Multivariate stationary non-Gaussian process simulation for wind pressure fields

Stochastic simulation is an important means of acquiring fluctuating wind pressures for wind induced response analyses in structural engineering. The wind pressure acting on a large-span space structure can be characterized as a stationary non-Gaussian field. This paper reviews several simulation algorithms related to the Spectral Representation Method （SRM） and the Static Transformation Method （STM）. Polynomial and Exponential transformation functions （PSTM and ESTM） are discussed. Deficiencies in current algorithms, with respect to accuracy, stability and efficiency, are analyzed, and the algorithms are improved for better practical application. In order to verify the improved algorithm, wind pressure fields on a large-span roof are simulated and compared with wind tunnel data. The simulation results fit well with the wind tunnel data, and the algorithm accuracy, stability and efficiency are shown to be better than those of current algorithms.

Paradigm of Numerical Simulation of SpatialWind Field for Disaster Prevention of Transmission Tower Lines

Numerical simulation of the spatial wind field plays a very important role in the study of wind-induced response law of transmission tower structures.A reasonable construction of a numerical simulation method of the wind field is conducive to the study of wind-induced response law under the action of an actual wind field.Currently,many research studies rely on simulating spatial wind fields as Gaussian wind,often overlooking the basic non-Gaussian characteristics.This paper aims to provide a comprehensive overview of the historical development and current state of spatial wind field simulations,along with a detailed introduction to standard simulation methods.Furthermore,it delves into the composition and unique characteristics of spatial winds.The process of fluctuating wind simulation based on the linear filter AR method is improved by introducing spatial correlation and non-Gaussian distribution characteristics.The numerical simulation method of the wind field is verified by taking the actual transmission tower as a calculation case.The results show that the method summarized in this paper has a broader application range and can effectively simulate the actual spatial wind field under various conditions,which provides a valuable data basis for the subsequent research on the wind-induced response of transmission tower lines.

Non-Gaussian Lagrangian Stochastic Model for Wind Field Simulation in the Surface Layer

Wind field simulation in the surface layer is often used to manage natural resources in terms of air quality,gene flow(through pollen drift),and plant disease transmission(spore dispersion).Although Lagrangian stochastic(LS)models describe stochastic wind behaviors,such models assume that wind velocities follow Gaussian distributions.However,measured surface-layer wind velocities show a strong skewness and kurtosis.This paper presents an improved model,a non-Gaussian LS model,which incorporates controllable non-Gaussian random variables to simulate the targeted non-Gaussian velocity distribution with more accurate skewness and kurtosis.Wind velocity statistics generated by the non-Gaussian model are evaluated by using the field data from the Cooperative Atmospheric Surface Exchange Study,October 1999 experimental dataset and comparing the data with statistics from the original Gaussian model.Results show that the non-Gaussian model improves the wind trajectory simulation by stably producing precise skewness and kurtosis in simulated wind velocities without sacrificing other features of the traditional Gaussian LS model,such as the accuracy in the mean and variance of simulated velocities.This improvement also leads to better accuracy in friction velocity(i.e.,a coupling of three-dimensional velocities).The model can also accommodate various non-Gaussian wind fields and a wide range of skewness–kurtosis combinations.Moreover,improved skewness and kurtosis in the simulated velocity will result in a significantly different dispersion for wind/particle simulations.Thus,the non-Gaussian model is worth applying to wind field simulation in the surface layer.

Numerical simulation of non-gaussian process of wind waves

In this paper further mathematical analysis on 'correlation transfer technique' by Polge el al. is carried out, the tenable conditions and the extent of suitability for the said method are proved as well. In consideration of the influence of skewness of the sea surface elevation on spectral shape, a 'quasi-correlation transfer techique' is developed by the modification of the simulated target spectrum. Meanwhile, the numerical simulation of the non-Gaussian process of wind waves is carried out in view of the two conditions of the surface elevation probability distribution and the spectrum. By using its simulated results, the influence of skewness of the sea surface elevation on two parameters in the distribution of wave heights (which had been fitted by using the Weibull distribution) is analysed. The 'quasi- correlation tranfer technique' is verified and compared with the selection wave data observed in the Jiaozhou Bay in the period of 1980 to 1981. Results make clear (hat, as far as the statistical distribution of the wave heights and the distribution of the maximum (minimum) values of the sea surface elevation are concerned, the said method is obviously superior to the conventional mothed of the linear wave superposition, and that the simulated results are closer to the observation data.

