深圳平安国际金融大厦风致响应大涡模拟分析

运用一种新的湍流脉动流场产生方法模拟了三种风场的湍流边界条件,采用一种新的大涡模拟的亚格子模型,基于Linux系统下软件平台Fluent 6.3的并行计算技术,对深圳平安国际金融大厦进行了全尺寸、高雷诺数（高达10×10⁸量级）的数值风洞模拟。计算了三种风场下建筑表面平均、脉动风压及风荷载时程数据。利用惯性风荷载（IWL）法得到三种风场下深圳平安金融大厦的基底等效静风荷载以及结构顶部峰值加速度响应。分析了不同的湍流来流对结构风压系数、风荷载及加速度响应的影响。分析结果表明：三种来流风场条件下,深圳平安金融大厦周围风场相差较大,来流的湍流强度越高,建筑物前方的脉动风速越高;顺风向等效风荷载主要受平均风速控制,横风向等效风荷载主要受脉动风控制;湍流强度越大,横风向等效风荷载越大;中国规范建议的湍流流场下,深圳平安金融大厦10年重现期顺风向、横风向峰值加速度响应满足居住者舒适度要求。     

大跨度屋盖结构台风效应的风洞试验与实测

为研究台风风场高湍流特性对大跨度屋盖结构风压分布的影响,依据台风"海葵"的实测风速时程,确定了风洞试验中模拟台风风场的风剖面,进行了台风风场下某体育馆屋盖的测压风洞试验。考察了台风风场下大跨度屋盖结构的风压分布特性,并与常规B类风场下的风压数据以及实测风压数据进行对比,研究了台风效应对大跨度屋盖结构风压分布的影响。研究表明,台风风场和常规B类风场下的平均风压系数以及脉动风压系数的分布规律基本相似,但台风风场下的风压数值较常规B类风场大,而且更接近于实测风压值。     

大跨度双曲混凝土双曲组合扭壳屋盖表面风压系数试验研究

大跨度双曲混凝土组合扭壳屋盖结构具有质量轻、柔性大、阻尼小等特点,风荷载是其结构设计的控制荷载.由于建筑造型的要求,大跨度双曲混凝土屋盖结构往往具有复杂的外型,现行的荷载规范很难确定屋盖表面的风压分布,一般是通过风洞测压试验获得屋盖表面的风压.本文较为详细地介绍了具体试验方法和理论分析方法,并通过对大跨度双曲混凝土组合扭壳屋盖表面风压系数的测定和风洞试验结果的分析,说明了利用风洞试验测量其表面风荷载的必要性,得到其风压分布的复杂特征,为大跨度混凝土屋盖的结构设计提供参考.     

双拱大跨屋盖结构风载的数值模拟研究

双拱大跨度网架屋盖结构由于体表为复杂曲面,其风荷载的确定不能仅参考我国建筑结构荷载规范中对风荷载的相关规定,风荷载的确定需要借助于其他手段。CFD数值模拟风洞是近年来发展起来的一种风荷载研究手段,基于ANSYS-CFX 12流体动力学软件,利用雷诺应力（RSM）湍流模型对一双拱大跨度屋盖结构上平均风载体型系数进行数值模...     

厦门市文化艺术中心综合楼屋顶膜结构风压数值模拟

大跨屋盖结构形体多为复杂曲面,荷载规范的规定往往不能满足设计需求,风荷载的确定需借助于其他手段,而CFD数值模拟是近年来兴起的一种风荷载研究手段．本文基于FLUENT平台,对厦门文化艺术中心共享综合楼屋顶膜结构进行了数值风洞试验研究,湍流模型采用雷诺应力（RSM）模型．数值模拟结果表明,膜结构表面风压分布与其表面形状密切相关,在曲率变化大的局部区域风压变化也很剧烈,在设计时需引起相当重视．同时结合屋盖周围的流场特点,对屋盖表面平均风压的分布规律进行了分析,并根据不同风向下风压分布特性对膜结构表面进行了分区,并给出可供工程设计参考的分区风载体型系数．基于以上工作,说明CFD数值模拟为复杂工程提供辅助设计信息是可行的．     

