angles (β ≥ 15° or β ≤ - 15°) in row spacing from chord length to 5 times chord length in the practice. It should be noted that the wind load on the second row may change the direction at different row spacing. When the row spacing is between double and triple chord lengths, the pressure and torque coefficients obtain the minimum in the present study.

Wind tunnel test study on the wind load variation law of a point focus solar furnace

This work studied the wind load acting on a point focus solar furnace composed of a 110 m2 heliostat and a 77 m2 concentrator through wind tunnel testing. Based on wind tunnel test data under 305 different working conditions, the variation laws of the wind pressure coefficient, power spectral density, and wind load coefficient of the heliostat and concentrator were analyzed. The results showed that due to the interaction between the concentrator and heliostat, the wind speed near the heliostat and concentrator decreased but the turbulence intensity increased, which caused the peak wind load coefficient to rise slightly. The results suggested that a safety factor of 1.1–1.2 should be considered for structural design and optimization of solar furnaces.

An Efficient Calculation Method for Stress and Strain of Concrete Pump Truck Boom Considering Wind Load Variation

Digital twin is the development trend of concrete pump trucks to realize digitalization and intellectualization. The realization of digital twin requires high calculation efficiency and accuracy of the model. As the concrete pump truck works under the wind load, the wind speed and direction on site change frequently and intensely. However, existing methods, such as the finite element method, have the problems of low computational efficiency, high time complexity, and the update frequency being far lower than the frequency of wind change on site. We propose an efficient calculation model for the stress and strain of the pump truck boom based on the back propagation (BP) neural network. The novelty of this work is that when calculating the stress and strain of the boom, the change of the boom posture and the change of the site wind conditions are considered, and the calculation efficiency can be significantly improved. Compared with the finite element simulation, the fitting and prediction accuracy of the stress and strain are more than 99.7%, which can meet the requirements for real-time calculation of the stress and strain of the boom under different attitudes and wind loads in digital twins.

A universal algorithm for linear and quadratic programming in the problems of contact deformation of cable-stayed structures with one-way connections

Problems in production activities that require optimization problems are extremely numerous and very diverse. Optimization approaches are most often associated with the search for the best version of a structure or building. Mathematical methods for solving such problems are developing rapidly and are widely used. They actively and productively penetrate into many areas of scientific research, into engineering and design developments, are an important tool for improving design efficiency throughout the entire process of creating structures. The search for the best design solution is reduced to the selection of a set of parameters that provide a stationary value of the objective function. A wide range of extreme problems of practical orientation, as a rule, in mathematical models contains restrictions on design parameters of the equality-inequality type. In general, their set makes up the content of such a section of mathematics as Mathematical Programming. Due to the fact that there is no single solution method, diversity in research approaches has formed, which divides them into groups, classes, etc. Linear programming (LP), as one of the sections, with a linear objective function and constraints is well studied and successfully applied. Methods of solving problems of nonlinear programming, which includes quadratic programming, are more complex. Therefore, the development of convenient computational schemes is relevant. The essence of this work is that the statements of 2 optimization problems are formalized in a single and convenient form of a symmetric matrix dependence, which makes it possible to obtain an effective (in our opinion) algorithm for their implementation. Namely, a unified scheme for solving both LP and KP problems based on matrix algebra operations is proposed. Quadratic programming (QP), as the second section, also has wide possibilities, in particular, it allows considering the practical tasks of calculating VAT in the mechanics of a deformed solid body under the conditions of contact interaction. Such problems, in particular, include cable-stayed structures with one-way connections and span lengths that can reach tens or hundreds of meters. As an example, the behavior of a model cable-stayed span structure under varying wind loads is considered. The given results may be of interest.