Wind tunnel simulation of wind loading on a solid structure of revolution

The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.

基于Flow Simulation的高风压离心式风机设计

离心式风机的风压与其径向尺寸有着紧密的联系,设计时如果要求结构尺寸紧凑又要达到比较大的风压时会很难兼顾。设计过程尝试了从改进叶轮结构形状和叶片的安装角度来解决这一问题。通过气动力计算得到了叶片安装的入口和出口角度及相关尺寸,最终采用了前向型叶轮结构。依据计算的几何参数借助Solidworks三维设计软件建立了风机的几何模型。最后利用软件的Flow Simulation模块对风机进行了风压和流速的数值模拟分析,分析结果显示选用的前向型叶片满足了设计要求。

Wind tunnel test for wind pressure characteristics on a saddle roof

The wind pressure characteristics on a saddle roof at wind direction along the connection of the low points are systematically studied by the wind tunnel test. First, the distributions of the mean and the fluctuating pressures on the saddle roof are provided. Through the wind pressure spectra, the process of generation, growth and break down of the vortex on the leading edge is presented from a microscopic aspect and then the distribution mechanism of the mean and fluctuating pressures along the vulnerable leading edge is explained. By analysis of the wind pressure spectra near the high points, it can be inferred that the body induced turbulence reflects itself as a high-frequency pressure fluctuation. Secondly, the third-and fourth-order statistical moments of the wind pressure are employed to identify the non-Gaussian nature of the pressure time history and to construct an easy tool to localize regions with a non-Gaussian feature. The cause of the non-Gaussian feature is discussed by virtue of the wind pressure spectra. It is concluded that the non-Gaussian feature of the wind pressure originates from the effects of flow separation and body-induced turbulence, and the former effect plays an obvious role.

Numerical simulation study of gob air leakage field and gas migration regularity in downlink ventilation

Aiming at the issue that mass of gas emission from mining gob and the gas exceeded in working face, gob air leakage field and gas migration regularity in downlink ventilation was studied. In consideration of the influence of natural wind pressure to analyze the stope face differential pressure, gob air leakage field distribution and gas migration regularity theoretically. Established a two-dimensional physical model with one source and one doab, and applied computational fluid dynamics analysis software Fluent to do numerical simulation, analyzed and contrasted to the areas of gob air leakage on size and gas emission from gob to working face on strength when using the downlink ventilation and uplink ventilation. When applied downward ventilation in stope face, the air leakage field of gob nearly working face, and the air leakage intensity were smaller than uplink, this can effectively reduce the gas emission from gob to working face; when used downlink ventilation, the air leakage airflow carry the lower amount of gas to doab than uplink ventilation, and more easily to mix the gas, reduced the possibility of gas accumulation in upper comer and the stratified flows, it can provide protection to mine with safe and effective production.

沈阳恒隆市府广场超高层塔楼风荷载分析研究

为了确定高度350.6m沈阳恒隆市府广场塔楼结构设计的风荷载,采用刚性风洞试验与风洞数值模拟相结合的方法分析塔楼的风荷载,风洞试验研究给出楼层剪力与扭矩及风致加速度。采用四种湍流模型进行风洞数值模拟,分析建筑平均风压系数、体型系数、基底剪力及倾覆力矩,并与风洞试验进行比较,得出适用于超高层建筑风洞模拟的湍流分析模型,利用该分析模型的数值风洞模拟技术,分析塔楼13个风向角的风压系数、体型系数和基底剪力,为结构风荷载取值提供依据。研究结果表明:相比于《建筑结构荷载规范》(GB 50009—2012)对近似矩形平面建筑物的体型系数的规定,RSM模型迎风面0.83、背风面-0.56,与规范矩形截面迎风面0.8、背风面-0.6最为接近;RSM模型与试验吻合最好;选取RSM模型来分析超高层等大型复杂结构风荷载,能够得到较为准确的结果。

基于时间自动机的动力调度岗位培训仿真机理建模

针对大型风洞群中压空气系统存在调度机理复杂、岗位人员素质要求高、系统实操培训代价大等问题,实施基于时间自动机的动力调度岗位培训仿真机理建模。通过混杂系统理论提出适合大型风洞群中压空气调度的扩展时间自动机模型,基于先来先服务策略构建资源申请、机组工作等队列,建立调度器、就地执行器等核心机理模型,并采用UPPAAL工具对模型进行验证。结果表明:该模型的建立不仅为岗位人员掌握设备结构原理、积累实操经验提供有效手段,而且为建立风洞试验调度仿真系统、合理有效实施风洞动力调度岗位培训打下了基础。