大跨度结构风荷载的风洞试验和CFD数值模拟研究

针对某大跨度结构,进行动态测压风洞试验和风荷载数值模拟研究。通过风洞试验,给出了该大跨度体育馆屋面及四周立面表面的风压系数,并分析了风压分布的特征,为该工程的主体和围护结构抗风设计提供详细的风荷载数据。通过数值模拟研究,探讨复杂体型建筑表面平均风压CFD数值模拟的可行性,提出了应用于复杂工程CFD数值模拟时的网格划分方法,有效地减少了多个风向角时的建模工作量。计算结果表明,体育馆表面的风压与风洞试验结果基本一致;在局部区域存在较大误差。最后比较了网格密度、湍流模型对数值计算精度的影响。CFD数值模拟简洁、高效,能获得丰富的数据成果,可以用于复杂工程的平均风荷载研究。     

斜风向下低矮房屋屋盖风荷载特性试验研究

基于一个低矮房屋刚性模型风洞试验,研究了湍流场中低矮房屋屋盖角部未开孔和开孔时屋盖上的风荷载分布特性。研究结果表明:在斜风向作用下,屋盖迎风角部风荷载表现出复杂的三维特性,屋盖迎风角部也是较大风吸力作用的区域;湍流场中锥形涡之间在屋盖区域没有相互作用;采用二次曲线对涡核位置和再附位置进行拟合,拟合结果较好;屋盖内表面风荷载平均效应趋于均匀,脉动风压效应在时域和频域上表现出很高的相关性,并表现出明显的Helmholtz共振现象。     

平滑流场内半圆球形大跨屋盖非定常绕流大涡模拟

基于Fluent软件平台,进行了平滑流场内不同雷诺数情况下半圆球形屋盖结构非定常绕流大涡模拟计算。数值模拟中,以来流平均风速和半圆球屋盖直径定义的3个雷诺数Re为6.6×10~4、3.0×10~5和2.0×10~6。将数值模拟所得屋盖表面平均和脉动风压与已有文献风洞试验结果进行对比,验证了文中数值模拟结果的有效性,并分析了不同大涡模拟参数对数值模拟结果的影响。比较分析了3个雷诺数下半圆球形屋盖结构周围的平均流场和瞬态涡结构分布规律,研究半圆球屋盖结构风荷载的形成机理。结果表明:在保证第1层网格到壁面的无量纲距离y~+≤5.0情况下,进一步加密网格对屋盖表面风压分布影响不明显,而亚格子模型对屋盖表面风压分布影响显著。随着雷诺数的增加,屋盖表面流动分离点逐渐下移,地面上的流动再附点则逐渐前移,上游回流区和下游分离泡均逐渐变小;屋盖表面流动分离区剪切涡形状随雷诺数的增大逐渐变得不规则。     

锥状涡作用下大跨度平屋盖表面脉动风压谱模型研究

锥状涡是大跨度平屋盖表面在斜风向来流作用下形成的一种特征湍流形式,相对于来流垂直于檐口时所形成的柱状涡而言,锥状涡的作用形态更为复杂,破坏性更强。基于风洞测压试验,对锥状涡作用下平屋盖表面不同位置处的脉动风压谱特性进行研究,探讨脉动风压谱形状与分离、再附、漩涡脱落等流动现象之间的联系,归纳出四类典型的脉动风压谱形式;在此基础上,提出由来流湍流影响项和特征湍流影响项组成的脉动风压谱多项式模型,并通过引入权重系数来反映不同湍流影响项的贡献。研究结果表明,通过权重系数的分布可以划分流场影响区域,具有一定的物理意义。同时考察脉动风压的空间相关性,研究表明,在锥形涡作用使得屋盖表面脉动风压相关性强于来流脉动风速,相干函数用指数衰减函数表示,衰减系数可取2.5。最后,通过风振响应分析结果来比较风压谱模型对风振响应结果的影响,结果表明,拟定常假设低估了结构的脉动响应,而基于文中的简化风压谱模型得到的风振响应结果与风洞试验结果吻合较好。研究为进一步建立统一的屋盖脉动风压谱模型奠定了基础。     

