• Journal of the Korean Solar Energy Society
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• v.34 no.2
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• pp.82-90
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• 2014

The MERRA reanalysis data provided online by NASA was applied to predict the annual energy productions of two largest wind farms in Korea. The two wind farms, Gangwon wind farm and Yeongyang wind farm, are located on complex terrain. For the prediction, a commercial CFD program, WindSim, was used. The annual energy productions of the two wind farms were obtained for three separate years of MERRA data from June 2007 to May 2012, and the results were compared with the measured values listed in the CDM reports of the two wind farms. As the result, the prediction errors of six comparisons were within 9 percent when the availabilities of the wind farms were assumed to be 100 percent. Although further investigations are necessary, the MERRA reanalysis data seem useful tentatively to predict adjacent wind resources when measurement data are not available.

• Wind and Structures
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• v.21 no.3
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• pp.353-367
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• 2015

As concrete wind-turbine towers are increasingly being used in wind-farm construction, there is a growing need to understand the behavior of concrete wind-turbine towers. In particular, experimental evaluations of concrete wind-turbine towers are necessary to demonstrate the dynamic characteristics and load-carrying capacity of such towers. This paper describes a model test of a prestressed concrete wind-turbine tower that examines the dynamic characteristics and load-carrying performance of the tower. Additionally, a numerical model is presented and used to verify the design approach. The test results indicate that the first natural frequency of the prestressed concrete wind turbine tower is 0.395 Hz which lies between frequencies 1P and 3P (0.25-0.51 Hz). The damper ratio is 3.3%. The maximum concrete compression stresses are less than the concrete design compression strength, the maximum tensile stresses are less than zero and the prestressed strand stresses are less than the design strength under both the serviceability and ultimate limit state loads. The maximum displacement of the tower top are 331 mm and 648 mm for the serviceability limit state and ultimate limit state, respectively, which is less than L/100 = 1000 mm. Compared with traditional tall wind-turbine steel towers, the prestressed concrete tower has better material damping properties, potential lower maintenance cost, and lower construction costs. Thus, the prestressed concrete wind-turbine tower could be an innovative engineering solution for multi-megawatt wind turbine towers, in particular those that are taller than 100 m.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.489-494
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• 2015

As the world-wide supply of fossil fuel sources decreases, the need for efficient energy conservation in addition to developing green energy technologies becomes critical. Wind energy is now regarded as one of the most rapidly expanding energy sources in the world. However, due to the high cost for the foundation of large turbines and the high wind speed (over 12 m/s) required, it is very difficult to establish inland wind power plants. In order to solve issues mentioned above, experiments were performed using the small wind power system operated in a low wind speed. In this research, inland wind condition was first analyzed, and 300 W and 1 kW small wind power generators were then installed on a roof and efficiencies of generating electricities were compared.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1812-1821
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• 2014

Wind has been a rapidly growing renewable power source for the last twenty years. Since wind behavior is chaotic in nature, its forecasting is not easy. At the same time, developing an accurate forecasting method is essential when wind farms are integrated into the power grid. In fact, wind speed forecasting tools can solve issues related to grid stability and reserve allocation. In this paper 30 hours ahead wind speed profile forecast is proposed using Adaptive Wavelet Neural Network (AWNN). The implemented AWNN uses a Mexican hat mother Wavelet, and Morlet Mother Wavelet for seven, eight and nine levels decompositions. For wind speed forecasting, the time series data on wind speed has been gathered from the National Renewable Energy Laboratory (NREL) website. In this work, hourly averaged 10-min wind speed data sets for the year 2004 in the Midwest ISO region (site number 7263) is taken for analysis. Data sets are normalized in the range of [-1, 1] to improve the training performance of forecasting models. Total 8760 samples were taken for this forecasting analysis. After the forecasting phase, statistical parameters are calculated to evaluate system accuracy, comparing different configurations.

• Wind and Structures
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• v.10 no.1
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• pp.45-60
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• 2007

Transmission tower is a vital component in electrical system. In order to accurately compute the dynamic response and reliability of transmission tower under the excitation of wind loading, a new method termed as probability density evolution method (PDEM) is introduced in the paper. The PDEM had been proved to be of high accuracy and efficiency in most kinds of stochastic structural analysis. Consequently, it is very hopeful for the above needs to apply the PDEM in dynamic response of wind-excited transmission towers. Meanwhile, this paper explores the wind stochastic field from stochastic Fourier spectrum. Based on this new viewpoint, the basic random parameters of the wind stochastic field, the roughness length $z_0$ and the mean wind velocity at 10 m heigh $U_{10}$, as well as their probability density functions, are investigated. A latticed steel transmission tower subject to wind loading is studied in detail. It is shown that not only the statistic quantities of the dynamic response, but also the instantaneous PDF of the response and the time varying reliability can be worked out by the proposed method. The results demonstrate that the PDEM is feasible and efficient in the dynamic response and reliability analysis of wind-excited transmission towers.