地下进风系统对间接空冷塔性能的影响

削弱环境风对间接空冷塔散热器性能的不利影响,有助于其安全和经济运行。该文提出一种新型间接空冷塔地下进风系统,将空冷散热器整体布置在低于地表平面的地下空间内。建立配置地下进风系统的间接空冷塔数值计算模型,得到间接空冷塔的空气流场特性和热力特性。基于凝汽器和空冷散热器协同调节、相互制约的作用机制,采用机理模型和数值模拟相结合的方法建立排汽压力的计算模型,在此基础上计算地下进风系统的热经济性。结果表明,在4 m/s风速下,虽然迎风扇段空气流量减少14.5%,热负荷降低12.4%,但侧风扇段和背风扇段冷却空气量分别增加46.0%、8.0%,热负荷分别提升30.9%、3.2%。在高风速工况下,地下进风系统削弱环境风对排汽压力的影响,具有抵御自然大风的能力。某660 MW间接空冷机组,采用地下进风系统全年可节约标煤9554.3 t,节省燃料费1094.0万元。

深井自然风压数值模拟及计算模型研究

对处于基建期的鑫汇金矿自然风压进行现场测试,获取夏季及冬季自然风压数值。采用fluent软件进行建模,用现场测得的自然风压数据验证模型的可靠性。在此基础上,通过正交模拟实验探究入风温度、热源热量、地温梯度、相对湿度对深井自然风压的影响。极差分析结果表明,各因素对深井自然风压的影响程度为:冬季入风温度>热源热量>地温梯度>相对湿度;夏季热源热量>入风温度>地温梯度>相对湿度。利用SPSS软件对正交实验数据进行拟合,并结合现场实测数据,建立了鑫汇金矿深井自然风压计算模型,为鑫汇金矿深部矿区通风系统的设计和风机选型提供了理论依据。

并列切角方柱风致干扰效应的大涡模拟研究

针对并列切角高层建筑间的干扰影响问题,本文采用大涡模拟方法研究雷诺数22 000的均匀流场下并列切角(切角率10%)方柱的干扰效应。基于模型的网格收敛性分析及模型准确性验证,对比分析不同间距比下并列切角方柱的气动干扰效应和流场分布,并探寻风压干扰效应的影响规律和形成机理。结果表明:对于并列切角方柱,平均阻力系数主要呈放大效应,脉动升力系数主要呈减小效应。在并列切角方柱处于小间距(B/L=1.2)时,由于风与壁面的相互作用,产生风压力,风压力与方柱表面力叠加,对正压区域产生加强效果,表现为放大效应,对负压区域进行削弱,出现减小效应;当B/L=1.5时,结构干扰最剧烈,其中相邻立面后流场的切角处放大效明显,干扰因子最大值为2.58;当B/L≥4.0时,除相邻立面外的其他立面与切角干扰效应趋于消失;当B/L=8.0时,相邻立面仍然存在28%的放大效应。

综掘巷道大风量双压风筒下长压短抽除尘效果的模拟研究

煤矿井下大风量双压风筒综掘巷道具有产尘强度大、粉尘分散度高、巷道风速大等特点,严重威胁作业人员身心健康和矿井安全生产。为降低大风量综掘巷道粉尘浓度,基于CFD数值模拟软件建立了双压风筒综掘巷道物理结构,采用DPM模型,重点研究了单抽双压式通风下抽风筒入风口与巷道迎头之间的距离对掘进工作面粉尘运移规律的影响,分析了大风量双压风筒下长压短抽通风方式对司机位置作业环境的影响。结果表明:保持双压风筒出口距巷道迎头为4、5 m,压入风量为1 200 m^(3)/min条件下,当抽风筒入口与巷道迎头之间的距离为8 m时,司机位置粉尘浓度为30~90 mg/m^(3),作业环境最佳。

基于聚光集热和脉动风压的定日镜群模拟研究

太阳辐射量和风荷载会直接影响光热电站的持续发电量。文章根据新疆哈密地区中电淖毛湖光热电站的实际环境情况,建立定日镜群的三维数值模型,对不同季节太阳辐射和迎风仰角下镜群的受热情况及流场特性开展数值模拟,分析获得风在不同入射角下镜面耀斑分布情况和脉动风压系数。结果表明:模拟所得镜群阻力系数和升力系数与相关研究结果较为吻合,验证了所建模型的有效性;不同季节下耀斑的分布规律较为相似,主要取决于太阳方向角的变化;随着风入射角的增大,镜群的尾流区域呈先减小后增大趋势;由于定日镜镜群中的尾流可有效抑制风压,结合镜群的排布方式保证内部的稳定性,其中,正五边形定日镜的中心处保持较低的脉动风压,极大提高了镜面受力均衡性。

