• Journal of Korean Society for Atmospheric Environment
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• v.12 no.4
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• pp.407-419
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• 1996

Characteristics of visual air quality in Seoul have been investigated between June 13 and 21, 1994. Optical properties (extinction coefficient and particle scattering coefficient), meteorological parameters (relative humidity, temperature, wind speed, wind direction, and cloud cover), particle characteristics (mass size distribution, components) were measured and analyzed. During measurement periods, northwest wind with less than 2m/sec of wind speed deteriorates visibility. Effects of relative humidity are though to be not a direct factor which influence to visibility through the size change due to hygroscopic species in aerosol. During the smoggy period both the aerosol mass concentration and fine particle fraction of the size distribution are increased compared to the clear period. Sulfate, organic carbon, and elemental carbon in aerosol are the major species in determining the occurrence and severity of a smog in Seoul.

• Journal of Bio-Environment Control
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• v.3 no.1
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• pp.10-19
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• 1994

Wind load is known to be one of major forces to influence the stability of agricultural structures. General flow fields were calculated to determine flow characteristics over the envelop of the following three types of greenhouses with arched roof : single span, twin span greenhouses, and two single span greenhouses apart 3m inbetween. Pressure coefficients along the envelop of greenhouse were numerically calculated by the k-$\varepsilon$ turbulence model, which lead to determine wind forces on it. Curvilinear coordinate for an arched roof and the upwind scheme were adopted for the study. The calculated pressure coefficients were validated with the avaliable data of Japanese Standard and NGAM Standard. The Magnitude of calculated forces over the envelop was not in good accordance with data except the windward wall. Even tile data of Japanese and NGAM Standard for validation deviated a lot from each other in quantity and quality. Such discrepancy may be attributed to different geometric and/or flow configuration conditions for experiments, or the insenstivity of the k-$\varepsilon$ turbulence model to recirculation flow.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.79-85
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• 2016

This paper analyzed the influence of wind power fluctuations in grid frequency of a stand-alone microgrid that is hybrid generation system with diesel generator, wind turbine, and Battery Energy Storage System (BESS). The existing island area power system consists of only diesel generators. So the grid frequency can be controllable from load change. But hybrid generation system with Renewable Energy Sources (RES) such as wind energy that has the intermittent output can bring power quality problems. BESS is one of the ways to improve the intermittent output of the RES. In this paper, we analyzed the role of BESS in a stand-alone microgrid. We designed a modelling of wind power system with squirrel-cage induction generator, diesel power system with synchronous generator, and BESS using transient analysis program PSCAD/EMTDC. And we analyzed the variation of the grid frequency according to the output of BESS.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.535-536
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• 2006

This paper reports investigation into the factors that influence the transient behavior of the wind power generation system following network fault conditions. It is shown that the critical clearing time(CCT) can be affected by various factors contributed by the host network. Such factors include capacity of wind power, power factor, the length of the interfacing line, etc. This investigation is conducted en a simulated grid-connected wind farm using Digsilent Power Factory.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.55-62
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• 2016

The air flows in building caused by thermal buoyancy, known as the stack effect, have a pronounced influence on both the indoor environment (thermal environment, noise, draught and contaminant diffusion) and energy needs in high-rise buildings. Prior studies for airflow in high-rise buildings were focused on the degree of stack effect and countermeasures. The wind pressure was neglected during the calculation of the indoor airflow in high-rise buildings to clarify the effect of thermal buoyancy in previous studies. However, wind is an important driving force of indoor airflows in buildings with the stack effect. In this study, the effect of wind pressure on indoor airflow in high-rise building when the stack effect is dominant in winter was analyzed. In this paper, methods that involved considering the wind pressure in airflow network simulation were analyzed.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.4
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• pp.351-362
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• 2000