Multivariate Adaptive Regression Spline approach for the assessment of surface mean pressure coefficient on surfaces of C-shaped building

Proper assessment of wind load enables durable design of structures under varying wind load conditions. The accurate prediction of pressure coefficient on any irregular plan shaped buildings is essential for the assessment of wind loads and the structural design. The main objective of this study is to present an equation in the line of Multivariate Adaptive Regression Spline (MARS) approach using experimental data of surface mean pressure coefficient. This developed equation can be used satisfactorily for the prediction of pressure coefficient values accurately on the surfaces of C-shaped buildings. An extensive experimentation was carried out to obtain coefficient of pressure over the surfaces of C-shaped models under varying sizes, corner curvature and angle of incidence in a sub-sonic wind tunnel. The predicted values of pressure coefficient of different C-shaped buildings using developed model are compared with equations developed by Swami and Chandra’s (S&C) and Muehleisen and Patrizi’s (M&P). The comparison indicates that the proposed MARS model predicts pressure coefficient values more accurately than those by S&C and M&P models on frontal as well as side surfaces. Further, the model is used to validate with the actual building, Tokyo Polytechnic University (TPU) data to show the applicability of the proposed equation.

Effect of roof to wall connection stiffness variations on the load sharing and hold-down forces of Australian timber-framed houses

Roof to wall connections (RWCs) play a major role in wind load sharing and load transfer of timber-framed houses. The lack of coherence in the load sharing and load transfer can cause premature failure of timber-framed houses. Thus, it is essential to provide RWCs with adequate strength and stiffness, to ensure the dynamic roof wind loads are adequately shared and transferred through the structural system to the foundations. Typical construction defects in RWCs (i.e. missing nails) reduce the stiffness of the RWCs, introducing discontinuities in load paths, contributing to total roof failure under windstorms. This study combines realistic spatially and temporally varying wind loads, captured from model-scale wind tunnel-studies, with a validated finite element model of the roof structure, that accurately describes the load sharing through the structural system and evaluate the effect of RWC stiffness variations and realistic wind loading variation on the load sharing and hold-down forces of Australian contemporary timber-framed houses. The combined effect of RWC stiffness variations and realistic wind loading variation are compared to the traditional design method approach (i.e. tributary area method and use of simplified design roof pressures from wind loading standard AS/NZS 1170.2 (2011)). Results show that the maximum RWC hold-down force from AS/NZS 1170.2 (2011) is about 10% greater relative than the maximum RWC hold-down force from realistic dynamic wind loads, and overestimates wind loads for most wind angles. The maximum RWC hold-down force derived by the load sharing method with defective connections (i.e. single and double nails missed on the RWCs), induced hold-down forces 10% higher than that of the traditional method at neighbouring RWCs. Further, hold-down force variation between traditional and load sharing methods can increase up to 50% in a real house roof structure, as the stiffness of their RWCs vary throughout the system due to the material non-linearity and construction defects/human errors.

The wind load prediction and comparative study of asmmetric semi-submersible lifting platform based on CFD

In order to accurately predict the wind load of asymmetric offshore structures, this paper studied the wind load of an asymmetric semi-submersible lifting platform based on the CFD software FINE/MARINE, and calculated the wind load of operation state, lifting state and survival state respectively, and compared the results with those of China Classification Society(CCS) specification. The results show that under the same wind speed, the change of wind direction angle has a great influence on the distribution of wind field around the platform. The specification calculation can not fully consider the influence of the shielding effect between the components of the superstructure, therefore, the results are larger than the numerical simulation value. In addition, the wind field distribution near the platform can be used to analyze the variation of wind load, which provides an effective method for wind load prediction and wind field analysis of asymmetric offshore structures.

Numerical Analysis of Wind Loads on Bridges in Sandy Environment

Based on the Euler two-phase model, sand is regarded as a flowing fluid. In the numerical analysis, the sand is simulated as two-phase flow. Wind load variation on the windward side of the bridge under the wind-blown environment is analyzed numerically. Wind load variation on the bridge is studied when the flow velocity, particle size, and sediment concentration are different. This paper’s wind load numerical analysis is compared with the wind load calculated in the Code for Wind Resistance Design of Highway Bridges. Results show that the effect of sand load under wind and sand environment cannot be ignored.

