Numerical Investigation of the Effects of Wind Tunnel Model Vibrations on the Measured Aerodynamic Properties of Airfoils and Wings

This paper presents a numerical prediction of the unsteady flow field around oscillating airfoils at high angles of attack by solving unsteady Reynolds-averaged Navier-Stokes equations with SST turbulence model in order to simulate the effects of wind tunnel model vibrations on the aerodynamic properties of airfoils,especially high-aspect-ratio wings in a wind tunnel.The effects of the phase lagging between different modes of oscillations,i.e.,the airfoil plunging oscillation mode,the pitching oscillation mode,and the forward-backward oscillation mode,are also studied.It is shown that the vibrations (oscillations) of airfoils can cause the unsteady shedding of large-size separated vortex to precede the stationary stall incidence,hence lead to a stall onset at some earlier (lower) incidence than that in the steady sense.The different phase lagging has different effect on the flow field.When the pitching oscillation mode has small phase lagging behind the plunging oscillation mode,the effect of vibrations is large.Besides,if the amplitude of the oscillations is large enough,and the different modes of vibrations match or combine appropriately,the unsteady stall may occur 2° earlier in angle of attack than the case where airfoils keep stationary.

Evaluation of a Micro-scale Wind Model's Performance over Realistic Building Clusters Using Wind Tunnel Experiments

The simulation performance over complex building clusters of a wind simulation model（Wind Information Field Fast Analysis model, WIFFA） in a micro-scale air pollutant dispersion model system（Urban Microscale Air Pollution dispersion Simulation model, UMAPS） is evaluated using various wind tunnel experimental data including the CEDVAL（Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models） wind tunnel experiment data and the NJU-FZ experiment data（Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data）. The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier–Stokes equations, and can produce very high-resolution（1–5 m） wind fields of a complex neighborhood scale urban building canopy（～ 1 km ×1km） in less than 3 min when run on a personal computer.

Aeroelastic modeling of wind loading on a cable-net supported glass wall

Wind loading study on a cable-net supported glass wall is conducted by means of wind tunnel tests. An equiva- lent aeroelastic model is designed and constructed. Response of displacements of the wall is measured and analyzed. In order to design a glass wall under wind loading, the ＂wind- vibration factor＂ is estimated and discussed. In fact, the mech- anism of wind acting on the wall is commonly known not only as positive pressure, but also as negative pressure caused by the flow separation on the corners of the building. Due to the diffidence in the mechanism of wind acting, two typi- cal response cases are classified. The results show that the dynamic response of the structure caused by the negative pressure is stronger than that of the positive pressure case. To determine the aerodynamic wind loading on a flexible part of structure on a building, wind tunnel study may be useful and play an important role.

Wind tunnel study on wind-induced vibration of middle pylon of Taizhou Bridge

Full aero-elastic model tests are carried out to investigate wind-induced vibration of middle steel pylon of Taizhou Bridge. Model of the pylon under different construction periods is tested in both uniform and turbulent flow field. And the yaw angle of wind changes from transverse to longitudinal. Through full aero-elastic model testing, wind-induced vibration is checked, which includes vortex resonance, buffeting and galloping. Vortex resonance is observed and further studies are carried out by changing damping ratio. Based on wind tunnel testing results, wind-resistance of middle pylon is evaluated and some suggestions are given for middle pylon's construction.

Evolution of crescent-shaped sand dune under the influence of injected sand flux:scaling law and wind tunnel experiment

This paper studies the evolution of crescent-shaped dune under the influence of injected flux. A scaling law and a wind tunnel experiment are carried out for comparison. The experiment incorporates a novel image processing algorithm to recover the evolutionary process. The theoretical and experimental results agree well in the middle stage of dune evolution, but deviate from each other in the initial and final stages, suggesting that the crescent-shaped dune evolution is intrinsically scale-variant and that the crescent shape breaks down under unsaturated condition.

Aerodynamic coefficient of vehicle-bridge system by wind tunnel test

The changes of three components of aerodynamic force were discussed with the attack angle conversion for three kinds of section models.Based on the project of Shanghai Yangtze River Bridge,the wind tunnel test was conducted to obtain its three components of aerodynamic force including 75 conditions of the construction stage,the bridge without vehicles and the bridge with vehicles from-12 degrees to +12 degrees.For the bridge with vehicles,the drag force coefficient and the absolute value of both lift coefficient and moment coefficient were decreased by the vehicles.The test result shows that the bridge railing and vehicles have much influence on the three components of aerodynamic force of the vehicle-bridge system for Shanghai Yangtze River Bridge.

