• Wind and Structures
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• 제25권1호
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• pp.1-24
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• 2017

This paper presents a 1:25 multi-freedom aero-elastic model for a high lighting pole at the Zhoushan stadium. To validate the similarity characteristics of the model, a free vibration test was performed before the formal test. Beat phenomenon was found and eliminated by synthesis of vibration in the X and Y directions, and the damping ratio of the model was identified by the free decay method. The dynamic characteristics of the model were examined and compared with the real structure; the similarity results were favorable. From the test results, the major along-wind dynamic response was the first vibration component. The along-wind wind vibration coefficient was calculated by the China code and Eurocode. When the peak factor equaled 3.5, the coefficient calculated by the China code was close to the experimental result while Eurocode had a slight overestimation of the coefficient. The wind vibration coefficient during typhoon flow was analyzed, and a magnification factor was suggested in typhoon-prone areas. By analyzing the power spectrum of the dynamic cross-wind base shear force, it was found that a second-order vortex-excited resonance existed. The cross-wind response in the test was smaller than Eurocode estimation. The aerodynamic damping ratio was calculated by random decrement technique and the results showed that aerodynamic damping ratios were mostly positive at the design wind speed, which means that the wind-induced galloping phenomenon is predicted not to occur at design wind speeds.

• 한국항공우주학회지
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• 제43권5호
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• pp.422-431
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• 2015

풍동실험에 적용하는 실험계획법을 연구하기 위한 선행 연구로써 KF-16의 정적 공력 데이터베이스를 구축하는 풍동 실험을 수행하였다. 본 실험에서 사용된 기체는 KF-16의 1/33 scale의 모델이며 수평 꼬리날개와 플래퍼론, 방향타를 모두 구현하였다. 크게 실험은 수평 꼬리날개의 유무에 따른 공력 특성 변화를 보기 위한 실험과 플랩, 플래퍼론, 방향타, 그리고 수평 꼬리날개의 변위각에 따른 공력특성 변화를 알아보기 위한 실험을 수행하였다. 실험 수행 후에는 각 실험들에 대해서 6가지 공력계수 그래프를 분석하고 반응 표면을 생성하면서 조종면의 변화가 각각 어떤 공력 특성에 큰 영향을 미치는지 알아보았다.

• Asian Journal of Atmospheric Environment
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• 제2권1호
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• pp.1-13
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• 2008

A numerical simulation method has been developed to predict atmospheric flow and stack gas diffusion using a calculation domain of several km around a stack under complex terrain conditions containing buildings. The turbulence closure technique using a modified k-$\varepsilon$-type model under a non hydrostatic assumption was used for the flow calculation, and some of the calculation grids near the ground were treated as buildings using a terrain-following coordinate system. Stack gas diffusion was predicted using the Lagrangian particle model, that is, the stack gas was represented by the trajectories of released particles. The numerical model was applied separately to the flow and stack gas diffusion around a cubical building and to a two-dimensional ridge in this study, before being applied to an actual terrain containing buildings in our next study. The calculated flow and stack gas diffusion results were compared with those obtained by wind tunnel experiments, and the features of flow and stack gas diffusion, such as the increase in turbulent kinetic energy and the plume spreads of the stack gas behind the building and ridge, were reproduced by both calculations and wind tunnel experiments. Furthermore, the calculated profiles of the mean velocity, turbulent kinetic energy and concentration of the stack gas around the cubical building and the ridge showed good agreement with those of wind tunnel experiments.

• 국제초고층학회논문집
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• 제11권3호
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• pp.145-156
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• 2022

Application examples of computational fluid dynamics (CFD) in the planning stage of high-rise buildings are introduced. First, we introduce examples of applications in the environmental field. The pedestrian wind environment was one of the earliest practical examples of CFD. CFD was also employed to validate the heat island mitigation measures proposed as part of the new construction plan. Second, application examples of wind-force evaluations are introduced. Prediction examples are presented for the peak wind pressure around a complex-shaped building and the wind force evaluation for a base-isolated building. The results prove that the results of the proper execution of CFD are equivalent to those of the wind tunnel experiment. As examples of CFD applications of other issues related to high-rise building planning, we introduce snow accretion on outer walls and high-temperature exhaust from emergency generators. Finally, the future prospects for the use of CFD are discussed.