三维脉动风模拟技术在大跨机库风振分析中的应用

风荷载在大跨度屋盖结构设计中往往起主要作用,这使得该类结构的风荷载及风致动力响应研究日益受到关注与重视。结合大跨度机库屋盖表面脉动风作用特点,依据改进的Iwatani线性回归滤波器法并结合中心采样定理,实现了基于Matlab的超大跨度网架结构三维空间相关脉动风速时程模拟。以Davenport谱为目标谱对首都机场六机位机库网架所有上弦节点位置处的随机脉动风速时程进行了模拟。进而结合风洞试验数据,依据屋盖各节点风压系数将模拟的风速时程加载于机库结构并进行风振响应时域分析,以研究三维脉动风作用下超大跨度机库屋盖结构的响应特点。分析结果表明本文模拟空间随机脉动风的方法可以较好地考虑大跨机库表面的脉动风特点,为结构的风振时域分析提供准确的荷载时程。     

Large eddy simulation of wind effects on a long-span complex roof structure

This paper presents a combined study of numerical simulations and wind tunnel tests for the determinations of wind effects on a long-span complex roof of the Shenzhen New Railway Station Building. The main objective of this study is to present an effective approach for the estimations of wind effects on a complex roof by computational fluid dynamics (CFD) techniques. A new inflow turbulence generator called the discretizing and synthesizing random flow generation (DSRFG) approach was applied to simulate inflow boundary conditions of a turbulent flow field. A new one-equation dynamic subgrid scale (SGS) model was adopted for the large eddy simulations (LES) of wind effects on the station building. The wind-induced pressures on the roof and turbulent flow fields around the station building were thus calculated based upon the DSRFG approach and the new SGS model integrated with the FLUENT software. In parallel with the numerical investigation, simultaneous pressure measurements on the entire station building were made in a boundary layer wind tunnel to determine the mean, fluctuating, and peak pressure coefficient distributions. The numerically predicted results were found to be consistent with the wind tunnel test data. The comparative study demonstrated that the recommended inflow turbulence generation technique and the new SGS model as well as the associated numerical treatments are useful tools for structural engineers to assess wind effects on long-span complex roofs and irregularly shaped buildings at the design stage.     

高层建筑标准模型脉动风压特性大涡模拟适用方法研究

为提高钝体建筑结构绕流模拟结果的精度,基于两种大涡模拟(large eddy simulation, LES)入口湍流生成方法,分别为NSRFG（narrow band synthesis random flow generation）方法和CDRFG（consistent discretizing random flow generation）方法,进行CAARC(commonwealth advisory aeronautical research concil)高层建筑标准模型绕流的数值模拟比较研究。以风洞试验结果为参照,在对大气边界层湍流风场进行模拟验证的基础上,详细对比分析采用上述两种方法模拟得到的建筑表面平均和脉动风压系数、绕流场湍流结构、风压系数概率密度分布特性等的差异,并着重从脉动风压非高斯特性角度进行探讨,检验采用上述两种方法模拟钝体建筑结构绕流的适用性和准确性。结果显示：在受来流直接作用的建筑迎风面,采用两种方法模拟的脉动风压基本都符合高斯特性;而在受分离流和尾流作用的侧风面和背风面,采用NSRFG方法能更好地反映建筑表面脉动风压的非高斯特性。极值风压分析表明,为了满足99.38%的保证率,CAARC标准模型迎风面极大与极小峰值因子需分别取为3.0和2.5,侧风面和背风面极大和极小峰值因子需分别取为2.5和4.0。     