Wind Load Simulation on Cylindrical Air-supported Structure

More and more air-supported structures are used. However，the current wind load shape coefficient can not match engineering design. The CFD technology is utilized to simulate the wind load pressure distribution of rigid half cylindrical shape used for air-supported structures frequently. The shape is found by finite element software ANSYS, and then put into the flow field. RNG ĸ-ε turbulence model based on the Reynolds averaging method and FLUENT software are chose to investigate wind load variation along different wind direction (0°, 30°, 60°, 90°). The results show that the distribution range of extreme negative pressure area is from - 0.9 to - 1.01 at different wind direction angles, and it is easy to separate and form extreme negative pressure area at the two corners close to the windward side. Therefore, enough attention should be paid to the extreme positive pressure area at the bottom of the windward side and the extreme negative pressure area at the top of the membrane face.

Progressive failure analysis of low-rise timber buildings under extreme wind events using a DAD approach

This paper discusses the interaction of low-rise timber buildings with wind loads under significant wind events such as hurricanes. The proposed analysis methodology is capable of predicting the progressive failure of low-rise buildings as a result of the wind-structure interaction for a cost-effective design. It will also assist in evaluating the wind intensity from the observed damage state of buildings. Two deterministic finite-element (FE) models are developed using ANSYS for the full-scale numerical simulation. The first model with a simple building configuration is used for the validation of a numerical modeling methodology in the ultimate failure range. It also serves to validate the proposed progressive failure analysis process via the calibration from the corresponding wind tests that can simulate failures. Then, this analysis methodology is used to study the successive stages of damage on the second model to unveil its potential applications on a more representative residential buildings in U.S. Spatiotemporally varying wind loads are applied with the purpose of expanding the application of database-assisted design (DAD) approach from the linear range to the nonlinear range and finally to the stage-wise failures, which is a necessity of the vulnerability assessment and is critical for the damage and loss prediction for the insurance industry.

Design and Analysis of Wind Turbine Rotors Using Hinged Structures and Rods

Light weight and high stiffness are key design factors in ensuring cost effectiveness and reliability of wind turbines, especially for the inboard region of the rotor blades. In this study, several novel designs were developed to improve the mechanical performance of the rotor. Experiments were performed on an isolated blade incorporating the new features of a hinged structure and rods. The results validated the effectiveness of these features at alleviating the root-bending moment of the blade under varying wind loads and enhancing the stiffness of the blade. A numerical investigation was carried out to further examine the bending moment distribution, shear and axial force, and rod tension of these novel rotor designs under uniform loads. Longitudinal geometrical variations of the blade were considered in the model. Results showed that two designs realized a favorable bending moment distribution and improved the modal frequencies of the edgewise modes: bisymmetrical rods on a single-hinged structure and interveined symmetrical rods on a cantilevered structure. However, these designs have different deformation mechanisms. In addition, the first group of edgewise modal frequencies of these two designs were improved compared with the traditional rotor design. Their potential values in the application to the design of a lightweight, high-stiffness, and reliable wind turbine rotor were discussed.

Effect of Wind on the Relation of Leaf N, P Stoichiometry with Leaf Morphology in Quercus Species

Leaf nitrogen (N) and phosphorus (P) stoichiometry correlates closely to leaf morphology, which is strongly impacted by wind at multiple scales. However, it is not clear how leaf N, P stoichiometry and its relationship to leaf morphology changes with wind load. We determined the leaf N and P concentrations and leaf morphology—including specific leaf area (SLA) and leaf dissection index (LDI)—for eight Quercus species under a simulated wind load for seven months. Leaf N and P concentrations increased significantly under these conditions for Quercus acutissima, Quercus rubra, Quercus texana, and Quercus palustris—which have elliptic leaves—due to their higher N, P requirements and a resultant leaf biomass decrease, which is a tolerance strategy for Quercus species under a wind load. Leaf N:P was relatively stable under wind for all species, which supports stoichiometric homeostasis. Leaf N concentrations showed a positive correlation to SLA, leaf N and P concentrations showed positive correlations to LDI under each wind treatment, and the slope of correlations was not affected by wind, which indicates synchronous variations between leaf stoichiometry and leaf morphology under wind. However, the intercept of correlations was affected by wind, and leaf N and P use efficiency decreased under the wind load, which suggests that the Quercus species changes from “fast investment-return” in the control to “slow investment-return” under windy conditions. These results will be valuable to understanding functional strategies for plants under varying wind loads, especially synchronous variations in leaf traits along a wind gradient.

