基于正交小波逆变换的空间相关性风场数值模拟

基于多分辨率分析的思想,利用正交小波基小波系数与功率谱密度函数的关系,以Davenport谱作为目标谱,通过逆小波变换,模拟出互不相关的风速时程,并考虑空间相关性,将其转换为具有空间相关性的风场.通过算例分析了所模拟风场各点风速时程的功率谱密度函数和互相关函数,均与目标值符合较好,证明了该方法的可行性和有效性.所模拟的空间相关性风场,可为结构风振时程分析提供荷载输入.     

脉动风荷载模拟中几点问题的探讨

本文列举了 2种规格化功率谱密度函数的表达式 ,简要介绍了脉动风荷载模拟的过程及方法。通过对 2种谱函数的分析和比较 ,提出了风荷载模拟中应该注意的问题以及经常容易出错的地方。文中通过对南京电视塔进行 1 6维脉动风荷载的模拟 ,比较了 2种规格化谱的各自特点 ,分析了误差产生的原因 ,并对各自的计算机耗时进行了比较 ,得出了某一规格化谱表达式较优的结论。     

几种常用风谱模型的对比研究

正确模拟脉动风场的前提是获得适当的脉动风功率谱的表达式.本文列举了目前风工程中普遍采用的五种风谱模型,从能量分布和风速时程的特点对以上谱模型进行了对比.本文还对在风场模拟中起关键作用的气动导纳函数和相关函数进行了讨论,浅析了两者在风场模拟中对不同风谱的影响.     

基于CQC方法的大跨屋盖结构随机风振响应计算

本从线性结构随机振动响应计算的CQC方法出发，推导出适合于大跨屋盖结构随机风振响应统计量精细计算的算式，式中考虑了不同振型响应之间互相关的影响；同时指出，如需按CQC方法进行精细计算，就必须首先获得结构各点风荷载之间互功率谱密度函数的实部和虚部。     

悬索拉线塔(塔线耦合模型)脉动风分析

基于脉动风的动力特性,采用谐波合成法以Davenport风谱模拟了多条风荷载时程曲线。在时间域内对输电塔做了风振响应时程分析。通过大量的数值模拟和统计分析得到脉动风功率谱和相干函数曲线以及悬索塔四线三塔的耦合模型的风振系数。     

上海崇明越江通道工程场地脉动风特性分析

采用现场实测的方法对上海市崇明岛侯家镇气象站的近地中强度脉动风特性进行分析研究,对紊流强度、阵风因子、紊流积分尺度的统计值与规范结果进行了比较,对水平方向和垂直方向常用的几种功率谱密度函数进行了拟合修正,提出了精度优于常用风谱的谱函数表达式.     

基于风压功率谱函数法输入的高层建筑结构动力特性

基于脉动风的基本理论和Davenport风荷载功率谱,介绍计算高层建筑结构顺风向动力响应的计算方法,提出在频域内对高层建筑结构迎风面通过施加风压功率谱的方法进行高层建筑结构的随机振动分析。借助ANSYS对结构进行定制功率谱函数并加载,得到高层建筑结构自振频率及风压谱施加后的模态、应力变化情况,并将函数加载结果与静力求解结果进行分析比较。     

POD在大跨屋盖风致响应计算中的应用

根据风洞试验同步多点压力扫描技术和本征正交分解方法重构作用于圆拱顶屋盖的脉动风力。对重构的脉动风荷载的时间历程曲线及其统计性质与实测风荷载进行比较。计算部分测压点上重构的风荷载的自功率谱、互功率谱及相干函数,并用实测荷载的功率谱作了检查。提出一种采用缩阶技术用完全二次型组合法计算大跨屋盖的风致响应的方法,这种方法利用少量本征模态计算缩阶的主坐标功率谱而得到脉动风荷载功率谱。为检验方法的效率,给出采用不同数目主坐标的圆拱顶屋盖部分节点竖向均方根位移的计算时间和计算误差,以及采用不同数目主坐标的缩阶技术得到的全部节点的竖向均方根位移响应的误差分布。     

顺风向脉动风速功率谱密度函数的分析研究

1、前言脉动风是风的动力成份,它是一种随机荷载,引起结构的随机振动。脉动风的数学模型包括概率分布特性、功率谱密度函数和空间相关性。脉动风速功率谱密度函数反映了紊流能量在频率域的分布状况,是进行结构随机振     