• Journal of Ocean Engineering and Technology
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• v.29 no.4
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• pp.283-290
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• 2015

This paper presents the results of a numerical study on the towing characteristics of a barge under various wind conditions. First, stability criteria, including the wind force, were derived based on the linear motion equations of a towed vessel. The effect of the wind force on the towing stability was investigated using stability criteria. Next, towing simulations were carried out using a nonlinear time-domain simulation method. In this case, the towline was modeled as a simple spring-damper, and the wind force was computed using the wind coefficient from CFD calculations. Simulations were conducted for a barge under a constant towing speed and constant wind speed conditions. The effect of the wind direction on the slewing motion was also observed. In addition, a series of numerical simulations using variable wind speeds were performed for the present barge with and without a skeg.

• Wind and Structures
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• v.32 no.5
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• pp.509-520
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• 2021

The streamlined box is a common type of girders for long-span suspension bridges. Spanning deep canyons, long-span bridges are frequently attacked by strong winds with large angles of attack. In this situation, the flow field around the streamlined box changes significantly, leading to reduction of the flutter performance. The wind fairings have different effects on the flutter performance. Therefore, this study examines the flutter performance of box girders with different wind fairings at large angles of attack. Computational fluid dynamics (CFD) simulations were carried out to extract the flutter derivatives, and the critical flutter state of a long-span bridge was determined. Further comparisons of the wind fairings were investigated by a rapid method which is related to the input energy by the aerodynamic force. The results show that a reasonable type of wind fairings could improve the flutter performance of long-span bridges at large angles of attack. For the torsional flutter instability, the wind fairings weaken the adverse effect of the vortex attaching to the girder, and a sharper one could achieve a better result. According to the input energies on the girder with different wind fairings, the symmetrical wind fairings are more beneficial to the flutter performance

• Wind and Structures
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• v.35 no.5
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• pp.297-307
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• 2022

Over the past few decades, the use of wind tunnels has been increasing as a result of the rapid growth of cities and the urge to build taller and non-typical structures. While the accuracy of a wind tunnel study on a tall building requires several aspects, the precise extraction of wind pressure plays a significant role in a successful pressure test. In this research study, a low-cost expandable synchronous multi-pressure sensing system (SMPSS) was developed and validated at Ryerson University's wind tunnel (RU-WT) using electronically scanning pressure sensors for wind tunnel tests. The pressure system consists of an expandable 128 pressure sensors connected to a compact data acquisition and a host workstation. The developed system was examined and validated to be used for tall buildings by comparing mean, root mean square (RMS), and power spectral density (PSD) for the base moments coefficients with the available data from the literature. In addition, the system was examined for evaluating the mean and RMS pressure distribution on a standard low-rise building and were found to be in good agreement with the validation data.

• Wind and Structures
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• v.37 no.3
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• pp.245-254
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• 2023

In this paper, the wind-induced response of Jiayuguan wooden building (world cultural heritage) in Northwest China was studied. ANSYS finite element software was used to establish four kinds of building models under different working conditions and carry out modal analysis. The simulation results were compared with the field dynamic test results, obtaining the model which reflects the real vibration characteristics of the wooden tower. Time history data of fluctuating wind speed was obtained by MATLAB programming. Time domain method and ANSYS were used to analyze the wind-induced vibration response time history of Jiayuguan wooden building, obtaining the displacement time history curve of the structure. It was suggested that the wind-induced vibration coefficient of Jiayuguan wooden building is 1.76. Through analysis of the performance of the building under equivalent static wind load, the maximum displacement occurs in the three-story wall, gold column and the whole roof area, and the maximum displacement of the building is 5.39 cm. The ratio of the maximum stress value to the allowable value of wood tensile strength is 45 %. The research results can provide reference for the wind resistant design and protection of ancient buildings with similar structure to Jiayuguan wooden tower.

• Wind and Structures
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• v.36 no.6
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• pp.367-377
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• 2023

This study proposes a few-shot learning model for extrapolating the wind pressure of scaled experiments to full-scale measurements. The proposed ML model can use scaled experimental data and a few full-scale tests to accurately predict the remaining full-scale data points (for new specimens). This model focuses on extrapolating the prediction to different scales while existing approaches are not capable of accurately extrapolating from scaled data to full-scale data in the wind engineering domain. Also, the scaling issue observed in wind tunnel tests can be partially resolved via the proposed approach. The proposed model obtained a low mean-squared error and a high coefficient of determination for the mean and standard deviation wind pressure coefficients of the full-scale dataset. A parametric study is carried out to investigate the influence of the number of selected shots. This technique is the first of its kind as it is the first time an ML model has been used in the wind engineering field to deal with extrapolation in wind performance prediction. With the advantages of the few-shot learning model, physical wind tunnel experiments can be reduced to a great extent. The few-shot learning model yields a robust, efficient, and accurate alternative to extrapolating the prediction performance of structures from various model scales to full-scale.