The effects of wind on people; New criteria based on wind tunnel experiments

Experiments on the effects of wind on people are described. About 40 people were involved in tests in a wind tunnel at the National Physical Laboratory. The wind tunnel was specially-adapted to produce gusty winds. The volunteers performed a number of everyday tasks at wind speeds of 4 and 8·5 m/s with and without turbulence. The steadiness and direction of walking were measured when the volunteers entered the tunnel and walked up and down. Forces on the ground were also measured. Six groups of volunteers gave subjective verbal assessments of wind conditions ranging from 4 to 12·5 m/s.From the experiments we have drawn conclusions as to what kinds of wind speed, gustiness and variation of wind speed are found to be tolerable, are found to affect performance, and are found to affect the people's balance while walking. We find people to be sensitive to variation in the wind so that previous criteria for acceptable wind speeds need to be revised downwards. New criteria are proposed to enable architects and planners to use wind speed and gustines data to predict whether wind conditions are likely to be acceptable or not.     

巨型框架刚性模型风荷载特性的风洞试验研究

给出了以矩形为基本截面形状的巨型框架结构刚性模型测压试验方法和试验内容,分析了风洞试验得到的风压值,提供了巨型框架建筑表面风压分布规律和体型系数。所得的这些结果对结构的抗风设计有较为重要的指导意义。     

Field measurement and wind tunnel simulation of hurricane wind loads on a single family dwelling

During landfall of Hurricane Ivan on the Florida ’panhandle’ in 2004, pressure time-history data were recorded on multiple pressure sensors installed on the roofs of six single-family homes. An analysis approach was developed to determine the peak negative, mean, peak positive, and standard deviation of pressure coefficients for these datasets. This paper presents a comparison of the full scale pressure coefficients from one of these homes, which experienced sustained hurricane force winds, with the results of wind tunnel experiments on a 1:50 scale model of that home. It was determined that the wind tunnel and full-scale mean and rms pressure coefficients matched very closely at almost every monitored location on the roof, while the peak negative pressure coefficients in the wind tunnel study generally underestimated the full-scale values, consistent with observations from previous full-scale/wind tunnel comparative studies. Field-measured hurricane wind loads may prove useful for evaluating existing wind load provisions. However, recommendations in that regard are premature without the analyses of multiple homes in multiple storms, performed by more than one wind tunnel facility. Future work will focus on building such a joint study.     

广州塔风荷载及风洞试验研究

广州塔总高600m,塔体外形复杂,基本周期长,对风荷载的响应比较敏感,风荷载成为结构设计的主要控制荷载。针对广州塔的特点,分两阶段进行了风工程研究,第一阶段解决外界风的输入问题,第二阶段解决结构在风荷载作用下的响应问题。风荷载及风洞试验的主要成果可作为类似工程结构设计的参考资料。     

Specification of the design wind load based on wind tunnel experiments

Once a high-quality wind tunnel experiment with no major flaws on the experimental side has been performed and the data have been processed/translated appropriately to the design-decisive variable, the final step is to estimate the appropriate load or load effect coefficient for the specification of the design wind load. Four questions arise: what is the appropriate length of a single run in the wind tunnel, what is the appropriate fractile of the observed extreme coefficients, how many independent experiments are required to estimate this fractile and what should be the target confidence interval. The paper tries to give some answers to these questions and discusses the findings in regard to some wind load codes.     

Wind tunnel evaluation of mean wind pressure on a frame-type signboard

In the context of the growing concern for the wind effects and the wind design of “street architecture” (bill-boards, traffic signs, traffic lights, etc.), wind tunnel tests have been carried out on a model of a frame-type signboard, placed within a regular array of buildings. The first experimental results, reported here, help to clarify the relationship between the wind loading on the signboard and the characteristics of the wind acting on the surrounding buildings.     

地铁活塞风特性的测试研究

测试了上海地铁车站内活塞风的情况,分析了所得的数据,结果表明,活塞风对车站内的气流组织产生了巨大影响,列车进站时,活塞风绝大部分进入站台,活塞风竖井基本不起作用;列车出站时,从室外吸入的空气会使站厅层内门厅处的温度瞬间升高(夏季)或降低(冬季)4～6℃;过渡季节可以利用活塞风竖井引入室外新风,减少能耗。     

Measurements of the cross wind forces on trains

The results of full-scale and wind tunnel experiments to measure the cross wind time averaged and unsteady forces and moments on trains are presented. The results demonstrate good agreement between the two sets of experiments but also illustrate the need for care in simulating local roughness effects in the wind tunnel simulation. It is also shown that quasi-steady effects need to be taken into account when calculating force and moment aerodynamic admittances.     