Wind tunnel study of aerodynamic wind loading on middle pylon of Taizhou Bridge

Segment sectional model tests are carried out to investigate the wind loading on middle pylon of Taizhou Bridge, which has complicated three-dimensional flow due to its feature of double columns. Through the force measuring tests, aerodynamic force coefficients of every segment of the pylon columns have been obtained. It is found that the tested aerodynamic force coefficients are much smaller than those given by codes. The interference effects of aerodynamic force coefficients between columns of pylon are discussed. The results show that the interference effect is the most evident when the yaw angle is about 30 ° from transverse direction. This kind of interference effect can be described as diminutions in transverse aerodynamic force coefficients and magnifications in longitudinal aerodynamic force coefficients of downstream columns.

基于气弹模型风洞试验的高耸桅杆风振响应特性

为了探究高耸桅杆结构风振响应特性,采用刚性节段加连接棒法制作了356 m高桅杆的气弹模型,通过风洞试验研究了桅杆结构的位移响应高度分布特征和模态参与特性,并分析了风速和风向的影响.结果表明,桅杆结构的位移响应随高度呈非线性变化,其最大平均和脉动响应均出现在顶部2层纤绳锚固点间的中间部位.桅杆结构的横风向响应基本与顺风向相当.风向改变对平均位移有一定影响,对脉动无明显影响.结构顺、横风向风振响应中前三阶模态振动能量具有相近量级,且风速变化会对桅杆结构的模态频率产生一定影响.结构气动阻尼均为正值,且随风速增加而增大.桅杆结构的顺风向风振系数除底部外,其他高度均要显著低于规范值.风速和风向的改变对桅杆中、上部的风振系数影响较小,仅在底部影响较为明显.

边界层和压力滞后对翼型动态失速性能的影响

为优化动态失速模型经验常数,提升动态失速发生时翼型气动性能预测精度,该文基于B-L动态失速模型,结合内蒙古工业大学风能太阳能利用技术教育部重点实验室风洞实验数据,探究压力滞后及边界层滞后时间常数对翼型动态失速性能的影响。主要结论如下:压力滞后与边界层滞后时间常数对动态升力系数的影响较大且与平均攻角有关。当平均攻角相对较小且气流处于附着流动与分离流动之间时,适当减小时间常数可使动态失速模型计算结果更接近实验值;当平均攻角相对较大,气流处于分离流动与完全分离流动时,可适当增大时间常数值。压力滞后与边界层滞后时间常数对动态阻力系数的影响不显著。动态升力系数仅在攻角逐渐减小的完全分离流动过程中,随着边界层滞后时间常数的增大而减小。

超高桥塔的气弹模型风洞试验及其等效静力风荷载

为研究超高桥塔的气弹模型风洞试验方法及其等效静力风荷载,根据某实际工程中的超高桥塔建立了有限元模型,进行了动力特性计算,进而设计了相应的气弹模型,并开展了风洞试验。在此基础上,开展了超高桥塔风致振动的非线性时程计算,并基于阵风荷载因子法,对比了以位移、内力和应力为单一目标的超高桥塔的等效静力风荷载。结果表明:斜风作用下的桥塔风致振动比较显著,其影响随着风速的增大而愈加明显;当风向角为75°~90°时,超高桥塔将在风速为35~50 m·s^(-1)的区间发生顺桥向的侧弯涡振,但幅值较小;基于应力的阵风荷载因子比基于位移或内力的阵风荷载因子更加稳定,这使得基于应力的等效静力风荷载要优于基于位移或内力的等效静力风荷载,比较适合于超高桥塔。

典型峡谷Ⅴ型地貌下桥址区风特性

为得到山区峡谷典型Ⅴ型地形下的桥梁抗风设计的关键风特性参数,通过“数值风洞试验”建立模型,以实桥为工程背景构建三维地形网格,基于3种典型湍流模型和流体壁面粗糙度对桥位的风场特性进行分析,选取最优湍流模型和流体壁面粗糙度对该地形桥位处的风场特性进行分析;围绕两个影响桥址区风特性的地形参数(山体高度和夹角),阐明Ⅴ型峡谷地形下风特性参数的变化规律,并与现行规范进行对比,推算桥面设计基准风速。结果表明:该Ⅴ型峡谷地形的最佳湍流模型和流体壁面粗糙度分别为RNG k-ε和20 m;随着山体高度及山体夹角两参数的变化,风速增加幅度分别为2.37%~12.56%和1.24%~6.98%;山体高度及山体夹角两变参数下,梯度风高度分别为700 m和800 m左右;实际湍流强度大于规范中四类地表规范值,在离地高度40 m范围内,湍流强度更接近于D类地表。实际Ⅴ型峡谷桥址区不能简单按规范归为C类或D类地形,在设计风参数计算时应综合考虑规范和经验公式,还可借助模拟手段来提高其准确性。

