• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.125-132
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• 2018

The biggest impact on the cladding design of buildings is wind loads. Wind tunnel tests were conducted to examine the applicability of current wind load standards about membrane retractable roof spatial structure. A dome model with a circular shape that is retractable to the center of the dome was made (Opening ratio = 0, 10, 30, 50). In addition, height adjustable turntables were made and tested with five patterns with H/D = 0.1, 0.2, 0.3, 0.4 and 0.5. The maximum wind pressure coefficient and the minimum wind pressure coefficient for the cladding were analyzed and the experimental wind pressure coefficient were compared with the current wind load standards, KBC2016 and AIJ-RLB(2015). The experimental value and the reference value of the enclosed roof were very similar and showed possibility of application, but opened roof case was found that the reference value was underestimated.

• Wind and Structures
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• v.13 no.6
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• pp.499-517
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• 2010

Advances in structural materials and construction methods have resulted in flexible and light tall buildings, making an assessment of structural safety during strong wind and serviceability/habitability during comparable medium/weak wind important design criteria. So far, lots of studies on suppressing the wind-induced responses have been carried out for tall buildings with aerodynamic modification. Most of the studies on aerodynamic modification have forced on the corner modification, while the studies on taper and set-back are limited. Changes of sectional shape through taper and set-back can modify the flow pattern around the models, encouraging more 3-dimensionalities, which results in reducing the wind-induced excitations. This paper discusses the characteristics of overturning moments and wind-induced responses of the tall buildings with height variations. The reduction of mean along-wind and fluctuating across-wind overturning moments are apparent in the suburban area than in urban area. A series of the response analyses, the rms displacement responses of the tall buildings with height variations are reduced greatly, while the rms acceleration responses are not necessarily reduced, showing dependences on wind direction.

• Wind and Structures
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• v.10 no.2
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• pp.99-119
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• 2007

Estimations of wind flow over terrain are often needed for applications such as pollutant dispersion, transport safety or wind farm location. Whilst field studies offer very detailed information regarding the wind potential over a small region, the cost of instrumenting a natural fetch alone is prohibitive. Wind tunnels offer one alternative although wind tunnel simulations can suffer from scale effects and high costs as well. Computational Fluid Dynamics (CFD) offers a second alternative which is increasingly seen as a viable one by wind engineers. There are two issues associated with CFD however, that of accuracy of the predictions and set-up and simulation times. This paper aims to address the two issues by demonstrating, by way of an investigation of wind potential for the Askervein Hill, that a good level of accuracy can be obtained with CFD (10% for the speed up ratio) and that it is possible to automate the simulations in order to compute a full wind rose efficiently. The paper shows how a combination of script and session files can be written to drive and automate CFD simulations based on commercial software. It proposes a general methodology for the automation of CFD applied to the computation of wind flow over a region of interest.

• Journal of the Korean Solar Energy Society
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• v.30 no.2
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• pp.46-53
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• 2010

In this paper the feasibility of wind power forecasting from MOS(Model Output Statistics) was evaluated at Gosan area in Jeju during February to Octoberin 2008. The observed wind data from wind turbine was compared with 24 hours and 48 hours forecasting wind data from MOS predicting. Coefficient of determination of measured wind speed from wind turbine and 24 hours forecasting from MOS was around 0.53 and 48 hours was around 0.30. These determination factors were increased to 0.65 from 0.53 and 0.35 from 0.30, respectively, when it comes to the prevailing wind direction($300^{\circ}\sim60^{\circ}$). Wind power forecasting ratio in 24 hours of MOS showed a value of 0.81 within 70% confidence interval and it also showed 0.65 in 80% confidence interval. It is suggested that the additional study of weather conditions be carried out when large error happened in MOS forecasting.

• Wind and Structures
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• v.12 no.4
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• pp.299-312
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• 2009

It has long been studied about the flow around bluff bodies, but the effect of aspect ratio on the sharp-edged bodies in thick turbulent boundary layers is still argued. The author investigates the flow characteristics around a series of rectangular bodies ($40^d{\times}80^w{\times}80^h$, $80^d{\times}80^w{\times}80^h$ and $160^d{\times}80^w{\times}80^h$ in mm) placed in a deep turbulent boundary layer. The study is aiming to identify the extant Reynolds number independence of the rectangular bodies and furthermore understand the surface pressure distribution around the bodies such as the suction pressure in the leading edge, when the shape of bodies is changed, responsible for producing extreme suction pressures around the bluff bodies. The experiments are carried out at three different Reynolds numbers, based on the velocity U at the body height h, of 24,000, 46,000 and 67,000, and large enough that the mean boundary layer flow is effectively Reynolds number independent. The experiment includes wind tunnel work with the velocity and surface pressure measurements. The results show that the generation of the deep turbulent boundary layer in the wind tunnel and the surface pressure around the bodies were all independent of Reynolds number and the longitudinal length, but highly dependent of the transverse width.

