• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.11-16
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• 2007

This paper describes the cycloidal wind turbine, which is a straight blade vertical axis wind turbine using the cycloidal blade system. Cycloidal blade system consists of several blades rotating about an axis in parallel direction. Each blade changes its pitch angle periodically. Cycloidal wind turbine is different from the previous turbines. The wind turbine operates with optimum rotating forces through active control of the blade to change pitch angle and phase angle according to the changes of wind direction and wind speed. Various numerical experiments were conducted to develop a small vertical axis wind turbine of 1 kW class. For this numerical analysis, the rotor system equips four blades consisting of a symmetric airfoil NACA0018 of 1.0m in span, 0.22m in chord and 1.0m in radius. A general purpose commercial CFD program, STAR-CD, was used for numerical analysis. PCL of MSC/PATRAN was used for efficient parametric auto mesh generation. Variables of wind speed, pitch angle, phase angle and rotating speed were set in the numerical experiments. The generated power was obtained according to the various combinations of these variables. Optimal pitch angle and phase angle of cycloidal blade system were obtained according to the change of the wind direction and the wind speed. Based on data obtained from the above analysis, control device was designed. The wind direction and the wind speed were sensed by a wind indicator and an anemometer. Each blades were actuated to optimal performance values by servo motors.

• Journal of Korean Society for Atmospheric Environment
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• 제8권2호
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• pp.138-145
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• 1992

Dependence of the standard deviation of wind direction fluctuations, ${\sigma}_{\theta}$, on atmospheric stability, averaging time and topography were analysed with the data measured at three sites, Youngjongdo beach of the Yellow Sea, Chuncheon basin and Doam-Dam valley. The results show that the mean value of ${\sigma}_{\theta}$ is large in complex terrain, the Doam-Dam site. It is notable that the large value of ${\sigma}_{\theta}$ at night is associated with the low wind speed and the strong stable condition. In order to study the long-period fluctuations of the wind direction, ${\sigma}_{\theta}$ for longer than 10 minutes averaging time was further analysed using the data obtained at the Chuncheon basin. At the averaging time shorter than 60 minutes, larger ${\sigma}_{\theta}$ is associated with longer averaging time in the strong stable condition. However, ${\sigma}_{\theta}$ was not affected significantly by wind speed and averaging time in neutral conditions. The results of the spectrum analysis for the time series data of wind direction showed that low-frequency fluctuations ranging from 10 to 60 minutes were dominated at the Chuncheon basin in strong stable condition.

• Magazine of the Korean Society of Agricultural Engineers
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• 제38권2호
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• pp.145-151
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• 1996

Wind force coefficients of multi-span arched greenhouses with respect to wind direction of $0^{\circ}$ and $30^{\circ}$ were estimated to give more reasonable coefficient. The conventional and subdivided division types of wind force coefficient distribution diagrams were constructed by using the wind tunnel experimental data. Bending moments on the greenhouses were determined through structural analysis using obtained wind force coefficients, and were analyzed. Because actual wind pressure values on a face of greenhouse varied with locations, the more divisions of wind force coefficient distribution were subdivided, the better distribution type was coincided with actual state. In order to calculate the more accurate section force occurred on the arched greenhouse by the wind loads, it was recommendable that the wind force coefficient distribution should take more subdivision type. The maximum bending moment at the multi-span greenhouse frame at wind direction of $30^{\circ}$ was greater than that at O。, therefore the wind force coefficient at inclined wind direction to the wall was needed to be considered for the multi-span greenhouse structural design.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.262-267
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• 2008

The long-term wind data are reconstructed from the short-term meteorological data to design the 4 MW offshore wind park which will be constructed at Woljeong-ri, Jeju island, Korea. Using two MCP (Measure-Correlate-Predict) models, the relative deviation of wind speed and direction from two neighboring reference weather stations can be regressed at each azimuth sector. The validation of the present method is checked about linear and matrix MCP models for the sets of measured data, and the characteristic wind turbulence is estimated from the ninety-percent percentile of standard deviation in the probability distribution. Using the Gumbel's model, the extreme wind speed of fifty-year return period is predicted by the reconstructed long-term data. The predicted results of this analysis concerning turbulence intensity and extreme wind speed are used for the calculation of fatigue life and extreme load in the design procedure of wind turbine structures at offshore wind farms.

