【作者】 林巍；

【导师】 楼文娟；

【作者基本信息】 浙江大学 ， 结构工程， 2012， 硕士

【摘要】 在特殊的气象条件下,输电导线可能在其迎风面结冰,具有翼形的某些特征,从而使导线发生大幅、低频的自激振动,即舞动。近年来我国电网规模发展迅速,恶劣气候频繁出现,输电线路的覆冰和积雪以及由此衍生的导线舞动已经严重威胁着电力及通信网络的安全运行。覆冰导线的气动力参数是舞动试验研究及计算分析的关键因素,虽然已有一些试验结果,但由于覆冰的随机性和多样性,数据仍十分缺乏,积累更多覆冰导线的气动力参数具有重要的意义。本文详细回顾了国内外有关覆冰导线的气动力试验研究,提出了存在的缺点与不足。在此基础上通过风洞试验及CFD数值模拟方法研究了不同厚度新月形覆冰和D形覆冰截面单导线及分裂导线的气动力特性。风洞试验方面：制作了刚性节段模型,通过高频测力天平试验研究了D形和4种新月形覆冰厚度输电导线的气动力特性。设计了考虑流场二维特性和风洞的边界层效应的试验装置,获得了各覆冰截面单导线和分裂导线子导线在均匀流、5%均匀湍流和13%均匀湍流3种流场中各风攻角下的气动力特性,研究了气动力系数对攻角的变化规律,以及湍流度对气动力特性的影响。比较了单导线与二、四、六分裂导线之间气动力特性的区别与联系。根据Den Hartog和Nigol舞动理论分别计算了各种工况下覆冰导线可能发生舞动的风攻角范围。CFD数值模拟方面：通过CFD数值模拟方法,对雷诺数为3900的经典圆柱绕流问题进行了非定常计算,详细研究了近壁面网格及展向长度对结果的影响。在此基础上,通过k-ωSST湍流模型计算了新月形薄覆冰单导线及四分裂导线的气动三分力系数,研究了展向长度、网格尺寸等参数对计算结果的影响,通过不同工况下数值模拟结果与试验结果的对比,验证了薄覆冰导线可行的数值模型。由于条件所限,风洞试验往往只得到分裂导线的整体气动力,通过数值模拟方法则明确了分裂导线各子导线的气动力系数对整体扭转系数的贡献。本文的成果丰富了现有覆冰导线的气动力参数,为深入进行覆冰导线舞动试验及仿真提供了宝贵的参数并为进一步精确计算其他覆冰形状的气动力系数提供了参考。更多还原

【Abstract】 In special weather conditions, transmission lines may be iced in windward side, with some features of the wing. It may cause a large amplitude and low-frequency self-excited vibration, which is so called galloping. In recent years, with the rapid development of the power systems and frequent occurrence of the extreme weather, the galloping due to the icing and snowing of the transmission lines has been a serious threat to the security of the electricity and communication network operations. The aerodynamic parameter of the iced conductor is a key factor that affects the calculation and analysis for dancing. Although there have been some test results of the aerodynamic parameter, due to the randomness and variability of the accreted shape, the data for anti-galloping design has not been obtained enough and there is a great value to accumulate more aerodynamic parameters of iced conductors.In this study, the domestic and foreign wind tunnel test researches on aerodynamic characteristics of iced conductors were reviewed in detail, and the shortcomings and inadequacies were proposed. Then the aerodynamic characteristics of single and multi-bundled conductors with difference thickness crescent-shaped and D-shaped were studied by wind tunnel test and numerical simulation (CFD). The main contents of the wind tunnel test and numerical study were as follows:Wind tunnel test:Rigid segment models of D-shaped and 4 kinds of crescent-shaped were made, and the aerodynamic characteristics were then measured by high-frequency force balance. A wind tunnel test device taking the two-dimensional flow characteristics and the effect of boundary layer into account was designed. Under the homogeneous turbulence of 0%,5% and 13%, the aerodynamic force coefficients of single and bundled conductors with different ice section were obtained, and the effects of turbulence on the aerodynamics were discussed. Subsequently, the relationships between the aerodynamic characteristics of single conductors and those of bundled conductors were described. Furthermore, based on the Den Hartog and Nigol’s mechanisms of galloping, the wind angle ranges sensitive to galloping were analyzed.Numerical study. Wind flow around a cylinder with Reynolds number of 3900 was simulated adopting LES. The effects of near-wall grids and span-wise length on the numerical result were studied in detail. The aerodynamic coefficients of single and 4-bundled conductors with thin crescent-shaped ice were then calculated by k-ωSST turbulence model. The parameters such as span-wise length, grid size and turbulence model, which affect the calculation result were discussed. By comparisons of numerical results with those of corresponding experiments, the appropriate numerical model was verified. While the wind tunnel test is only able to obtain the overall moment coefficients of 4-bundled conductors, numerical study is capable of quantifying three parts of torsion on the bundle conductors respectively.The results of this paper enrich the current data of aerodynamic characteristics for iced conductors. It can provide valuable parameters for studying on galloping test and simulation. Moreover, it can provide a reference for accurately calculating aerodynamic coefficients of other ice-shaped conductors.更多还原