外挂物气动特性的数值模拟和风洞试验

根据外挂物高、低速风洞测压试验数据和CFD数值仿真模拟,获得了左右侧机翼下外挂物的气动特性。基于“三层次”网格生成技术,利用有限体积法求解带有湍流模型的Navier-Stokes方程,对外挂物扰流流场进行数值模拟,结合高、低速测压风洞试验,验证了研究手段的有效性,分析了不同气动力系数随攻角、侧滑角及马赫数的变化情况。结果表明:高、低速下外挂物升力系数受攻角影响的规律一致;在正侧滑时,机身的遮挡对右机翼下外挂物的侧向力系数和偏航力矩系数的影响较大。

悬挑体育场罩棚风荷载数值模拟

使用Realizable k-ε湍流模型对悬挑体育场罩棚表面风荷载特性进行CFD数值模拟研究,详细考察体育场罩棚表面风向角对净风压系数、体型系数和平均风压系数分布影响规律,为此结构表面风荷载设计取值提供依据。计算结果表明:体育场罩棚上表面主要是受到风吸力作用,在罩棚前檐和两个角部区域风压系数浮动较大,比如在180°风向角罩棚两个角部区域风压系数为-0.5~-3.5。由于结构造型需要,罩棚顶部凸出的肋对风荷载的影响大,其产生原因为在顶部凸起肋后形成小漩涡,风压系数变化剧烈,90°风向时,来流迎风面第一个肋后面风压系数为-1.5~1.1。由于来流在罩棚后檐出现分离,在180°风向罩棚结构上下表面出现“上吸下压”现象,罩棚受到向上升力。

大跨度体育场风效应的大涡模拟及风洞实验研究

文章运用大涡模拟(large eddy simulation,LES)湍流模型对天长市某大跨度体育场风效应进行数值风洞模拟,得到体育场平均风压、脉动风压分布规律及风荷载时程,利用阵风荷载因子法计算体育场屋盖的风振系数及等效静力风荷载,与风洞实验结果开展对比研究。结果表明,数值模拟评估的体育场表面风压分布规律与风洞实验结果吻合较好,能够较好地反映大跨度体育场表面风压分布情况,2种方法计算得到的风振系数及等效静力风荷载也基本相同,说明大涡模拟技术能有效预测大跨度空间结构风荷载。研究结果可为大跨度体育场的抗风设计提供技术参考。

基于CFD的光伏面板风荷载体型系数研究

风荷载体型系数是计算太阳能光伏面板所受风荷载大小的重要参数。本文基于流体力学分析平台Flu⁃ent,采用雷诺时平均法开展不同风向角和不同安装倾角工况下光伏面板风压分布规律、风速矢量及其风荷载体型系数的研究,并将模拟结果与各国规范进行对比。计算结果表明:风向角和安装倾角变化均对光伏面板所受风荷载的大小具有显著影响;光伏面板表面正压、负压的递减方向与气流方向一致;面板上、下表面迎风侧边缘处存在较大的压力差,易造成光伏面板风致损坏;根据CFD数值模拟结果以及与各国规范对比分析,提出了不同安装倾角和不同风向角工况下光伏面板风荷载体型系数建议值。研究成果可为太阳能光伏组件的抗风设计提供一定的参考依据。

不同宽度比串列方柱流场和气动力特性研究

为研究干扰条件下串列方柱的风压特性及其流场机理,文中采用大涡模拟方法,探究不同宽度比施扰建筑的干扰下,受扰建筑周围流场和气动力的影响,并分析不同模型在雷诺数为22000,间距比为2.5时的气动力系数、平均风压系数以及流场分布特性。结果表明两方柱的平均阻力方向相反,脉动阻力系数呈现先减后增,再减再增的规律;迎风面和背风面均表现为风吸力,侧立面有部分区域表现为风压力,平均风压系数极值随着宽度比的增加而增大;随着宽度比的增加,上游方柱剪切层的宽度增大。在5种不同宽度比下的干扰效应研究中,得出的结论是当宽度比为1.4时,遮挡效应最为明显。