Study on suitable method to simulate fluctuating wind pressurecharacteristics of standard high-rise building model based on LES

为提高钝体建筑结构绕流模拟结果的精度，基于两种大涡模拟(large eddy simulation, LES)入口湍流生成方法，分别为NSRFG（narrow band synthesis random flow generation）方法和CDRFG（consistent discretizing random flow generation）方法，进行CAARC(commonwealth advisory aeronautical research concil)高层建筑标准模型绕流的数值模拟比较研究。以风洞试验结果为参照，在对大气边界层湍流风场进行模拟验证的基础上，详细对比分析采用上述两种方法模拟得到的建筑表面平均和脉动风压系数、绕流场湍流结构、风压系数概率密度分布特性等的差异，并着重从脉动风压非高斯特性角度进行探讨，检验采用上述两种方法模拟钝体建筑结构绕流的适用性和准确性。结果显示：在受来流直接作用的建筑迎风面，采用两种方法模拟的脉动风压基本都符合高斯特性；而在受分离流和尾流作用的侧风面和背风面，采用NSRFG方法能更好地反映建筑表面脉动风压的非高斯特性。极值风压分析表明，为了满足99.38%的保证率，CAARC标准模型迎风面极大与极小峰值因子需分别取为3.0和2.5，侧风面和背风面极大和极小峰值因子需分别取为2.5和4.0。     

湍流边界层中低矮建筑绕流大涡模拟

通过对平板湍流边界层进行大涡模拟,采用拟周期边界条件维持湍流边界层厚度稳定,提取速度和压力时程作为低矮建筑绕流模拟之脉动入流边界条件,研究脉动入流下的低矮建筑绕流特性。研究结果表明：入流边界特性对网格变化适应性良好,其平均速度剖面、湍流强度、流速频谱特性基本符合空旷地貌风场特性;脉动入流下,建筑表面的平均风压系数、脉动风压系数的计算结果与风洞试验结果基本吻合。受雷诺数及湍流强度的影响,流动分离区负压与试验值存在一定差别;屋盖上分离区风压时程具有非高斯概率特性,尤以气流分离较剧烈的屋盖迎风边缘及屋盖两侧风压的非高斯特性明显,该特征与风洞试验基本一致;受非高斯特性的影响,建议峰值因子g取4.5~5.5。     

Unsteady RANS simulations of flow around a bridge section

This paper presents the results of unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of flow around a common bridge deck geometry. Computations are performed with a noncommercial unstructured flow solver using two-dimensional hybrid meshes with fine near-wall resolution. The influence of different simulation parameters (grid refinement, time-step size, turbulence modelling) is analyzed, in particular in order to obtain flow solutions independent of spatial and temporal discretization. Results given by a one-equation eddy-viscosity turbulence model and a two-equation explicit algebraic Reynolds stress model are compared. Despite the limits imposed by the URANS approach and the relatively inexpensive two-dimensional computations, satisfactory agreement is found with the experimentally measured forces and pressures. These simulations help to explain the discrepancy between the results of two wind-tunnel test campaigns and show the dramatic influence of non-perfectly sharp edges on the global flow field development. The capability of the numerical approach to capture complex Reynolds number effects is also discussed.     

