• Magazine of the Korean Society of Agricultural Engineers
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• v.18 no.2
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• pp.4089-4095
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• 1976

The safety of shore structure including the sea dipe is largely affected by typhoon. Accordingly it is desirable to analize the typhoon and determine the wind direction and velocity for use in planning and design of the structure. This method was adopted for the design of the Yong San Gang Estuary Dam. A comparative study of the results of typhoon analysis with the meteorological data obtained through actual observation is summarized as follows; (1) 62% of the typhoons occur during May to June in a year, and 62% of the typhoons which have an influence on the Korean peninsula, especially the proposed estuary dam fsite, proceed eastward through the zone in lat. 36$^{\circ}$-37$^{\circ}$N. Such typhoons occur two to three times a year on the average. (2) Data on typhoon "SARL" were used as a model case in designing the estuary dam, where it was proved that a southwesterly wind had a maximum velocity of 30m/sec in case r=150km, ${\alpha}$=120$^{\circ}$. Within the range of 22$^{\circ}$30'on the right and left side of the fetch line of the estuary dam, the wind direction varied SSW\longrightarrowSW\longrightarrowWSW, and the wind velocity varied 29m/sec\longrightarrow30m/sec\longrightarrow125m/sec. Such phenomemum lasted for five hours. (3) An analysis of data obtained during 44 years at Mok Po Meteorological Station shows that a wind with a velocity of some 25m/sec occurred twelve times in the S-direction and two times in the SW-direction, while that with a velocity of 30m/sec occurred three times in the S-direction, three times in the SSW-direction and one time in the SW-direction. The wind which had an influence on the estuary dam had a direction of SSW\longrightarrowSW\longrightarrowWSW and a velocity of min. 30m/sec. Actually, a wind with a max. velocity of 31.3m/sec occurred in the SSW-direction on March 15 and 16, 1956 where the mean velocity during two hours was 28m/sec and that during four hours was 24.6m/sec. (4) The data obtained through actual observation show that when the velocity is low, the wind with a fixed direction lasts long, and when the velocity is high, it is short-lived. It is difficult to determine the velocity of a wind which blows in a fixed direction for consecutive two or four hours. Therefore, the values obtained through typhoon analysis are larger that those obtained through actual observation, and hence, it is resonable to use the analyzed valuse for design of the estuary dam and shore structures. (5) The greatest effect was had on the estuary dam when typhoon was proceeding at a velocity of 29.71m/sec in the direction of ${\alpha}$=120$^{\circ}$(SW) at a point of R=150km from the center of the typhoon.

• Wind and Structures
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• v.3 no.3
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• pp.177-191
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• 2000

This paper presents an approach for evaluating directionality effects for both wind speeds and wind loads in hurricane-prone regions. The focus of this study is on directional wind loads on low-rise structures. Using event-based simulation, hurricane directionality effects are determined for an open-terrain condition at various locations in the southeastern United States. The wind speed (or wind load) directionality factor, defined as the ratio of the N-year mean recurrence interval (MRI) wind speed (or wind load) in each direction to the non-directional N-year MRI wind speed (or wind load), is less than one but increases toward unity with increasing MRI. Thus, the degree of conservatism that results from neglecting directionality effects decreases with increasing MRI. It may be desirable to account for local exposure effects (siting effects such as shielding, orientation, etc.) in design. To account for these effects in a directionality adjustment, the factor described above for open terrain would need to be transformed to other terrains/exposures. A "local" directionality factor, therefore, must effectively combine these two adjustments (event directionality and siting or local exposure directionality). By also considering the direction-specific aerodynamic coefficient, a direction-dependent wind load can be evaluated. While the data necessary to make predictions of directional wind loads may not routinely be available in the case of low-rise structures, the concept is discussed and illustrated in this paper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.543-548
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• 2011

New concept of wind energy conversion system is proposed to increase the energy density at a given working space. The quality of wind for wind power generation is depend on its direction and speed. However, the quality is not good on land because wind direction is changeable all the time and the speed as well. The most popularly operated wind turbine system is an axial-flow free turbine. But its conversion efficiency is less than 30% and even less than 20% considering the operating time. In this research, a cross-flow type wind turbine system is proposed with a convergent-divergent duct system to accelerate the low speed wind at the inlet of the wind turbine. Inlet guide vane is also introduced to the wind turbine system to have continuous power generation under the change of wind direction. In here, the availability of wind energy generation is evaluated with the change of the size of the inlet guide vane and the optimum geometry of the turbine impeller blade was found for the innovative wind power generation system.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.2
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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.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.2
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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.