矩形高层建筑结构扭转风振反应时程的分析计算

根据Davenport脉动风速谱函数与日本规范中提出的横风向脉动风力谱系数函数模拟的顺风向与横风向脉动风压时程,采用Newmark法计算了一栋高68m的高层建筑物的风振扭转动力反应时程。计算时考虑了顺风向脉动风压与横风向脉动风压的联合作用。计算结果表明:结构扭转振动加速度响应以共振响应为主,非共振响应仅占次要的部分,这与谱分析法得出的结论是一致的,从而说明了计算结果的正确性。这对于正确估算结构的扭转风振反应值,为高层建筑风振控制措施设计提供参考依据是有一定意义的。     

传统井巷建筑原真风环境的数值模拟研究——以湘南宝镜村古民居为例

湘南天井排屋式传统民居的形态尺度与建筑群通风效能之间的关系存在紧密的气候适应性联系。通过现场调研与测绘获取气象数据，并应用Envi-met 软件对传统村落整体风环境进行模拟分析；然后，以该模拟结果作为边界条件，对典型天井排屋的室内风环境进行逐一模拟与评价；最后，以前两步结果作为原型边界条件，模拟对比不同尺度组合下的井巷风环境总结并变化规律。研究结果表明，随着宝镜村古民居进深增加，夏季风速先增后减，冬季风速先增大后平稳；风速与井巷高度正相关，与宽度没有明显关联；建筑群进深34.3m、宽度3m、高度6.6m 的尺度组合通风效果最佳。建议将井巷高度相对较高，进深相对适中的尺度作为符合宝镜村当地气候适应性的地域性井巷建筑量化设计参考。     

超高层建筑表面风荷载数值模拟研究

该文通过计算流体力学数值模拟技术对某超高层建筑进行了表面风荷载分布的数值模拟。结果表明：由于漩涡脱落,在结构侧面边缘出现了较强烈的负压区;在周边建筑干扰高度范围内,结构表面风压分布较混乱,结构在干扰高度以上部分风压分布比较规律;局部部位的设计风压应参考各风向角下风压峰值。     

建筑形态参数对街道型风道通风潜力影响分析

建筑形态参数直接影响城市街道型 风道的通风潜力。为揭示中国大城市建筑形态参 数对街道型风道通风效果的影响程度与机理, 首先选择南京市中心区中山路两侧约10.84 km 2 的街区为研究样区,基于python软件从高分辨 率遥感图像中提取研究样区内建筑密度、建筑 高度和容积率;其次,借助CFD平台,通过验证 参数后的量化模拟获得该街区在1.5 m、10 m 与30 m等高度的风场图,以揭示模拟风场与 建筑形态参数之间的相关性以及建筑形态参 数对城市通风潜力的影响。结果表明：在各高 度,风速与建筑密度曲线走势相反,风速较高 处与路口的位置基本一致;建筑密度与模拟风 速呈负相关关系,相关系数为0.040（1.5 m）、 -0.475（10 m）与-0.314（30 m）,建筑高度与模 拟风速呈正相关关系,相关系数为0.237,容积 率与模拟风速无明显相关性。最后,结合南京 城市核心区的建成环境特点,提出改善我国大 城市街道型风道通风潜力的建筑形态参数规划 应对策略。     

Wind tunnel tests on scale models of a large power station chimney

This work is aimed at providing a better understanding of the parameters required for the wind-tunnel simulation of the wind loads on large power station chimneys. Measurements of mean and fluctuating pressure distributions have been made on scale models of Fawley power station chimney, for comparison with the full-scale measurements of Tunstall. The measurements have been made in a simulated atmospheric boundary layer of height 1.2 m (nominal scale 1:500), using the method developed by Counihan.Initial measurements of mean pressure distribution were made on a 1:250 scale model chimney in the 1:500 scale boundary layer, in order to obtain as high a Reynolds number as possible in the wind tunnel available. No fluctuating pressure measurements were made owing to the limited tunnel time available. Following the good agreement between mean pressure distributions obtained on the 1:250 model and full-scale measurements, a 1:500 scale model chimney was tested in the same simulated atmospheric boundary layer. Mean pressure measurements gave good agreement with full-scale measurements at a Reynolds number of 2.3 × 10⁷, for model Reynolds numbers above 1.5 × 10⁵, and with a smooth or slightly rough model surface. Good agreement was obtained between model and full scale for the distribution of fluctuating pressure coefficients, when the difference in turbulence intensity between the simulated and full-scale flow was considered. No coherent vortex shedding was found on the model, in agreement with full-scale measurements.     