Indicators for the evaluation of wind tunnel test section flow quality and application to a numerical closed-circuit wind tunnel

The flow in a wind tunnel test section must meet high standards to obtain accurate and reliable measurement data. Good flow quality demands a certain degree of spatial uniformity and temporal steadiness of velocity and pressure. In this paper, a set of six new indices is developed and presented that relate spatial aspects of the mean velocity field to flow quality. One index quantifies the degree of uniformity of the velocity field and can be used directly as a flow quality indicator. The five other indices are related to different types of deviations from spatially uniform flow; skewed flow and angularity (up-flow and down-flow, swirl, cross-flow, diverging and converging flow). The indices can be used to evaluate the flow quality in existing tunnels, to assess the impact of design modifications, as well as to carry out CFD-based design of new wind tunnels. As an example, the indices are applied to assess the impact of guide vanes and screens on the test section flow quality in a numerical closed-circuit wind tunnel.     

数值风洞在大跨屋盖结构风荷载确定中的应用

运用计算流体力学数值模拟技术对大跨屋盖结构表面风荷载进行了研究。对平屋面和曲面屋面表面风压分布进行了数值模拟。在此基础上,对大庆石油学院体育馆屋盖表面进行了风洞试验和数值模拟的对比研究,并对大射电望远镜FAST反射面的风压分布及其周围流场进行了数值模拟,为该工程的结构抗风设计提供了参考。     

洛阳市电缆隧道多竖井工作面施工的测量

通过洛阳市电缆隧道施工测量的实例，总结了联系三角形法竖井定向方法及应注意的事项，提出了在没有明确的测量标准的前提下根据实际情况，利用误差理论对定向误差进行估算的方法。     

从风环境试验看建筑群对自身风环境的影响——深圳福田商城建筑风洞风环境试验研究

本文作者从建筑风环境的试验目的和评价标准出发 ,以试验原始数据为基础 ,对自成一个建筑群的深圳福田商城的风洞风环境试验结果进行了分析。     

热力效应作用下小区风环境风洞试验研究

温度作为影响城市舒适度的主要因素之一,对流场的作用机理到目前为止尚不明确。为揭示温度场对流场的影响规律,基于大尺寸风洞,对不同热力条件下的平均风进行试验研究,得出不同理查逊数R_b作用下的人行高度风速、相关测点顺风向速度和雷诺剪切应力分布并进行详细分析。以长沙市某小区为研究背景,探究了不同热力效应下人行高度风场的分布规律,获取了热力条件下典型测点的相关性系数,并利用超越概率的方法定量评估了热力效应下的小区人行高度风环境。结果表明:在-0.38<R_b<0范围内,空风洞流场随着热力效应增大,在近地面风速增长相对较大,且随着高度的增加其增幅逐渐减缓; 实际中小区人行高度风环境受温度影响整体较小,主要影响集中在风速比0.6以下,最大均方根为0.635,风速比在0.6以上时温度对风速影响效果相对较小; 热力效应对人行高度风场的相关性与舒适度影响较小,其最大影响值分别为8%和3.87%。     

大跨度曲面屋盖风压分布特性的试验研究

通过某机场航站楼的刚性模型风洞试验研究,得到了上下屋盖表面的平均、脉动风压系数,对其风压分布特性进行了研究。结果表明:上表面屋盖主要呈现负压,在屋盖迎风面边缘出现较大气流分离;下表面屋盖迎风面出现正压,背风面主要为负压,风压系数变化梯度较大,风荷载特性更加复杂。     