Variations in wind load on tall buildings due to urban development

Due to the continuous urban development, it becomes necessary to investigate the complex aerodynamic interactions within the built environment. These interactions lead to a significant variation in wind loads on structural systems and non-structural components. With the change in urban topology, an individual building immersed in a complex surrounding can experience different flow mechanisms, such as wake effects and channeling. These flow mechanisms depend on the shape, height and location of the surrounding structures, which alter with the city development. The current study investigates the risks associated with changing wind loads as urban surroundings develop. The study adopts two cases. Case I examines the change in wind loads on a typical tall building with generic surrounding configuration of different heights. For Case II, the built environment of the Financial District, Toronto is examined for three development stages. The changes in urban topology are found to have different impacts on structural and non-structural elements from wind hazard perspective. Based on the study cases, mean wind pressures are reduced while fluctuations are increased as the urban environment becomes denser. The effect of increased pressure fluctuations on cladding elements is viewed as a higher wind risk due to damage accumulation.

Natural characteristic analysis of wind turbine drivetrain considering flexible supporting

The mechanical system of wind turbine is much complicated and can be divided into the drivetrain and supporting portions. The drivetrain consists of wheel, main shaft, gearbox, generator, etc. and the supporting portion mainly consists of a tower and a cabin. In order to reduce the unit cost of electricity, the capacity and size of wind turbine are increased gradually in the past years. Meanwhile, with the increase of the wind turbine height, the tower actually becomes more flexible as the supporting part. And the influence of the supporting tower flexibility becomes stronger due to the varying wind loads both in magnitude and direction. Using the rigid–flexible coupling multibody dynamic theory, the coupled dynamic model of the wind turbine drive train was developed considering the flexible supporting. Then the natural characteristics of the system were computed and investigated. For the dynamic modeling, the blades, the tower and main shaft were modeled as flexible bodies, while the other components, such as the hub and the gearbox, were modeled as rigid bodies. The potential resonance frequencies of the system were discussed through the Campbell diagram and the modal energy distribution analysis. The results show that the natural frequency of swing mode shapes for the tower was 0.399 Hz and 0.405 Hz. The first natural frequency of drivetrain, which represented a torsional vibration mode, was 1.64 Hz. From the Campbell diagram and the modal energy distribution analysis, resonances would not occur within the normal operating speed range for the drivetrain. And a comparison analysis indicated that the flexible supports would increase the bearing loads along axial direction and radial direction, especially in main shaft and torque arm, but that influence was not obvious at parallel stage. However, to some extent, the flexible supports can decrease the loads fluctuation of drivetrain. Finally, the online vibration experiments were carried out in the wind field. The vibration characteristics of the wind turbine drivetrain were analyzed and the experimental results also compared well with the theoretical dynamic results.

Reliability-based design optimization of wind turbine blades for fatigue life under dynamic wind load uncertainty

This paper studies reliability-based design optimization (RBDO) of a 5-MW wind turbine blade for designing reliable as well as economical wind turbine blades. A novel dynamic wind load uncertainty model has been developed using 249 groups of wind data to consider wind load variation over a large spatiotemporal range. The probability of fatigue failure during a 20-year service life is estimated using the uncertainty model in the RBDO process and is reduced to meet a desired target reliability. Meanwhile, the cost of composite materials used in the blade is minimized by optimizing the composite laminate thicknesses of the blade. In order to obtain the RBDO optimum design efficiently, deterministic design optimization (DDO) of the 5-MW wind turbine blade is carried out first using the mean wind load obtained from the wind load uncertainty model. The RBDO is then initiated from the DDO optimum. During the RBDO iterations, fatigue hotspots for RBDO are identified among the laminate section points. For an efficient RBDO process, surrogate models of 10-min fatigue damages D10 at the hotspots are accurately created using the Kriging method. Using the wind load uncertainty model and surrogate models, probability of fatigue failure during a 20-year lifespan at the hotspots and the design sensitivities are calculated at given design points. Using the probability of fatigue failure and design sensitivity, RBDO of the 5-MW wind turbine blade has been successfully carried out, satisfying the target probability of failure of 2.275 %.