• Wind and Structures
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• 제2권3호
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• pp.173-187
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• 1999

The flow around a structure has been an important subject in wind engineering research. There are various kinds of unstable aerodynamic phenomena with regard to a bluff body. In order to understand the physical mechanism of aerodynamic and aeroelastic instability of a bluff body, the relations between the flow around structures and the motion of body with various section shapes should be investigated. Based on a series of wind tunnel tests, this paper addresses the aerodynamic stability of square cylinder with various corner cuts and attack angles in the uniform flow. The test results show that the models with corner cut produced generally better behaviour for the galloping phenomenon than the original section. However, the corner cut method can not prevent the occurrence of the vortex-induced vibration(VIV). It is also shown that as the attack angle changes, the optimum size of corner cut changes also. This means that any one specific size of corner cut which shows the best aerodynamic behaviour throughout all the cases of attack angles does not exist. This paper presents an intensive study on obtaining the optimum size of corner cut for the stabilization of aerodynamic behaviour of cylinders.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2923-2928
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• 2007

The study of model for velocity and turbulence within the urban canopy was carried out. To evaluate existing urban model we conducted wind tunnel experiment and large-eddy simulation (LES). Mean velocity profile and turbulence are measured within simple three different obstacle arrays. To obtain supplemental data and to verify morphological model large-eddy simulation was performed. Several methods have been used to achieve embodying the flow field in urban area. Recently, morphological method obtaining flow parameters from the statistical or physical representation of obstacle elements is a arising method. It was found that all morphological model, evaluated in this study, over predict the friction velocity, most sensitive one among the flow parameters. Velocity and turbulence in the urban canopy layer were improved by the correction using 'true' friction velocity.

• International Journal of Fluid Machinery and Systems
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• 제9권2호
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• pp.129-136
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• 2016

An experimental investigation was carried out to improve the performance of a counter-rotating type horizontal-axis tidal stream power unit. Front and rear blades were designed separately based on modified blade element momentum (BEM) theory, and their performances at different conditions of blade tip speed ratio were measured in a wind tunnel. Three different groups of blades were designed successively, and the results showed that Group3 possessed the highest power coefficient of 0.44 and was the most satisfactory model. This experiment shows that properly increasing diameter and reducing chord length will benefit the performance of the blade.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.586-589
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• 2009

일본 JAXA가 보유하고 있는 Blow down 방식의 초음속 풍동 "RAMSYS"를 이용하여 스크램제트 엔진 연소기의 연소시험을 수행하였다. 시험결과로 Cavity가 없는 경우보다 Cavity를 장착한 경우에 연소압력이 높게 나타나는 것으로 확인되었으며 본 연구를 통하여 새롭게 적용한 zigzag cavity는 가장 높은 연소압력을 보여 스크램제트엔진의 안정적인 운영에 기여할 것으로 기대된다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.17-20
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• 2010

An aerial target system is used for the purpose of experimental test and fire training of missile that newly developed and in mass production. Since the target drones of aerial target systems are monopolized by several major countries so that they are selling at a high price. In this paper, we present the CFD simulation results on a new target drone that Kyungan co. ltd is developing with their own technologies. The presented CFD simulation was conducted in the same conditions of a wind tunnel tests and we could obtain the simulation results of the lift and drag values were in errors by less than 15 percent compared to the experiment. The simulation results were used to determine the modified shapes of new prototype target drone that could fly safely.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1819-1828
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• 2004

The purpose of this paper is to investigate the effects of slits and swirl vanes on the turbulence augmentation in the flow fields of a gun-type gas burner using an X-type hot-wire probe. The gun-type gas burner adopted in this study is composed of eight slits and swirl vanes located on the surface of an inclined baffle plate. Experiment was carried out at a flow rate of 450 ι/min in burner model installed in the test section of subsonic wind tunnel. Swirl vanes playa role diffusing main flow more remarkably toward the radial direction than axial one, but slits show a reverse feature. Consequently, both slits and swirl vanes remarkably increase turbulence intensity in the whole range of a gun-type gas burner with a cone-type baffle plate.