• 제목/요약/키워드: wind tunnel testing

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Will CFD ever Replace Wind Tunnels for Building Wind Simulations?

  • Phillips, Duncan A.;Soligo, Michael J.
    • 국제초고층학회논문집
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    • 제8권2호
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    • pp.107-116
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    • 2019
  • The use of computational fluid dynamics (CFD) is becoming an increasingly popular means to model wind flows in and around buildings. The first published application of CFD to both indoor and outdoor building airflows was in the 1970's. Since then, CFD usage has expanded to include different aspects of building design. Wind tunnel testing (WTT) on buildings for wind loads goes back as far as 1908. Gustave Eiffel built a pair of wind tunnels in 1908 and 1912. Using these he published wind loads on an aircraft hangar in 1919 as cited in Hoerner (1965 - page 74). The second of these wind tunnels is still in use today for tests including building design ($Damljanovi{\acute{c}}$, 2012). The Empire State Building was tested in 1933 in smooth flow - see Baskaran (1993). The World Trade Center Twin Towers in New York City were wind tunnel tested in the mid-sixties for both wind loads, at Colorado State University (CSU) and the [US] National Physical Laboratory (NPL), as well as pedestrian level winds (PLW) at the University of Western Ontario (UWO) - Baskaran (1993). Since then, the understanding of the planetary boundary layer, recognition of the structures of turbulent wakes, instrumentation, methodologies and analysis have been continuously refined. There is a drive to replace WTT with computational methods, with the rationale that CFD is quicker, less expensive and gives more information and control to the architects. However, there is little information available to building owners and architects on the limitations of CFD for flows around buildings and communities. Hence building owners, developers, engineers and architects are not aware of the risks they incur by using CFD for different studies, traditionally conducted using wind tunnels. This paper will explain what needs to happen for CFD to replace wind tunnels. Ultimately, we anticipate the reader will come to the same conclusion that we have drawn: both WTT and CFD will continue to play important roles in building and infrastructure design. The most pressing challenge for the design and engineering community is to understand the strengths and limitations of each tool so that they can leverage and exploit the benefits that each offers while adhering to our moral and professional obligation to hold paramount the safety, health, and welfare of the public.

Assessment of vertical wind loads on lattice framework with application to thunderstorm winds

  • Mara, T.G.;Galsworthy, J.K.;Savory, E.
    • Wind and Structures
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    • 제13권5호
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    • pp.413-431
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    • 2010
  • The focus of this article is on the assessment of vertical wind vector components and their aerodynamic impact on lattice framework, specifically two distinct sections of a guyed transmission tower. Thunderstorm winds, notably very localized events such as convective downdrafts (including downbursts) and tornadoes, result in a different load on a tower's structural system in terms of magnitude and spatial distribution when compared to horizontal synoptic winds. Findings of previous model-scale experiments are outlined and their results considered for the development of a testing rig that allows for rotation about multiple body axes through a series of wind tunnel tests. Experimental results for the wind loads on two unique experimental models are presented and the difference in behaviour discussed. For a model cross arm with a solidity ratio of approximately 30%, the drag load was increased by 14% when at a pitch angle of $20^{\circ}$. Although the effects of rotation about the vertical body axis, or the traditional 'angle of attack', are recognized by design codes as being significant, provisions for vertical winds are absent from each set of wind loading specifications examined. The inclusion of a factor to relate winds with a vertical component to the horizontal speed is evaluated as a vertical wind factor applicable to load calculations. Member complexity and asymmetric geometry often complicate the use of lattice wind loading provisions, which is a challenge that extends to future studies and codification. Nevertheless, the present work is intended to establish a basis for such studies.

Wind-induced response of structurally coupled twin tall buildings

  • Lim, Juntack;Bienkiewicz, Bogusz
    • Wind and Structures
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    • 제10권4호
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    • pp.383-398
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    • 2007
  • The paper describes a study of the effects of structural coupling on the wind-induced response of twin tall buildings connected by a skybridge. Development of a dual high-frequency force balance used in wind tunnel investigation and background information on the methodology employed in analysis are presented. Comparisons of the wind-induced building response (rooftop acceleration) of structurally coupled and uncoupled twin buildings are provided and the influence of structural coupling is assessed. It is found that the adverse aerodynamic interference effects caused by close proximity of the buildings can be significantly reduced by the coupling. Neglecting of such interactions may lead to excessively conservative estimates of the wind-induced response of the buildings. The presented findings suggest that structural coupling should be included in wind-resistant design of twin tall buildings.