• Journal of Korean Association for Spatial Structures
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• v.5 no.4 s.18
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• pp.101-108
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• 2005

The investigations for mitigating wind-induced excitations of tall buildings have been carried out. The aerodynamic modification of a building shape changing the cross-section with height through tapering, which alters the flow pattern around the building, could reduce wind induced excitations of tall buildings. The fart that a tapered tall building might spread the vortex-shedding over a broad range of frequencies makes more effective for reducing acrosswind responses has been established. In this paper, to investigate the tapering effect for reducing wind-induced responses of a tapered tall building, high-frequency force-balance test was conducted. The six types of building models which have different taper ratio of 2.5%, 5%, 7.5%, 10%, 15% and one basic building model of a square cross-section were tested under the two typical boundary layers representing suburban and urban flow environment. The effect of wind direction was also considered.

• The KSFM Journal of Fluid Machinery
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• v.17 no.6
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• pp.64-68
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• 2014

This paper is intended to provide experimental data for the design of the small VAWT(vertical axis wind turbine). Three types(lift, drag, and hybrid) of the blade of VAWT are tested with digital wind tunnel in this study. From the test, the relation of power coefficient and tip speed ratio for the blades are evaluated and compared each other depending on the blade type. Especially, the characteristics of hybrid blade which is shown to be expanded in the market without any logical data is proposed in the relation of power coefficient and tip speed ratio. It is shown that the hybrid blade can be used to make higher starting torque with trade off of degradation of power coefficient.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.3
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• pp.219-225
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• 1981

Strong wind of 6.5m/s from electric fan was applied to rice at heading stage to find out the nature of wind damage to panicle. Damaged panicles caused by typhoon were sampled out of field to measure the yield and milling components. Wind-treated glumes were developed into two forms, fertile and sterile, and each of them showed all degree of glume discoloration. The number of fertile grains were higher than sterile grains in a damaged panicle. Averagesdegree of glume discoloration was higher in not flowered glume than in flowered glume. The more recently flowered glumes resulted the higher degree of discoloration among flowered glume. The percent of sterile grain to total number of grains was the highest at stage of just flowering. The glume discoloration representing wind damage at heading state advanced in degree in ten days after treatment compared to that just after treatment. Grain length and grain width were decreased with the increased degree of glume discoloration, while grain thickness was not changed greatly. Chalkiness was a little higher in damaged grain than in normal grain without definite trends by degree of discoloration. Ripening ratio, 1000 grain weight and yield decreased with increased degree of glume discoloration in damaged panicle by typhoon. Decreasing order in yield was white rice, rough rice and brown rice. Ratio of brown rice to rough rice increased, white rice to brown rice decreased, and milling recovery was not changed greatly with increased degree of 히ume discoloration.

• Wind and Structures
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• v.31 no.3
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• pp.255-267
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• 2020

A systematic set of low-speed wind tunnel experiments was performed at Re = 6.5×10⁴ and 1.1×10⁵ to study the mean wind loading experienced by surface-mounted finite-height square prisms for different aspect ratios, incidence angles, and boundary layer thicknesses. The aspect ratio of the prism was varied from AR = 1 to 11 in small increments and the incidence angle was changed from α = 0° to 45° in increments of 1°. Two different boundary layer thicknesses were used: a thin boundary layer with δ/D = 0.8 and a thick boundary layer with δ/D = 2.0-2.2. The mean drag and lift coefficients were strong functions of AR, α, and δ/D, while the Strouhal number was mostly influenced by α. The critical incidence angle, at which the prism experiences minimum drag, maximum lift, and highest vortex shedding frequency, increased with AR, converged to a value of α_c = 18° ± 2° once AR was sufficiently high, and was relatively insensitive to changes in δ/D. A local maximum value of mean drag coefficient was identified for higher-AR prisms at low α. The overall behaviour of the force coefficients and Strouhal number with AR suggests the possibility of three flow regimes.

• Wind and Structures
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• v.14 no.5
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• pp.449-463
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• 2011

Drag forces on a rectangular louvered panel, both as a free-standing structure and as a component in a generic low-rise building model, were obtained in a wind tunnel study. When tested in a building model, the porosity ratio of the wall opposite the louvered panel was varied to investigate its effect on the loading of the louvered panel. Both mean and pseudo-steady drag coefficients were obtained. Comparisons with the provisions for porous walls in contemporary loading standards indicate that for some opposite wall porosity ratios, the standards specify significantly different wind loads (larger and smaller) than obtained from this wind tunnel study.