柔性光伏系统颤振性能的节段模型试验研究

柔性光伏支架的频率低、质量轻,极易在风荷载作用下发生大幅振动。以某实际柔性光伏项目为工程背景,借鉴桥梁抗风的研究经验,对该柔性光伏支架的颤振性能进行研究。首先,考虑严格的相似比关系,设计并制作了弹性悬挂节段模型系统,并对其动力特性进行了测试;然后,进行不同光伏组件倾角(-39°~+39°)下的弹性悬挂节段模型测振风洞试验,研究光伏组件风致响应随风速的变化规律,得到各倾角下柔性光伏节段模型的颤振临界风速值,探讨2种气动措施对提高柔性光伏支架颤振稳定性的效果。结果表明:在0°~39°的正倾角工况下,柔性光伏支架的颤振临界风速随光伏组件倾角的增大,呈现先减小后增大的趋势,最小颤振临界风速出现在12°~21°光伏组件倾角范围内,折算成实际风速为9.6m/s;在-39°~0°的负倾角工况下,颤振临界风速随光伏组件倾角的增大,也呈现先减小后增大的趋势,最小颤振临界风速出现在-21°~-12°光伏组件倾角范围内,折算成实际风速为10.1m/s;设置中央稳定板的气动措施难以有效提高柔性光伏支架的颤振临界风速。

胶囊形气膜结构风致气弹响应及风振系数研究

针对1/3矢跨比胶囊形气膜结构进行了气弹模型风洞试验,研究了结构的风致气弹响应变化规律,并给出了可供设计参考的风振系数。研究发现:结构平均变形呈迎风面凹陷,顶部隆起,横风向向外凸出的趋势,且这种变形趋势随着内压减小和风速增大越来越明显。0°风向角时的平均变形和振幅大于45°风向角时的平均变形和振幅大于90°风向角时的平均变形和振幅,结构合位移均值的极值出现在迎风面与顶面中心点;0°和45°风向角下,顶点竖向振幅>顺风向振幅>横风向振幅,结构以1阶模态振动为主;90°风向角下,顶点横风向振幅大于其他两个方向,结构以1阶和2阶模态叠加振动为主。各工况下结构的内压均有不同程度的减小。最后给出了考虑流固耦合效应的响应风振系数。

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。

大跨PK断面钢箱梁斜拉桥涡振性能及优化措施研究

红莲大桥主桥为主跨580 m的双塔斜拉桥,中跨主梁采用PK断面钢箱梁,该类主梁断面易发生涡振,需对其涡振性能及抑振措施进行研究。基于该桥有限元动力特性分析结果,制作PK断面钢箱梁1∶60缩尺比节段模型进行测振风洞试验,研究桥梁原始设计断面主梁的涡振性能,讨论增加结构阻尼比(增加至0.010和0.027)措施的涡振抑振效果,并对增设稳定板、水平导流板、部分封闭桥面栏杆等不同气动优化措施及组合对主梁涡振性能的影响进行分析。结果表明:原始设计PK断面钢箱梁的涡振振幅明显超过规范限值;增大结构阻尼比虽然可以有效抑制涡振响应,但阻尼比增加至0.027时竖弯涡振振幅仍然显著;在桥面检修栏杆上缘外挑1.6 m宽水平导流板可将涡振振幅降低到可忽略的水平;采用在检修栏杆上缘外挑1.1 m宽水平导流板、优化桥面燃气管道位置、调整防撞护栏下部封闭高度为0.42 m,或移除检修道栏杆底座、错列布置封闭检修道栏杆和防撞护栏等组合措施,虽不足以完全抑制涡振的发生,但可将涡振振幅控制至明显小于规范限值。

