风致大型卡氏天线静态和动态响应分析

The effect of wind load on the high frequency observation is unignorable. However,it is always diffcult to study the antenna structure response under wind load in the field of astronomical technology. Adopting the methods of numerical simulation combining to theory and experiment, the two key problems of the effects of average wind on surface accuracy and fluctuating wind on pointing accuracy were studied.Firstly, the measures of turbulent model selection and network optimization were taken to accuratly calculated the wind pressure and deformation of the primary reflector surface using finite element software, which were testified by the experiment of the out of focus holography. Then, the model of wind speed in the domain was established based on modified Davenport power spectral density function. The dynamic responses of the structure were simulated when the fluctuating wind loads were applied on the model.Simultaneously, adopting the method of enviromental random excitation, the characteristics of structure vibration were obtained exactly based on the accelerometers.The vibrations of the sub-reflector and legs caused by the wind load were comprehensively analized by both experiment and numerical simulation. Finally,based on available analysis methods and results,the controlling method of the deformations of primary reflector surface was established and the reinforcing scheme of legs was determined.The project hopes to make a breakthrough in experimental research of the wind-induced static and dynamic response of large-scale Cassegrain antenna and give a basis for analysis and control of antenna accuracy.

风载荷对天线高频段观测的影响不容忽视，而天线结构的风响应问题一直是天文技术领域研究的难点，本项目将采用数值模拟、理论和实验相结合的方法，紧紧围绕平均风致主反射面精度变化和脉动风致天线指向精度变化两个核心问题展开研究。首先，借助有限元软件，通过湍流模型选择和网格优化等措施，实现主反射面风压分布和变形的精确计算，并利用偏焦全息法进行方法有效性的实验验证。然后，建立基于修正的Davenport功率谱密度函数的风速时程表达式，将其作为载荷模拟计算结构动态响应；同时，采用环境随机激励法，由加速度传感器测量获得准确的结构振动特性，通过实验和数值模拟综合分析风致副反射面和撑腿的振动。最后，基于已有的分析方法和结果，确立主反射面变形的控制策略，确定撑腿的加固方案。本项目争取在风致大型卡氏天线结构静态和动态响应的实验研究方面取得一定的突破，为天线结构的精度分析和控制提供依据。

本项目以天马望远镜（TM65m）为研究对象，采用数值模拟和实验相结合的方法，紧紧围绕平均风和脉动风致主面面型精度和天线指向精度变化两个核心问题展开研究。首先对观测站实测的风速风向数据做了统计分析，得10m高度处10min 时距平均风速小于4 m/s 的占比超过80%，主导风向为北-西北方向。然后，通过将倾斜仪实测结果与数值模拟结果进行对比，验证了模拟的有效性，并进一步分析了在不同迎风姿态、不同风速下天线结构的变形，以及天线面形精度和指向精度的变化。结果表明，在4 m/s平均风速下，风荷载对天线指向精度，尤其是俯仰角指向精度的影响较大（最大值9.5arcsec），对面型精度的影响较小（最大值0.032mm）；在弹性范围内，天线面型精度和指向精度与风速间均为二次关系。另外，基于CFD大涡模拟方法，计算得到TM65m反射面的风压时程，将其作为荷载施加到有限元模型上，进行非线性动力时程分析，分析结果显示结构的位移响应主要集中在第一阶自振频率附近，进一步分析得脉动风对面型精度和指向精度的影响约是平均风作用的3倍。最后，在TM65m上搭建结构振动测量系统，测量数据显示副面和撑腿振动具有一致性，进一步将利用该系统于探究脉动风致天线指向精度变化的规律。建立的静动态分析和测量方法及分析结果为天线面型精度和指向精度的分析和控制提供依据，为观测计划高效地制定和实施提供参考。