群集建筑中大跨裙摆屋盖风荷载特性的数值模拟研究

以苏州太平金融大厦为工程背景,针对其大跨裙摆屋盖的风荷载作用,首先采用RNG k-ε模型模拟分析了其平均风压分布规律,以及风向变化对屋盖表面风荷载体型系数的影响;其次,引入干扰因子IF,探讨了周边建筑对大跨裙摆屋盖风荷载的气动干扰作用。结果表明:0°风向下,走廊上方屋盖两侧区域出现“上吸下顶”的叠加作用;90°风向下屋盖北侧飘带末端区域受到狭道风效应出现正压集中现象;风向变化对大跨裙摆屋盖的风荷载体型系数分布影响较大;且周围建筑物对大跨裙摆屋盖的气动干扰效应明显,主要表现为风压“遮挡效应”,而局部区域表现为风压“放大效应”。     

An experimental investigation into non-linear wave loading on horizontal axis tidal turbines

Tidal turbines are subject to large hydrodynamic loads from combinations of currents and waves, which contribute significantly to fatigue, extreme loading and power flow requirements. Physical model testing enables these loads and power fluctuations to be assessed and understood in a controlled and repeatable environment. In this work, a 1:15 scale tidal turbine model is utilised to further the fundamental understanding of the influence of waves on tidal turbines. A wide range of regular waves are generated in both following-current and opposing-current conditions. Wave frequencies range from 0.31 Hz to 0.55 Hz & wave heights from 0.025 m to 0.37 m in a fixed 0.81 m/s current velocity. Waves are selected and programmed specifically to facilitate frequency domain analysis, and techniques are employed to isolate the effect of non-linear waves on turbine power and thrust.Results demonstrate that wave action induces large variations in turbine power and thrust compared to current only conditions. For the range of conditions tested, peak values of thrust and power exceed current-only values by between 7%–65% and 13%–160% respectively. These wave-induced fluctuations are shown to increase with wave amplitude and decrease with wave frequency. Following wave conditions exhibit greater variations than opposing for waves with the same wave height and frequency due to the lower associated wavenumbers.A model is developed and presented to aid the understanding of the high-order harmonic response of the turbine to waves, which is further demonstrated using steady state coefficients under assumptions of pseudo-stationarity. This approach is proven to be effective at estimating wave-induced power and thrust fluctuations for the combinations of waves, currents and turbine state tested. The outcome of which shows promise as a rapid design tool that can evaluate the effect of site-specific wave–current conditions on turbine performance.     

一种提高风能利用率的风力发电机控制策略

在变速恒频风力发电机组的各类并网逆变器控制策略中,零d轴电流控制和空间矢量脉宽调制(SVPWM)以能够提高风能利用系数和稳定逆变器输出电压的优势得到了广泛的应用.在理论研究阶段需要对其进行仿真,然而在Matlab/Simulink中并没有可以实现上述功能的并网仿真模型.因此推导了变速恒频风力发电机组及控制策略的数学模型,并在Matlab/Simulink中完成搭建、当风速恒定不变时,对发电系统的运行情况进行了仿真.结果表明,零d轴电流控制与SVPWM的结合,既提高了风能利用系数,又有效地提高了逆变器的输出电压,保证当电网电压升高时不影响发电系统向电网输送功率的效率.     

新型风成像干涉仪温度补偿理论研究

简述了高层大气风场被动式遥感探测的基本原理;论述了新型风成像干涉仪宽场、消色差、温度补偿理论,针对目前国际上采用的风成像干涉仪补偿方法的不足,从理论上进行了分析与讨论,给出了四层介质的优化补偿理论和方案.模拟结果表明,该补偿可完全理想地消去单色光的温差,且复色光的温差补偿要比现有的方法提高1—2个量级.该研究为设计宽场、消色差、温度补偿的新型风成像干涉仪和提高风场探测精度提供了重要的理论依据和实践指导.     

非球对称情况下的恒星风运动方程

本文应用理论物理方法研究处于非平衡态的恒星大气,考虑及辐射压力、快速自转和起潮力的作用,得到非球对称情况下的恒星风运动方程。     

大气边界层模拟的湍流相似

大气边界层的风洞模拟,是目前研究建筑物风载,污染质的大气扩散,以及解决某些环境科学和军事科学中大型课题的重要手段之一。在许多国家,风洞模拟已成为环境部门设计大型工程、林区、厂区和城区规划的主要依据。最初的大气边界层模拟装置,仅考虑形成一定的平均风速廓线,并未考虑到气流的湍流特性。微气象学的研究表明,大气的湍流特性是影响扩散的主要因素。特别是Monin和Obukhov通过大量实测资料提出大气表面层中的相似性理论,成为研究大气扩散的重要依据。从50年代开始,一些研究大气扩散和建筑物风载问题的长实验段风洞相继筹划和建立。其中较著名的有,美国科罗拉多州立大学的1.8米×1.8米×30米的回流式长实验段气      

透平转子的可靠性设计

介绍透平转子的可靠性设计方法。该方法以传统的转子强度和振动的设计方法为基础,把透平转子的静应力、材料静强度、应力幅、尺寸系数、表面加工系数、应力集中系数、材料疲劳极限、热疲劳累积损伤程度、材料低周疲劳程度、蠕变寿命、固有频率、激振力频率、不平衡响应等处理为随机变量,使用机械概率设计法确定转子设计的可靠度。文中给出了透平转子静强度、疲劳强度、热疲劳、蠕变寿命、避开弯曲共振、避开扭转共振和限制不平稳响     

Loss Reduction by Means of Two-Dimensional Roughness Elements on the Suction Surface of a Linear Turbine Rotor Cascade

This paper reports the results of experimental investigations carried out to reduce pressure losses by means of two-dimensional roughness elements (in the form of stainless steel tubes of different diameters). The roughness elements are fixed at various axial stations on the suction surface of 120° turning, 175 mm chord, impulse turbine rotor blades. Flow measurements are carried out at the exit of the cascade at five axial stations, using a five-hole probe operating in non-nulling mode. In addition, the blade surface static pressure distribution is measured. The data from the five-hole probe measurements are used to calculate pressure, velocity and flow angle distributions at the cascade exit and these results are used to calculate mass averaged values and integral parameters such as wake half-width, loss coefficient, etc. The static pressure distribution is altered very little except near the roughness element. The lift coefficient remains almost constant for all configurations and the drag coefficient is reduced for some configurations. The non-dimensional total pressure defects in the wake for all configurations followed Gaussian distribution. A two-dimensional roughness element of 0.6 mm diameter placed at 0.65 chord on the suction surface showed an appreciable reduction in pressure losses.     

基于遗传算法的透平级多目标优化设计

本文发展并完善了一种基于非受控解的排序、基于共享机制的小生境技术和交配约束的多目标遗传算法,在一元热力设计基础上,对一个透平级取实际压力与给定压力的差值和级的作功能力为目标函数进行了优化。算例表明该算法具有同时捕获—组解的能力,对于解决多目标优化问题具有很强的适应性和合理的优化结果,是一种有效的多目标优化方法。     

受控结构风振响应分析的广义虚拟激励法

基于复模态分析和虚拟激励法．提出了用于具有密集频率和非经典阻尼受控结构风振响应分析的广义虚拟激励法。该法可以考虑任意风谱和空间相关性以及模态耦合效应,且计算效率很高。不同于SRSS法．该算法包含了全部参振模态之间和全部激励点之间的相关性．在理论上是精确解。