• Wind and Structures
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• 제27권2호
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• pp.101-109
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• 2018

Wall jet flow exists widely in engineering applications, including the simulation of thunderstorm downburst outflows, and has been investigated extensively by both experimental and numerical methods. Most previous studies focused on the scaling laws and self-similarity, while the effect of lip thickness and external stream height on mean velocity has not been examined in detail. The present work is a numerical study, using steady Reynolds-Averaged Navier Stokes (RANS) simulations at a Reynolds number of $3.5{\times}10^4$, of a turbulent plane wall jet with an external stream to investigate the influence of the wall jet domain on downstream development of the flow. The comparisons of flow characteristics simulated by the Reynolds stress turbulence model closure (Stress-omega, SWRSM) and experimental results indicate that this model may be considered reasonable for simulating the wall jet. The confined wall jet is further analyzed in a parametric study, with the results compared to the experimental data. The results indicate that the height and the width of the wind tunnel and the lip thickness of the jet nozzle have a great effect on the wall jet development. The top plate of the tunnel does not confine the development of the wall jet within 200b of the nozzle when the height of the tunnel is more than 40b (b is the height of jet nozzle). The features of the centerline flow in the mid plane of the 3D numerical model are close to those of the 2D simulated plane wall jet when the width of the tunnel is more than 20b.

• Wind and Structures
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• 제19권6호
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• pp.603-621
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• 2014

Past high speed wind events have exposed the vulnerability of the roof systems of existing light-framed wood structures to uplift loading, contributing greatly to economic and human loss. This paper further investigates the behaviour of light-framed wood structures under the uplift loading of a realistic pressure distribution. A three-dimensional finite-element model is first developed to capture the behaviour of a recently completed full-scale experiment. After describing the components used to develop the numerical model, a comparison between the numerical prediction and experimental results in terms of the deflected shape at the roof-to-wall connections is presented to gain confidence in the numerical model. The model is then used to analyze the behaviour of the truss system under realistic and equivalent uniform pressure distributions and to perform an assessment of the use of the tributary area method to calculate the withdrawal force acting on the roof-to-wall connections.

• Wind and Structures
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• 제11권5호
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• pp.361-376
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• 2008

This paper considers internal pressure fluctuations for a range of building volumes and dominant wall opening areas. The study recognizes that the air flow in and out of the dominant opening in the envelope generates Helmholtz resonance, which can amplify the internal pressure fluctuations compared to the external pressure, at the opening. Numerical methods were used to estimate fluctuating standard deviation and peak (i.e. design) internal pressures from full-scale measured external pressures. The ratios of standard deviation and peak internal pressures to the external pressures at a dominant windward wall opening of area, AW are presented in terms of the non-dimensional opening size to volume parameter, $S^*=(a_s/\bar{U}_h)^2(A_W^{3/2}/V_{Ie})$ where $a_s$ is the speed of sound, $\bar{U}_h$ is the mean wind speed at the top of the building and $V_{Ie}$ is the effective internal volume. The standard deviation of internal pressure exceeds the external pressures at the opening, for $S^*$ greater than about 0.75, showing increasing amplification with increasing $S^*$. The peak internal pressure can be expected to exceed the peak external pressure at the opening by 10% to 50%, for $S^*$ greater than about 5. A dominant leeward wall opening also produces similar fluctuating internal pressure characteristics.

• 한국항공우주학회지
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• 제33권8호
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• pp.42-49
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• 2005

아음속풍동 폐쇄형 시험부의 벽면효과 보정을 위한 새로운 blockage 보정 기법을 개발하였다. 개발된 보정 기법은 실속항력계수와 separation blockage의 비선형 관계를 이용하여 선형 양력곡선 기울기 영역에서 후실속 영역까지 실시간으로 보정이 가능하게 하였다. 본 연구에서 제시한 방법은 bluff body 시험 결과를 사용하는 고전적 방법과 벽면압력측정 방법과 비교하여 그 타당성을 검증하였다. 그 결과 본 연구에서 제시한 보정 방법은 실속 및 후실속 영역에서 bluff body 방법보다 우수한 보정 결과를 보이며 벽면압력측정 방법과 같은 정확도로 보정됨을 확인할 수 있었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 추계 학술논문 발표대회
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• pp.197-198
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• 2011

Most of buildings' exterior walls are curtain wall systems and in the respect, the cleaning robot system is the main research item for cleaning and maintenance of them. We have structurely analysed the cases to review on the structural stability of the mullion members where the cleaning robot is attached. The result is showing that the largest stress is formed by the basic wind speed, which is specified in Korean Building Code-Structural.