被上游建筑遮挡的下游建筑表面风压CFD模拟的可靠性研究

研究城市通风或建筑风环境的主要目的是探索建筑之间和建筑内外的气流运动及污染物扩散规律,主要手段有风洞实验和计算流体动力学（CFD）模拟,后者相对前者的优点是易操作且成本低,但由于流体运动的高度不确定性,其结果的准确性存疑。在城市中,建筑之间的互相遮挡是主要特征之一,提取其中最基本单元,把两个建筑之间的遮挡问题分为上游建筑有孔（如穿堂风）与无孔两种情况,运用CFD中的雷诺平均模型（RANS）模拟下游建筑表面的风压,并与风洞实验进行严格对比,以讨论CFD方法在这一基本单元问题中的可靠性。网格敏感性分析显示,建筑表面最小网格为建筑高度的2%时,可获得可靠的结果。5种常用RANS模型的结果与风洞实验严格对比表明：RANS模型对模拟上游有孔遮挡的可靠性明显高于模拟无孔遮挡;RANS模型对于建筑上部的风压模拟结果普遍好于建筑下部;其中,SST k-ω模型准确性最高,在上游有孔时,平均误差11%,上游无孔遮挡时,则为16%。     

水平弧形公路隧道临界风速研究

采用FDS建立弧形隧道火灾模型,对模型进行模拟计算,结合Wu&Bakar的临界风速预测模型和计算观测数据,应用MATLAB拟合工具箱建立弧形隧道的临界风速模型。利用该模型预测重庆市某公路隧道在发生火灾情况下的临界风速,将预测结果与Wu&Bakar模型和FDS的预测结果进行对比,结果表明,该模型比Wu&Bakar模型更加接近数值模拟的结果。     

Numerical modeling of the flow conditions in a closed-circuit low-speed wind tunnel

A methodology for numerically simulating the flow conditions in closed-circuit wind tunnels is developed as a contribution to the general philosophy of incorporating Computational Fluid Dynamics (CFD) in wind tunnel design and testing and to CFD validation studies. The methodology is applied to the full-scale Jules Verne climatic wind tunnel in which experimental data have been obtained. Due to the specific features of this closed-circuit wind tunnel, the conventional CFD modeling approach, in which only the flow in the wind tunnel test section is modeled, is inadequate. To obtain accurate results the entire wind tunnel has to be modeled. In the numerical closed-circuit wind tunnel, the conventional flow inlet and outlet are replaced by a single “fan boundary condition”. Special attention is given to the theoretical background and the practical implementation of this type of boundary condition in the CFD model. The numerical model is validated for the case of an empty wind tunnel and for the case in which a block-type building is placed in the test section. It will be shown that this methodology can generally reproduce the wind tunnel measurements of mean velocities with an error equal to or less than 10% despite the occurrence of multiple flow separations upstream of the test section. This provides perspectives for the future use of this methodology as a tool for wind tunnel design and testing and for CFD validation purposes.     

Simulation of honeycomb-screen combinations for turbulence management in a subsonic wind tunnel

Honeycomb and screens, mainly used for turbulence reduction, are the key elements of a subsonic wind tunnel. In this paper, design aspects of these elements are addressed for an open-circuit wind tunnel, installed at Indian Institute of Technology Guwahati (IITG), India. The effectiveness of honeycomb and honeycomb-screen combinations, in reducing swirl and turbulence level in the test section, is studied by simulating the flowfield using commercial computational fluid dynamics (CFD) package ANSYS-CFX. RNG k−ε turbulence model, with scalable wall functions, is used for modeling turbulence. Results of these simulations for turbulence management, using honeycombs of different lengths, cell shapes and screens of different open area ratios, are found to be in good agreement with experimental and theoretical results available in open literature. These simulations have confirmed the methodology to be adopted for design of wind tunnel subsections. Thus validated design parameters have been used for fabricating the honeycomb and screens for the IITG wind tunnel.     

Compensation of high-frequency components of wind load by wind tunnel testing

To analyze the wind-induced response of structures, wind tunnel tests are often carried out to determine the wind loads on structures. However, due to the influence of similarity requirements in wind tunnel tests, the resulting data from the model test still needs to be translated by similarity rules for predicting the real loads on prototype structures. During this process, an inevitable result is that the high-frequency components of fluctuating wind loads get lost, which leads to some unexpected errors in the subsequent wind-induced response analysis. To solve this problem, a frequency compensation method is put forward. The purpose of this method is to reconstruct the high-frequency part of fluctuating wind loads based on experimental data and some basic principles of the aerodynamics of bluff bodies. The causes and effects of the frequency compensation problem are discussed first, then a practical method of frequency compensation is proposed by combining the fluctuating wind energy spectrum theory and the Proper Orthogonal Decomposition technique. Based on this method, the wind-induced response of a single-layer reticulated shell is analyzed to show the validity and necessity of this method.