Optimal wind-induced load combinations for structural design of tall buildings

  • Chan, C.M.;Ding, F.;Tse, K.T.;Huang, M.F.;Shum, K.M.;Kwok, K.C.S.
    • Wind and Structures
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    • 제29권5호
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    • pp.323-337
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    • 2019
  • Wind tunnel testing technique has been established as a powerful experimental method for predicting wind-induced loads on high-rise buildings. Accurate assessment of the design wind load combinations for tall buildings on the basis of wind tunnel tests is an extremely important and complicated issue. The traditional design practice for determining wind load combinations relies partly on subjective judgments and lacks a systematic and reliable method of evaluating critical load cases. This paper presents a novel optimization-based framework for determining wind tunnel derived load cases for the structural design of wind sensitive tall buildings. The peak factor is used to predict the expected maximum resultant responses from the correlated three-dimensional wind loads measured at each wind angle. An optimized convex hull is further developed to serve as the design envelope in which the peak values of the resultant responses at any azimuth angle are enclosed to represent the critical wind load cases. Furthermore, the appropriate number of load cases used for design purposes can be predicted based on a set of Pareto solutions. One 30-story building example is used to illustrate the effectiveness and practical application of the proposed optimization-based technique for the evaluation of peak resultant wind-induced load cases.

고속철도차량용 팬터그래프의 공력특성 평가를 위한 실모형 풍동시험 (A Real-scale Wind Tunnel Testing on a Pantograph for High-speed Train to Assess the Aerodynamic Characteristics)

  • 권혁빈;조용현;이기원;김기남
    • 한국철도학회논문집
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    • 제12권5호
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    • pp.732-737
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    • 2009
  • 본 연구에서는 고속주행 시 팬터그래프에 가해지는 공기역학적 특성을 평가하기 위하여 고속철도차량용 실모형 팬터그래프에 대한 풍동시험을 수행하였다. 시험에 사용된 풍동은 공군사관학교의 중형아음속풍동으로서 폭 3.5m $\times$ 높이 2.45m $\times$ 길이 8.8m의 시험부를 가지며, 시험 모형은 하단의 차체부착용 브라켓에서 50cm의 수직 스트럿을 통해 풍동 바닥면에 지지되어 자유류가 시험부 바닥을 지나면서 성장하는 경계층의 영향을 제거하였다. 시험모델은 표준높이와 최소높이 및 풍동의 시험부를 고려한 최대높이에 대하여 정상주행방향 및 역방향 시의 조건을 바꾸어가며 수행되었다. 각각의 조건에 대해서 팬터그래프가 가선에 미치는 압상력을 측정하였으며, 시험 조건에 따른 압상력의 변화에 대하여 분석하였다.

$25cm{\times}20cm$ 초음속 풍동 개발 및 시험 평가 (Development and Operating Test of the Supersonic Wind Tunnel with $25cm{\times}20cm$ Test Section)

  • 김세환;박지현;이승복;정인석;이형진
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2011년도 제37회 추계학술대회논문집
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    • pp.777-780
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    • 2011
  • 초음속 풍동은 고속으로 운용되는 비행체나 유도무기의 개발에 있어 시험체 주위에서 나타나는 공기역학적 현상을 연구하고 특성을 대표하는 물리량을 측정하기 위해 주로 사용되는 지상시험 장비이다. 본 연구에서는 연구팀에서 보유하고 있는 소형 초음속 풍동이 갖는 시험 모델 크기의 제약을 완화하고자 $250mm{\times}200mm$ 의 시험부를 갖는 초음속 풍동을 설계하고 제작된 풍동의 성능 평가를 수행하였다. 제작된 풍동의 시험 마하수는 2.5이며 시험부에서 균일한 유동을 얻을 수 있도록 경계층 보정을 수행하여 노즐의 형상을 결정하였다.

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풍동시험에서 반응면을 이용한 내부 항력 및 벽면 효과의 효율적 보정방안 연구 (A Study on Effective Correction of Internal Drag and Wall Interference Using Response Surface in Wind Tunnel Test)

  • 김준모;이영빈
    • 한국군사과학기술학회지
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    • 제22권5호
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    • pp.637-643
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    • 2019
  • Wind tunnel testing for flow-through model is necessary for performance prediction of an aircraft with air-breathing jet engine. Internal drag correction and wall correction are performed to acquire preciser wind tunnel test data. Many test runs are generally required to correct internal drag and wall interference in wind tunnel test. In this study we investigated more effective correction schemes using the response surface method. Even though the number of tests required for these schemes was much smaller than that for conventional methods, the differences between corrections using these schemes and conventional methods were similar level with the uncertainty of measurement except for the data near the boundaries.