Integrating variable wind load, aerodynamic, and structural analyses towards accurate fatigue life prediction in composite wind turbine blades

A comprehensive fatigue analysis framework for composite wind turbine blades has been developed. It includes variable wind loads from wind field simulation and aerodynamic analysis, stress prediction by finite element analysis, and fatigue damage evaluation based on the resulting fatigue data. The variable wind load is represented by a joint distribution of mean wind speed and turbulence intensity. In order to simulate realistic wind loads applied on the blade while maintaining affordable computational time, the sectional surface pressure fields obtained from the potential flow aerodynamics model XFOIL are transformed to match the lift, drag, and moment coefficients obtained using AeroDyn. Thus, the modified pressure distribution includes the effect of dynamic stall, rotation, and wake effects on the blade aerodynamics. A high-fidelity finite element blade model, in which the design of composite materials can be easily tailored, has been parameterized for detailed stress analysis. The non-proportional multi-axial complex stress states are involved when calculating 10-min fatigue damage of section points through laminate thickness. The annual fatigue damage is calculated based on the 10-min fatigue damage and the joint distribution of 10-min mean wind speed and 10-min turbulence intensity. Consequently, the blade fatigue effect due to not only the mean wind speed and the atmospheric turbulence in the short term, but also the wind load variation in a large spatiotemporal range, can be investigated. The developed fatigue analysis framework can facilitate reliability analysis and reliability-based design optimization of composite wind turbine blades.

Upgrading a Shrouded Wind Turbine with a Self-Adaptive Flanged Diffuser

In this paper, a self-adaptive flange is proposed for the wind turbine shrouded by a flanged diffuser to reduce the wind loads acting on the flanged diffuser at high wind velocities. The self-adaptive flange can maintain the advantages of the flanged diffuser at wind velocities lower than the rated velocity and reduce the wind loads acting on the diffuser and blades at higher wind velocities. Numerical analyses of fluid-structure interactions are carried out to investigate the flow field around the diffuser with a self-adaptive flange and the variation of wind load acting on the diffuser due to the reconfiguration of the self-adaptive flange at various wind velocities. Numerical results show that the wind load acting on the total flanged diffuser can be reduced by about 35% at 60 m/s due to the reconfiguration of the self-adaptive flange.

Experimental Validation of Theoretical Heliostat Wind Loads

Abstract In the current concentrated solar power (CSP) context central receiver systems seems to be the most promising technology with the highest cost reduction potential. In the construction of such plants the solar field represents one of the largest investments, a fact which has made cost reduction of these elements become the main target for many actors of the solar thermal sector. Therefore, the design of cost efficient heliostats has become a major interest. One of the design challenges is to develop a heliostat which is able to withstand all foreseen mechanical loads, while at the same time have reduce costs by avoiding unnecessary safety margins. To achieve this goal a good knowledge of expected wind loads onto the support structure and drive mechanism is crucial. In this paper a heliostat prototype, equipped with measuring devices, is deployed to a test site in order to measure the true mechanical stresses suffered due to varying wind loads. These data together with the information about wind speed and direction is then used to validate theoretical loads determined via formulations extracted from wind tunnel experiments. It is shown, that for low turbulence conditions the theoretical values correspond well to the measured values; however, for turbulent wind conditions a significant difference is detected. As those conditions are difficult to simulate in wind tunnels or CFD simulations, this shows the importance of on-site testing of new heliostat designs.