基于台风风谱的电视塔风场数值模拟

针对上海青浦电视塔的结构形式及振动型态的特点,考虑脉动风的竖向相关性以及电视塔结构风速谱随竖向位置变化的特性,本文基于台风基本特性,采用随高度变化的田浦台风风速谱以及不随高度变化的石沅台风风速谱,运用数值模拟方法,仿真得到了与塔高竖向相关的43条脉动风速时程样本。经与采用不随高度变化的Davenport谱的结果相比较,得出一些有意义的结论。为提高计算效率和计算精度,引入了快速傅立叶变换技术。通过比较自功率谱和自相关函数可以看出,模拟值和目标值吻合得很好,从而验证了本文计算的准确性与有效性。     

Measurements of wind drag on people standing in a wind tunnel

This report describes an experiment in which measurements were made of the wind drag on 331 people standing in turn in a wind tunnel. The results were analysed in terms of projected areas and drag coefficients, as is customary with wind tunnel measurements. Areas were then expressed as ratios to a person's total body surface area, calculated from weight and height. It was found that these area ratios and the drag coefficients could be related to the type of clothing, and eight categories were selected. The results thus provide a simple way of estimating the wind drag on a person for a known windspeed if his weight, height and type of cloting are known.     

Large-eddy simulation of atmospheric boundary layer flow through wind turbines and wind farms

Accurate prediction of atmospheric boundary layer (ABL) flow and its interactions with wind turbines and wind farms is critical for optimizing the design (turbine siting) of wind energy projects. Large-eddy simulation (LES) can potentially provide the kind of high-resolution spatial and temporal information needed to maximize wind energy production and minimize fatigue loads in wind farms. However, the accuracy of LESs of ABL flow with wind turbines hinges on our ability to parameterize subgrid-scale (SGS) turbulent fluxes as well as turbine-induced forces. This paper focuses on recent research efforts to develop and validate an LES framework for wind energy applications. SGS fluxes are parameterized using tuning-free Lagrangian scale-dependent dynamic models. These models optimize the local value of the model coefficients based on the dynamics of the resolved scales. The turbine-induced forces (e.g., thrust, lift and drag) are parameterized using two types of models: actuator-disk models that distribute the force loading over the rotor disk, and actuator-line models that distribute the forces along lines that follow the position of the blades. Simulation results are compared to wind-tunnel measurements collected with hot-wire anemometry in the wake of a miniature three-blade wind turbine placed in a boundary layer flow. In general, the characteristics of the turbine wakes simulated with the proposed LES framework are in good agreement with the measurements in the far-wake region. Near the turbine, up to about five rotor diameters downwind, the best performance is obtained with turbine models that induce wake-flow rotation and account for the non-uniformity of the turbine-induced forces. Finally, the LES framework is used to simulate atmospheric boundary-layer flow through an operational wind farm.     

Wind effects on the world’s longest spatial lattice structure: Loading characteristics and numerical prediction

The 486-m long roof structure of Shenzhen Citizens’ Centre is the world’s longest spatial lattice structure. This paper presents some selected results from a combined wind tunnel and numerical simulation study of wind effects on the extra-long-span roof structure. In this study, simultaneous pressure measurements on its entire roof are made in a boundary layer wind tunnel, and the measured wind pressures, such as mean, root-mean-square (rms) and peak pressure coefficient distributions on the roof are presented and discussed. Based on the measured data from a number of pressure taps, a numerical simulation approach using backpropagation neural networks (BPNN) is developed for the predictions of wind-induced pressure time series at other roof locations which are not covered in the wind tunnel measurements. The BPNN is trained with the pressure data time series measured from adjacent pressure taps. The good performance of the developed neural network is demonstrated by comparing the predictions with the model test results, illustrating that the BPNN approach can serve as an effective tool for the design and analysis of wind effects on large roof structures in conjunction with wind tunnel tests.     

数值模拟大气边界层风洞中湍流模型的比较

风洞模拟试验是风工程研究的一种重要手段,在对大气边界层风洞进行数值模拟的时候,湍流模型的选取是影响模拟计算结果的至关重要的因素之一,本文针对大气边界层的风洞模型为考察对象对湍流模型进行了考察,考虑了各种湍流模型对计算结果的影响,并与实验结果进行了对比,旨在得出大气边界层风洞模拟中比较适合的湍流模型。研究发现在模拟大气边界层的风洞时,一般宜采用RNG k-ε模型,在计算资源和时间允许的情况下,建议使用雷诺应力模型。     

大跨度斜拉桥三维脉动风场模拟

针对大跨度斜拉桥结构形式及振动型态的特点,结合自然风的相关特性,提出了一种简化的三维脉动风速场模拟方法,将实际面状的三维脉动风速场简化为多个线状的一维脉动风速场。基于谱解法,采用互谱密度矩阵Cholesky分解的显式表达,并运用FFT技术,以京沪高速南京长江大桥为工程实例,进行了三维脉动风场的模拟,并对模拟样本进行检验,结果表明模拟值与目标值吻合良好。