• Smart Structures and Systems
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• v.26 no.4
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• pp.435-449
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• 2020

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

• Journal of Environmental Science International
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• v.19 no.10
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• pp.1257-1269
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• 2010

In this study the AWS was installed in three areas to analyze creation and characteristics of local wind circulation through observation. According to the result, in night time when mountain wind is well developed showed temperature in A area located in Dalbigol valley and B area adjacent with the valley was lower than C area located in the lowland of the center of city by $1.5\sim4^{\circ}C$. The wind speed was also shown two times stronger than C area. In addition, in terms of wind direction, A and B areas showed east wind consistently according to topographic shapes of Dalbigol valley with high altitude and residential sites of lowland with low altitude. Although the C area didn't show big changes in wind direction due to the effects of city structures, east wind is often seen so mountain wind from Dalbigol valley is found to have an effect at least. Through the analysis of temperature, wind speed, and wind direction, nigh time showed relatively cold mountain wind blew following Dalbigol valley, throughout residential sites and to the center of city with lowland. During the daytime, the temperature in the city with lowland and residential sites is constantly higher than A area located in Dalbigol valley, and strong wind speed following Dalbigol valley, and three areas have $200\sim300^{\circ}$ of main wind direction, so west valley wind throughout the city with lowland and following Dalbigol is clearly formed.

• Smart Structures and Systems
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• v.21 no.5
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• pp.601-609
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• 2018

The estimated probabilistic model of wind data based on the conventional approach may have high discrepancy compared with the true distribution because of the uncertainty caused by the instrument error and limited monitoring data. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method has been developed in the companion paper and is conducted to formulate the joint probability density function (PDF) of wind speed and direction using the wind monitoring data of the investigated bridge. The established bivariate model of wind speed and direction only represents the features of available wind monitoring data. To characterize the stochastic properties of the wind parameters with the subsequent wind monitoring data, in this study, Bayesian inference approach considering the uncertainty is proposed to update the wind parameters in the bivariate probabilistic model. The slice sampling algorithm of Markov chain Monte Carlo (MCMC) method is applied to establish the multi-dimensional and complex posterior distribution which is analytically intractable. The numerical simulation examples for univariate and bivariate models are carried out to verify the effectiveness of the proposed method. In addition, the proposed Bayesian inference approach is used to update and optimize the parameters in the bivariate model using the wind monitoring data from the investigated bridge. The results indicate that the proposed Bayesian inference approach is feasible and can be employed to predict the bivariate distribution of wind speed and direction with limited monitoring data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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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.

• Wind and Structures
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• v.23 no.5
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• pp.465-483
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• 2016

This study aims to enhance the understanding of the surface pressure distribution around rectangular bodies, by considering aspects such as the suction pressure at the leading edge on the top and side faces when the body aspect ratio and wind direction are changed. We carried out wind tunnel measurements and numerical simulations of flow around a series of rectangular bodies (a cube and two rectangular bodies) that were placed in a deep turbulent boundary layer. Based on a modern numerical platform, the Navier-Stokes equations with the typical two-equation model (i.e., the standard $k-{\varepsilon}$ model) were solved, and the results were compared with the wind tunnel measurement data. Regarding the turbulence model, the results of the $k-{\varepsilon}$ model are in overall agreement with the experimental results, including the existing data. However, because of the blockage effects in the computational domain, the pressure recovery region is underpredicted compared to the experimental data. In addition, the $k-{\varepsilon}$ model sometimes will fail to capture the exact flow features. The primary emphasis in this study is on the flow characteristics around rectangular bodies with various aspect ratios and approaching wind directions. The aspect ratio and wind direction influence the type of wake that is generated and ultimately the structural loading and pressure, and in particular, the structural excitation. The results show that the surface pressure variation is highly dependent upon the approaching wind direction, especially on the top and side faces of the cube. In addition, the transverse width has a substantial effect on the variations in surface pressure around the bodies, while the longitudinal length has less influence compared to the transverse width.