To set the similarity conditions between a prototype usually in the field and its reduced-scale model is a crucial part in model tests. No technique is available to keep perfect similarity for this procedure so far. The experimental work using a wind tunnel is not exceptional. based on the field measurements, the effect of stack parameters and wind conditions on the dispersion of stack plume has been investigated in the laboratory. in this paper intensive methodology is focused on matching these similarities. Due to the limitations to keep perfect similarity conditions some simplifications are involved in common. In this study geometric conditions and kinematic conditions using Froude number and Reynolds number have been con-sidered to keep the similarity conditions required. From the tests it is found that the critical Reynolds number (Recrit) is 2,700 when the height of stack discharge is 50mm. The dispersion has a similar trend for the higher Reynolds number than the critical Reynolds number. It is also found that different Froude number does not make any significant influence for the normalized tracer gas concentrations at the recipient providing the same ratio of the wind speed to the discharge speed. No significant effect of stack diameter is observed in the normalized tracer gas concentrations with the same Frounde number. The similarity conditions therefore used in this study are reliable to simulate the conditions in prototype into the wind tunnel tests.

• Wind and Structures
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• v.12 no.2
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• pp.151-177
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• 2009

The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9 m tall by 7.3 m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.301-314
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• 2022

Various studies have been conducted on pedestrian-level wind environments around buildings. With regard to the speed-up mechanism of pedestrian-level winds, there are references to downwash effect due to the vertical pressure gradient of boundary layer flow and venturi effect due to flow blocking by the building. Two factors contribute to increase or decrease of downwash effect: change in twodimensional / three-dimensional air flow pattern (Type 1) and change in downwash wind speed due to building size that does not accompany change in airflow pattern (Type 2). Previous studies have shown that downwash effect has a greater influence in increasing or decreasing the area of strong wind than venturi effect. However, these considerations are derived from the horizontal mean wind speed distribution at pedestrian level and are not the result of three-dimensional flow field around the building. Therefore, in this study, Computational Fluid Dynamics using Large Eddy Simulation were performed to verify the downwash phenomena that contributes to increase in wind speed at pedestrian level.

• Wind and Structures
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• v.18 no.4
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• pp.391-422
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• 2014

The high frequency force balance (HFFB) technique provides convenient measurements of integrated forces on rigid building models in terms of base bending moments and torque and/or base shear forces. These base moments or forces are then used to approximately estimate the generalized forces of building fundamental modes with mode shape corrections. This paper presents an analysis framework for coupled dynamic response of tall buildings with HFFB technique. The empirical mode shape corrections for generalized forces with coupled mode shapes are validated using measurements of synchronous pressures on a square building surface from a wind tunnel. An alternative approach for estimating the mean and background response components directly using HFFB measurements without mode shape corrections is introduced with a discussion on higher mode contributions. The uncertainty in the mode shape corrections and its influence on predicted responses of buildings with both uncoupled and coupled modal shapes are examined. Furthermore, this paper presents a comparison of aerodynamic base moment spectra with available data sets for various tall building configurations. Finally, e-technology aspects in conjunction with HFFB technique such as web-based on-line analysis framework for buildings with uncoupled mode shapes used in NALD (NatHaz Aerodynamic Loads Database) is discussed, which facilitates the use of HFFB data for preliminary design stages of tall buildings subject to wind loads.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.2
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• pp.145-152
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• 2009

In this paper, dynamic instability of plane membrane structures under wind action has been studied. The key to solving the governing equations of membrane structures under wind action is how to obtain the air pressure on membrane. Based on Bernoulli's theorem, fluid pressure has a certain relationship with velocity potential. Velocity potential could be solved according to thin aerofoil theory, where air around the membrane is regarded as a sheet of vortices. In this paper, we take advantage of the most commonly used three-node triangular membrane element and weighted residual-Galerkin method to obtain the determining equation for stability evaluation. Square and rectangular membrane structures are studied. The influence of initial prestressing force and wind direction towards critical wind velocity are also analyzed in this paper.