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RISS 인기검색어
- 검색키워드
- 주제어 : Vortex Shedding(와유출) (검색결과 4 건)
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풍응답에 효과적인 초고층건물의 기본형상에 관한 풍동실험 연구 - 건물의 지붕면 형상 변화를 중심으로 -
하영철,정영배,길용식 한국풍공학회 2002 한국풍공학회지 Vol.6 No.2
The excessive wind-induced motion of tall buildings most frequently results from vortex shedding induced across-wind oscillations. This form of excitation is most pronounced for relatively flexible, lightweight and lightly damped structure, e.g. super high-rise building. This paper discusses the effective elevation and roof shapes for mitigating the across-wind vortex shedding induced in such situations. Emphasis is on the change of the building cross section to design the building with a cutting flat roof surfaces which provide pressure equalization and tend to reduce the effectiveness of across-wind forces by reducing their magnitudes and disrupting their spatial correlation. Wind tunnel test have been carried out at Kumoh National University of Technology using rigid models for twelve kinds of a changing roof shape and three kinds of a square cylinder shape which have aspect ratio of 4, 6 and 8. The measured aerodynamic excitations and displacements for cutting roof models had been compared to those of square cylinder model with respect to the aspect ratio, the roof shape and the cutting ratio to estimate the effectiveness of cutting of roof surface for wind-induced oscillations. 강풍에 의한 고층건축물의 진동은 주로 풍직각방향의 와유출에 의하여 발생한다. 이러한 풍직각방향 진동은 비교적 유연하고, 경량이며 경감쇠를 가진 구조물(예를 들면 초고층건물)인 경우에 현저해진다. 본 연구는 풍직각 방향의 와유출을 저감시키기 위한 입면과 지붕면 형상을 통한 효과를 검토한 것이다. 그 방법으로는 풍압력을 감소시키고 와유출의 발생을 방해하기 위하여 평평한 지붕면을 절개시켜 건물의 입면 형상을 변화시켰다. 풍동실험은 형상비가 4, 6, 8이고 지붕면을 변화시킨 12종류의 강체모형과 3종류의 사각형 각주모형을 대상으로 금오공과대학교의 풍동에서 실시하였다. 실험결과로부터 지붕면 형상변화에 따른 풍진동 및 응답변위 특성을 형상비별, 지붕면 형상별, 지붕면 절개율별로 사각형 각주와 비교 분석하고 지붕면 형상 변화에 따른 풍진동 저감효과를 정량적으로 제시하였다.
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김정현(Jeong-Hyun Kim),한용운(Yong Oun Han) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In order to study turbulent structure of wake flow around the rear view side mirror of a passenger car, statistical and spectral measurements were conducted in a blow down wind tunnel with the Reynolds number of 2 × 10?. Moment property and turbulent energy in the mirror wake were measured by using hot wire anemometry and dynamic signal analyzer at 0.7d, 1.4d and 2.8d downstream (d is the height length of the mirror). Also, Laser Doppler Velocimetry was used to measure velocity in the recirculation zone behind the mirror. Mean velocity was accelerated behind tip region of the mirror housing and the recirculation zone was observed up to 1.2d downstream of the mirror. Also, peak values of fluctuation rms velocity appeared in the vicinity of the mirror wake due to remarkable vortex shedding. The corresponding skewness and flatness factor were significantly deviant from a Gaussian distribution. Spectra analysis showed that most of energy was concentrated in the low frequency and the magnitude of energy distribution was reduced with downstream. It was concluded that strong turbulent energy at the near wake was induced by considerable vortex shedding having a non-random characteristics, resulted in intermittent force around tip region of the mirror surface.
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박종규(Jong-Kyu Park),서성호(Seong-Ho Seo),부정숙(Jung-Sook Boo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This experimental study is conducted to investigate the effect of a splitter plate, which is set on the back side of a square prism in the uniform flow, Re=1.44×10⁴. The measurement of velocity vector and pressure distribution are carried out 4 cases of length in the range of 0.5ℓ to 2.0ℓ with 0.5ℓ interval and 3 cases of position at 0ℓ, 0.25ℓ, 0.5ℓ. Flow visualization is also executed by smoke-wire method to understand the mechanism of vortex fprmation. The results show the strong vortex shedding patterns and drags are decreased effectively, when the position of splitter plate is 0ℓ. and the drag reduction rate is in inverse proportion to the splitter plate length.
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