On the propagation of uncertainty in inflow turbulence to wind turbine loads

When stochastic simulation of inflow turbulence random fields is employed in the analysis or design of wind turbines in normal operating states, it is common to use well-established standard spectral models represented in terms of parameters that are usually treated as fixed or deterministic values. Studies have suggested, though, that many of these spectral parameters can exhibit some degree of variability. It is not unreasonable to expect, then, that derived flow fields based on simulation with such spectral models can be in turn highly variable for different realizations. Turbine load and performance variability would also be expected to result if response simulations are carried out with these variable flow fields. The aim here is to assess the extent of variability in derived inflow turbulence fields that arises from the noted variability in spectral model parameters. Simulation of these parameters as random variables forms the basis of this study. A commercial-sized 1.5 MW concept wind turbine is considered in the numerical studies. Variability in turbulence power spectra at field points on the rotor plane and in turbulence coherence functions for separations on the order of a rotor diameter and smaller is studied. Using time domain simulations, variability in various wind turbine response measures is also studied where the focus is on statistics such as response root-mean-square and 10-min extreme estimates. It is seen that while variability in inflow turbulence spectra can be great, the variability in turbine loads is generally considerably lower. One exception is for turbine yaw loads whose larger variability arises due to sensitivity to a coherence decay parameter that is itself highly variable. Finally, because reduced-order representations of turbulence random fields using empirical orthogonal decomposition techniques allow useful physical insights into spatial patterns of flow, variability in the energy distribution and the shapes of such empirical eigenmodes is studied and a simplified model is proposed that retains key variability sources in a limited number of modes and that accurately preserves overall inflow turbulence field uncertainty.     

世博轴膜面平均风压的数值模拟研究

基于Fluent 6软件平台,利用Realizablek-ε湍流模型对世博轴大跨膜结构屋面的平均风荷载进行了数值模拟研究。首先,通过与刚性模型测压风洞试验结果的对比,验证了数值模拟计算的有效性。然后,着重研究了周边建筑对膜表面平均风压分布的影响。最后,从数值模拟得到的流场信息分析了周边建筑对膜表面平均风压分布影响的机理。结果表明:周边建筑对膜表面局部风压分布有一定的影响,主要是由于上游建筑的"遮挡"改变了膜表面附近气流的流动状态,使建筑后面区域膜表面局部风压的绝对值有所减小,但随着上游建筑与膜结构之间距离的增大,这种影响逐渐减弱,并且远离上游建筑位置的膜表面风压基本不受影响。     

Flow around a cube in a turbulent boundary layer: LES and experiment

We present a numerical simulation of flow around a surface mounted cube placed in a turbulent boundary layer which, although representing a typical wind environment, has been specifically tailored to match a series of wind tunnel observations. The simulations were carried out at a Reynolds number, based on the velocity U at the cube height h, of 20,000—large enough that many aspects of the flow are effectively Reynolds number independent. The turbulence intensity was about 18% at the cube height, and the integral length scale was about 0.8 times the cube height h. The Jenson number Je=h/z₀, based on the approach flow roughness length z₀, was 600, to match the wind tunnel situation. The computational mesh was uniform with a spacing of h/32, aiding rapid convergence of the multigrid solver, and the governing equations were discretised using second-order finite differences within a parallel multiblock environment. The results presented include detailed comparison between measurements and LES computations of both the inflow boundary layer and the flow field around the cube including mean and fluctuating surface pressures. It is concluded that provided properly formulated inflow and surface boundary conditions are used, LES is now a viable tool for use in wind engineering problems concerning flow over isolated bodies. In particular, both mean and fluctuating surface pressures can be obtained with a similar degree of uncertainty as usually associated with wind tunnel modelling.     

“天使之翼”体育场风压特性试验

通过对梅州体育场进行测压试验,得到平均风压系数、脉动风压系数,对其风压特性做了详细分析。结果表明:控制体育场屋面的风压主要为负压,屋盖凸起处气流分离较大,导致其负压较大;当来流由低屋面进入高屋面时,在高屋面区域产生“上吸下顶”的受荷情况,负压增大;通过对屋盖测点风压时程第三、第四阶矩的统计分析发现,非高斯性测点主要分布在屋盖气流分离区和受尾流旋涡影响的区域;高斯分布和三参数伽马分布能较好地描述体育场表面风压概率特性;Sadek-Simiu法考虑了脉动风压非高斯特性,能准确地估计非高斯风压的极值。