• Wind and Structures
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• 제39권2호
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• pp.85-100
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• 2024

In light of extreme value distribution probability, an improved prediction method of the Recurrence Period Wind Speed (RPWS) is constructed considering wind direction, with the Equivalent Independent Wind Direction Number (EIWDN) introduced as a parameter variable. Firstly, taking the RPWS prediction of Beijing city as an example, the traditional Cook method is used to predict the RPWS of each wind direction based on the measured wind speed data in Beijing area. On basis of the results, the empirical formulae to determine the parameter variables are fitted to construct an improved expression of the non-exceedance probability of the RPWS. In this process, the statistical model of the optimal threshold is established, and thus the independent wind speed samples exceeding the threshold are extracted and fitted to follow the Generalized Pareto Distribution (GPD) model for analysis. In addition, the Extreme Value Type I (EVT I) distribution model is used to predict and analyze the RPWS. To verify its wide applicability, the improved method is further used in cities like Jinan, Nanjing, Wuxi, Shanghai and Shenzhen to predict and analyze the RPWS of each wind direction, and the prediction results are compared against those gained via the traditional Cook method and the whole direction. Results show that the 50-year RPWS results predicted by the improved method are basically consistent with those predicted by the traditional method, and the RPWS prediction values of most wind directions are within the envelope range of the whole wind direction prediction value. Compared with the traditional method, the improved method can readily predict the RPWS under different return periods through empirical formulae, and avoid the repeated operation process and some assumptions in the traditional Cook method, and then improve the efficiency of prediction. In addition, the improved RPWS prediction results corresponding to the GPD model are slightly larger than those of the EVT I distribution model.

• Journal of the Korean Society of Marine Environment & Safety
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• 제12권3호
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• pp.185-192
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• 2006

Distribution of wind direction and wind speed is very important from the viewpoint of ship's safety because it is closely related to the formation and development of sea wave. In this study, the climatological characteristics of monthly wind distribution in a greater coasting area of Korea are analyzed by the ECMWF objective analysis data for the period from 1985 to 1995{11 years). Distributions of wind direction from October to March are very similar and wind speed is strongest in January. The NW'ly and WNW'ly winds at a latitude of 30 degrees N and northward and the NE'ly wind in the Straits of Taiwan and the South China Sea are sustaining and very strong. Distributions of wind direction from June to August are similar and the SW'ly and SSW'ly winds in the South China Sea are strong. The strong Southeast trades exists in the winter hemisphere{Southern Hemisphere). Wind speeds in April, May and September are generally weak.

• Journal of Industrial Technology
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• 제22권A호
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• pp.49-57
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• 2002

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine's hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the Taekwanryung test site are presented using a one-month wind data from a reference meteorological mast and a temporal mast installed at the site of wind turbine. From this analysis, it turns out that the current location of the reference meteorological mast is wrongly determined, and the self-developed codes for the site calibration are working properly. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제28권2A호
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• pp.197-205
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• 2008

In order to estimate mean wind speed in the Gwangyang-Myodo Region, the probability distribution model of extreme values has been used in the statistical analysis of joint distribution probability of daily maximum wind speed and corresponding direction in this paper. For this purpose frequency of daily maximum records at respective stations is inquired into and sample of largest yearly wind speed of sixteen compass direction and non-direction is extracted from daily data of maximum wind speed and appropriate direction of the meteorological observing stations nearby the bridge construction site. These extreme speed records are applied to Gumbel and Weibull distribution model and parameters are estimated through method of moment and method of least squares etc. And also, distribution and parameters are inquired into whether it is fitted through the probability plot correlation coefficient examination. From fitted parameters the largest yearly wind speed of sixteen compass direction and non-direction is extrapolated taking into account factors regarding sample size of data and distance from the bridge construction site according to the appropriate stations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1984-1987
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• 2005

This study evaluate the statical stability of the container crane with respect to the direction of wind load which is varied between $0^{\circ}$ and $180^{\circ}$ and its average velocity is 40m/s. Using wind experimental data and a formula of wind pressure, we figured out the wind load needed to perform a finite element analysis. And we can obtain the variation of reaction forces at each supporting point according to the direction of wind load.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제18권11호
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• pp.16-22
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• 2017

This study examined the status of resident evacuation sites notified to nearby communities, centered on business sites subject to the risk management plan of Incheon, Siheung, and Ansan. Through an analysis of the meteorological data, the direction of improvement of the site selection process for the safe evacuation of chemical accidents was studied. Among a total of 111 evacuation sites, 30 schools were selected the most, and 2-3 sites were usually selected for evacuation. As a result of an analysis of the Incheon meteorological data of 2016, the frequency of occurrences was 18.8525% in the NNE wind direction, 18.0328% in the NNW wind direction, 12.2951% in the WSW wind direction, 9.0164% in the SSE direction, 8.4700% in the SW direction, 6.5574% in the W direction, and 5.7376% in the S direction. The NNE wind direction showed the highest frequency, but the other winds showed a relatively high frequency, indicating that the annual wind direction was not biased toward one side.