热风洞温度系统的无模型自适应级联控制

热风洞能够为高温热电偶动态标定和航空发动机叶片热强度测试等应用场景提供均匀且稳定的温度场,如何对热风洞所产生的热气流进行宽温范围的温度控制是一个难点。为此,建立了热风洞燃油流量和燃烧室温度的数学模型;设计了一种内环为增量式比例积分微分(PID)和外环为无模型自适应控制(MFAC)的级联控制方法,增量式PID控制器控制燃油流量,MFAC控制器控制燃烧室温度,实现了对燃烧室温度的有效控制;进行了不同目标温度的数值模拟和试验研究,并与FuzzyPID-PID级联控制方案和传统的级联PID控制方案进行了对比测试。试验结果确认了所提控制方案的可行性与优越性。

风洞模型-支撑系统多维振动特性辨识与试验研究

针对风洞模型-支撑系统振动特性不明导致控制有效性差的问题,首先基于风洞模型-支撑系统的结构与原理,设计了系统振动特性辨识整体方案;其次建立了系统的等效动力学模型,通过引入动刚度对系统的俯仰、偏航维度振动特性进行了理论分析;进而提出了“正弦扫频-频谱细化-频响函数”振动特性辨识方法,并依据辨识结果建立了振动状态估计模型,将其引入控制闭环形成了基于辨识的控制方法;最后开展了脉冲响应试验与锤击试验,并对比了传统方法与基于辨识的控制方法的抑振效果。试验结果表明:俯仰、偏航维度频率响应辨识结果的均方根误差分别为0.084 0 g/V、0.007 5 g/V;且基于辨识的控制方法相较于传统控制方法将俯仰、偏航维度的等效阻尼比分别提升了1.48倍、3.00倍,具有明显优势。

升力体缝隙模型红外测热试验及分析

针对升力体缝隙模型在中国空气动力研究与发展中心的Φ0.3 m高超声速低密度风洞中开展了红外测热试验,试验马赫数12、总温668 K、总压4.731 MPa、攻角0°和35°,获取了模型的红外热图结果,并开展了相应的数值仿真分析。在此基础上,研究了选取不同帧次的红外热图进行数据处理对热流密度结果的影响,分析了缝隙干扰引起的热流密度增量。结果表明:投放后模型抖动对数据处理存在明显影响,建议在数据处理中采用模型投放稳定后(约1.2 s)的红外热图结果;“T”字型缝干扰区的热流密度增量需要引起重视,攻角35°情况下的峰值热流密度能达到无缝隙时热流密度的8倍以上;红外测热试验数据与CFD数据吻合较好,两者仅在很小的峰值干扰区域存在差异。下一步需要在CFD建模倒角处理、红外方案优化等方面开展工作。

大型抽水蓄能电站长直型隧洞风尘迁移规律研究

抽水蓄能电站地下洞室群施工存在通风难度大、风尘迁移变化规律无显著特征等难题,采用DPM气固两相流模型,针对地下洞室群中不同坡度的长直型隧洞进行数值试验研究,重点揭示了典型隧洞在不同施工条件下的风尘迁移规律及小粒径沉降粉尘分布特征。研究表明:不同区域粉尘质量浓度随风机风速的增大呈下降趋势,当风速增至21 m/s时开始升高;掌子面附近区域粉尘质量浓度随供风距离的增大呈上升趋势,当供风距离大于25 m时,风机风速不再满足隧洞内通风要求;掌子面附近区域粉尘质量浓度随隧洞坡度的增大呈显著上升趋势,通风管附近出现明显的粉尘空白带;小粒径沉降粉尘分布特征由通风管位置决定,沉降粉尘颗粒最多处位于通风管出口与掌子面之间,粒径分布较广,呈正态分布规律,在通风管出口正后方处急剧下降,并沿隧洞出口方向数量逐渐减少,平均粒径逐渐减小;流出洞外的粉尘颗粒平均粒径偏小。本研究可为抽水蓄能电站地下洞室群整体施工设计提供参考。

基于多项式响应面MDOE的低速风洞试验方法研究

现有的基于各类统计模型的现代试验设计(MDOE)方法存在计算量大、建模较复杂导致整体风洞试验效率下降的不足。针对这一问题,本文提出一种将多项式响应面模型与现代试验设计相结合的优化设计方法。采用中心复合设计在自变量区间中划分试验点并进行风洞试验获取气动力,利用最小二乘法确定多项式待定系数,构建响应面模型,并进行方差分析及显著性检验,最后选取了5个传统单变量(OFAT)方法试验点检验响应面模型的拟合精度。结果表明,与传统单变量风洞试验方法相比,本文提出的基于多项式响应面MDOE的低速风洞试验方法具有建模容易、计算量较小、预测校准的优点,可使试验样本点减少50%左右,能够有效提升风洞试验效率。