• 한국터널지하공간학회 논문집
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• 제20권1호
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• pp.39-53
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• 2018

일반적으로 터널 내 총환기저항계수는 입출구 손실계수, 벽면마찰계수 그리고 급격한 확대나 축소단면 등에 의해 발생하는 부차적 손실계수의 총합으로 구성된다. 개통 전 터널의 경우는 가동 중인 환기팬을 중단하게 되면, 터널 내 풍속은 총환기저항력에 의해 감소하는 현상이 나타난다. 즉, 속도감쇄법은 개통 전 터널에서 비교적 안정적이면서도 손쉽게 터널 내 벽면마찰계수를 추정하는 방법이다. 그러나 기존의 선행연구에서 환기팬의 가동을 중단 후 수렴되는 풍속이 음수일 경우는 속도감쇄법에 따른 벽면마찰계수의 추정이 곤란한 특성이 있다. 반면 교통환기력이 작용하는 공용 중인 터널에서는 좀더 복잡한 과정을 거치지만, 합리적인 벽면마찰계수를 추정할 수 있다. 본 연구에서는 교통환기력의 측정변수를 최소화할 수 있는 방법을 제안하였고, 공용 중 터널에 적용할 수 있는 방법을 고찰하였다. 또한 환기팬 정지 후 터널 내 풍속이 감소하는 동안에 외부 자연풍의 급격한 변화가 발생하여도 교통환기력이 일정할 경우에 대하여, 교통환기력의 증분을 계산할 수 있는 방법과 터널 내 벽면마찰계수를 추정할 수 있도록 동적 시뮬레이션이 가능한 프로그램 로직을 개발하였다.

• Wind and Structures
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• 제34권2호
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• pp.231-257
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• 2022

Transmission lines systems are important components of the electrical power infrastructure. However, these systems are vulnerable to damage from high wind events such as hurricanes. This study presents the results from a 1:50 scale aeroelastic model of a multi-span transmission lines system subjected to simulated hurricane winds. The transmission lines system considered in this study consists of three lattice towers, four spans of conductors and two end-frames. The aeroelastic tests were conducted at the NSF NHERI Wall of Wind Experimental Facility (WOW EF) at the Florida International University (FIU). A horizontal distortion scaling technique was used in order to fit the entire model on the WOW turntable. The system was tested at various wind speeds ranging from 35 m/s to 78 m/s (equivalent full-scale speeds) for varying wind directions. A system identification (SID) technique was used to evaluate experimental-based along-wind aerodynamic damping coefficients and compare with their theoretical counterparts. Comparisons were done for two aeroelastic models: (i) a self-supported lattice tower, and (ii) a multi-span transmission lines system. A buffeting analysis was conducted to estimate the response of the conductors and compare it to measured experimental values. The responses of the single lattice tower and the multi-span transmission lines system were compared. The coupling effects seem to drastically change the aerodynamic damping of the system, compared to the single lattice tower case. The estimation of the drag forces on the conductors are in good agreement with their experimental counterparts. The incorporation of the change in turbulence intensity along the height of the towers appears to better estimate the response of the transmission tower, in comparison with previous methods which assumed constant turbulence intensity. Dynamic amplification factors and gust effect factors were computed, and comparisons were made with code specific values. The resonance contribution is shown to reach a maximum of 18% and 30% of the peak response of the stand-alone tower and entire system, respectively.

• 한국전산구조공학회논문집
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• 제29권2호
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• pp.131-140
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• 2016

최근 강풍으로 인한 옥외광고물의 파손 및 추락으로 인해 불특정 다수에게 인적 및 물적 피해를 야기하고 있다. 옥외광고물은 사유시설과 공공시설물의 성격을 모두 갖기 때문에 옥외광물로 인한 피해를 저감하는 것은 개인의 노력뿐 아니라 제도 및 규정을 통해서도 이루어져야한다. 이러한 피해는 강풍에 취약한 옥외광고물의 내풍설계 기준의 미비가 가장 큰 요인으로 인식되고 있어 본 연구에서는 옥외광고물의 내풍설계 표준을 제시하였다. 이를 위해 풍속에 영향을 주는 옥외광고물 설치위치의 주변 풍환경이나 높이, 설치위치 등 풍속과 관련한 요소를 반영하였으며, 건축구조기준 2015(안)의 기본풍속도와 풍속보정 절차에 의한 풍하중 산정 과정을 제시하였다. 이 과정에서 공학적 판단이 요구되는 옥외광고물 설치위치 주변의 지표 조도구분 및 지형계수 평가에 대해 정략적으로 적용할 수 있는 기준을 제시하였다. 또한 비전문가 관점에서 적용하기 용이하도록 가능한 단순화된 정량화 절차를 제시하였다.

• Wind and Structures
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• 제9권6호
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• pp.419-440
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• 2006

This article synthesizes the literature on the meteorology, experimental simulation, and wind engineering ramifications of intense downburst outflows. A novel design of a large-scale test facility and experimental evidence of its validity are presented. A two-dimensional slot jet is used to simulate only the outflow region of a downburst. Profiles of mean velocity and turbulence quantities are acquired using hot-wire anemometry. Comparison with the literature provides empirical evidence that supports the current approach. A geometric analysis considers the validity of applying a two-dimensional approximation for downburst wind loading of structures. This analysis is applicable to power transmission lines in particular. The slot jet concept can be implemented in a large boundary layer wind tunnel to enable large-scale laboratory experiments of thunderstorm wind loads on structures.

• 항공우주기술
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• 제7권2호
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• pp.27-30
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• 2008

풍동시험의 벽면효과 보정방법이 풍동시험 조건에서 수행된 전산해석결과에 적용되었다. 보정을 마친 양력계수는 벽면이 없는 조건에서 수행된 전산해석 결과와 잘 일치하지만 보정된 항력계수는 벽면효과가 제거된 결과와 약간의 차이를 보인다.