Wind loads on a moving vehicle-bridge deck system by wind-tunnel model test

  • Li, Yongle;Hu, Peng;Xu, You-Lin;Zhang, Mingjin;Liao, Haili
    • Wind and Structures
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    • 제19권2호
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    • pp.145-167
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    • 2014
  • Wind-vehicle-bridge (WVB) interaction can be regarded as a coupled vibration system. Aerodynamic forces and moment on vehicles and bridge decks play an important role in the vibration analysis of the coupled WVB system. High-speed vehicle motion has certain effects on the aerodynamic characteristics of a vehicle-bridge system under crosswinds, but it is not taken into account in most previous studies. In this study, a new testing system with a moving vehicle model was developed to directly measure the aerodynamic forces and moment on the vehicle and bridge deck when the vehicle model moved on the bridge deck under crosswinds in a large wind tunnel. The testing system, with a total length of 18.0 m, consisted of three main parts: vehicle-bridge model system, motion system and signal measuring system. The wind speed, vehicle speed, test objects and relative position of the vehicle to the bridge deck could be easily altered for different test cases. The aerodynamic forces and moment on the moving vehicle and bridge deck were measured utilizing the new testing system. The effects of the vehicle speed, wind yaw angle, rail track position and vehicle type on the aerodynamic characteristics of the vehicle and bridge deck were investigated. In addition, a data processing method was proposed according to the characteristics of the dynamic testing signals to determine the variations of aerodynamic forces and moment on the moving vehicle and bridge deck. Three-car and single-car models were employed as the moving rail vehicle model and road vehicle model, respectively. The results indicate that the drag and lift coefficients of the vehicle tend to increase with the increase of the vehicle speed and the decrease of the resultant wind yaw angle and that the vehicle speed has more significant effect on the aerodynamic coefficients of the single-car model than on those of the three-car model. This study also reveals that the aerodynamic coefficients of the vehicle and bridge deck are strongly influenced by the rail track positions, while the aerodynamic coefficients of the bridge deck are insensitive to the vehicle speed or resultant wind yaw angle.

Flutter suppression of long-span suspension bridge with truss girder

  • Wang, Kai;Liao, Haili;Li, Mingshui
    • Wind and Structures
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    • 제23권5호
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    • pp.405-420
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    • 2016
  • Section model wind tunnel test is currently the main technique to investigate the flutter performance of long-span bridges. Further study about applying the wind tunnel test results to the aerodynamic optimization is still needed. Systematical parameters and test principle of the bridge section model are determined by using three long-span steel truss suspension bridges. The flutter critical wind at different attack angles is obtained through section model flutter test. Under the most unfavorable working condition, tests to investigate the effects that upper central stabilized plate, lower central stabilized plate and horizontal stabilized plate have on the flutter performance of the main beam were conducted. According to the test results, the optimal aerodynamic measure was chosen to meet the requirements of the bridge wind resistance in consideration of safety, economy and aesthetics. At last the credibility of the results is confirmed by full bridge aerodynamic elastic model test. That the flutter reduced wind speed of long-span steel truss suspension bridges stays approximately between 4 to 5 is concluded as a reference for the investigation of the flutter performance of future similar steel truss girder suspension bridges.

Development of wind vortex shedding coefficients for a multisided cylinder structure

  • Chang, Byungik;Neill, Michael;Issa, Roy;Miller, Aaron
    • Wind and Structures
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    • 제18권2호
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    • pp.181-194
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    • 2014
  • A major problem with high-mast light poles is the effects that wind vortex shedding can have on the pole itself because of the lock-in phenomenon. It is desired that the coefficients in the AASHTO Standard Specifications ($5^{th}$ edition) for Structural Supports for Highway Signs, Luminaries, and Traffic Signals be analyzed and refined. This is for the belief that the span of the shapes of poles for which the coefficients are used is much too broad and a specific coefficient for each different shape is desired. The primary objective of this study is to develop wind vortex shedding coefficient for a multisided shape. To do that, an octagonal shape was used as the main focus since octagonal cross sectioned high-mast light poles are one of the most common shapes in service. For the needed data, many wind parameters, such as the static drag coefficient, the slope of aerodynamic lift coefficient, Strouhal number, the lock-in range of wind velocities producing vibrations, and variation of amplitude of vortex-induced vibration with Scruton number are needed. From wind tunnel experiments, aerodynamic parameters were obtained for an octagonal shape structure. Even though aerodynamic coefficients are known from past test results, they need to be refined by conducting further wind tunnel tests.