• Wind and Structures
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• v.37 no.3
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• pp.211-227
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• 2023

To investigate the non-Gaussian feature of fluctuating wind pressures on rectangular high-rise buildings, wind tunnel tests were conducted on scale models with side ratios ranging from 1/9~9 in an open exposure for various wind directions. The high-order statistical moments, time histories, probability density distributions, and peak factors of pressure fluctuations are analyzed. The mixed normal-Weibull distribution, Gumbel-Weibull distribution, and lognormal-Weibull distribution are adopted to fit the probability density distribution of different non-Gaussian wind pressures. Zones of Gaussian and non-Gaussian are classified for rectangular buildings with various side ratios. The results indicate that on the side wall, the non-Gaussian wind pressures are related to the distance from the leading edge. Apart from the non-Gaussianity in the separated flow regions noted by some literature, wind pressures behind the area where reattachment happens present non-Gaussian nature as well. There is a new probability density distribution type of non-Gaussian wind pressure which has both long positive and negative tail found behind the reattachment regions. The correlation coefficient of wind pressures is proved to reflect the non-Gaussianity and a new method to estimate the mean reattachment length of rectangular high-rise building side wall is proposed by evaluating the correlation coefficient. For rectangular high-rise buildings, the mean reattachment length calculated by the correlation coefficient method along the height changes in a parabolic shape. Distributions of Gaussian and non-Gaussian wind pressures vary with side ratios. It is inappropriate to estimate the extreme loads of wind pressures using a fixed peak factor. The trend of the peak factor with side ratios on different walls is given.

• Journal of Radiation Protection and Research
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• v.29 no.3
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• pp.205-212
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• 2004

Three-dimensional wind field and atmospheric dispersion models have been developed for estimating the concentration distributions of radioactive materials released into atmosphere. The field tracer experiment near the Kori nuclear power plant located over complex terrain was carried out for validating the atmospheric dispersion model. The wind fields were one of the most important factors for calculating the concentration. Therefore several numerical simulations using the measured wind data were performed to get more accurate concentration distributions compared with the analyzed values of the tracer gas. The calculated concentration distributions agreed well in the case of the usage of the more measured wind data in wind field model.

• 한국해양학회지
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• v.15 no.1
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• pp.1-7
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• 1980

The results of measurements of shear current induced in water by wind in wind wave tunnel are presented briefly. The shear current distributions are found to fit reasonably well an exponentiall form. This form was used to estimate surface velocity and boundary layer thickness used in stability analysis. An analysis of hydrodynamic stability of the shear current was carried out, using a broken line as an approximate profile, to see the stability as a possible mechanism of wind wave generation. Comparison between experimental results and theoretical ones shows that there exists a large discrepancy particularly in phase velocity and hydrodynamic instability of the shear current seems not to be the basic mechanism of wind wave generation.

• Wind and Structures
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• v.28 no.6
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• pp.369-380
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• 2019

Statistical distributions are very useful in describing wind speed characteristics and in predicting wind power potential of a specified region. Although the Weibull distribution is the most popular one in wind energy literature, it does not seem to be able to perfectly fit all the investigated wind speed data in nature. Thus, many studies are still being conducted to find flexible distribution for modelling wind speed data. In this study, we propose a new Odd-Burr Rayleigh distribution for wind speed characterization. The Odd-Burr Rayleigh distribution with two shape parameters is flexible enough to model different shapes of wind speed data and thus it can be an alternative wind speed distribution for the assessment of wind energy potential. Therefore, suitability of the Odd-Burr Rayleigh distribution is investigated on real wind speed data taken from different regions in the South Africa. Numerical results of the conducted analysis confirm that the new Odd-Burr Rayleigh distribution is suitable for modelling most of the considered real wind speed cases and it also can be used for predicting wind power.

• Wind and Structures
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• v.13 no.1
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• pp.57-82
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• 2010

The 486m-long roof of Shenzhen Citizens Centre is one of the world's longest spatial lattice roof structures. A comprehensive numerical study of wind effects on the long-span structure is presented in this paper. The discretizing and synthesizing of random flow generation technique (DSRFG) recently proposed by two of the authors (Huang and Li 2008) was adopted to produce a spatially correlated turbulent inflow field for the simulation study. The distributions and characteristics of wind loads on the roof were numerically evaluated by Computational Fluid Dynamics (CFD) methods, in which Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes Equations (RANS) Model were employed. The main objective of this study is to explore a useful approach for estimations of wind effects on complex curved roof by CFD techniques. In parallel with the numerical investigation, simultaneous pressure measurements on the entire roof were made in a boundary layer wind tunnel to determine mean, fluctuating and peak pressure coefficient distributions, and spectra, spatial correlation coefficients and probability characteristics of pressure fluctuations. Numerical results were then compared with these experimentally determined data for validating the numerical methods. The comparative study demonstrated that the LES integrated with the DSRFG technique could provide satisfactory prediction of wind effects on the long-span roof with complex shape, especially on separation zones along leading eaves where the worst negative wind-induced pressures commonly occur. The recommended LES and inflow turbulence generation technique as well as associated numerical treatments are useful for structural engineers to assess wind effects on a long-span roof at its design stage.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.3 s.26
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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.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.5-9
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• 2010

A numerical wind tunnel simulation is performed in order to predict wind loads acting on a building. The aim of the present study is to suggest a guideline for the numerical wind tunnel analysis, which could provide more detail wind load distributions compared to the wind code and expensive wind tunnel experiments. To validate the present numerical simulation, wind-induced loads on a 6 m cube model is predicted. Atmospheric boundary layer is used as a inlet boundary condition. Various effect of numerical methods are investigated such as size of computational domain, grid density, turbulence model and discretization scheme. The appropriate procedure for the numerical wind tunnel analysis is suggested through the present study.

• Wind and Structures
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• v.12 no.1
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• pp.1-19
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• 2009

In this paper, the airflow around an ideal thin plate (hereafter referred to as ITP) with various ratios of central slot is simulated by using the finite-difference-method (FDM)-based Arbitrary-Lagrangian-Eulerian descriptions for the rigid oscillating body. The numerical procedure employs the second-order projection scheme to decouple the governing equations, and the multigrid algorithm with three levels to improve the computational efficiency in evaluating of the pressure equation. The present CFD method is validated through comparing the computed flutter derivatives of the ITP without slot to Theodorsen analytical solutions. Then, the unsteady aerodynamics of the ITP with and without central slot is investigated. It is found that even a smaller ratio of central slot of the ITP has notable effects on pressure distributions of the downstream section, and the pressure distributions on the downstream section will further be significantly affected by the slot ratio and the reduced wind speeds. Continuous increase of $A_2^*$ with the increase of central slot may be the key feature of the slotted ITP. Finally, flutter analyses based on the flutter derivatives of the slotted ITP are performed, and moreover, flutter instabilities of a scaled sectional model of a twin-deck bridge with various ratios of deck slot are investigated. The results confirm that the central slot is effective to improve bridge flutter stabilities, and that the flutter critical wind speeds increase with the increase of slot ratio.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.478-486
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• 1993

For satisfactory greenhouse culture, environmental factors must be kept in proper conditions. Therefore, it is important to know relations between environmental conditions and greenhouse systems. In this study, the environment variations and distributions in different types of greenhouses were measured and analyzed. The elements of environment analyzed were temperature , relative humidity, illumination, carbon dioxide and wind velocity. The analyzed greenhouse types were three different types. One of them, A type, was propagation model type by government and the other one, B type, was multiple continuous arches type which was made by farmers himself. The last one, C type, was single arch type which has no environment control system without manual temperature keeping method. The results of this study can be used for reasonable greenhouse environments managements and control.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.177.1-177.1
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• 2010

Large offshore wind farms have actively been developed in order to meet the needs for wind energy since the land-based wind farms have almost been fully developed especially in Europe. The key problem for the construction of offshore wind farms may be on the high cost of energy compared to land-based ones. NREL (National Renewable Energy Laboratory) has developed a spreadsheet-based tool to estimate the cost of wind-generated electricity from both land-based and offshore wind turbines. Component formulas for various kinds and scales of wind turbines were made using available field data. Annual energy production has been estimated based on the Weibull probability distributions of wind. In this paper, this NREL estimation model is introduced and applied to the offshore wind turbines now under designing or in production in Korea, and the result is discussed.