射电天文研究室知识库

天线面板在长时间的日照作用下,会因为热作用产生变形,了解天线面板的热变形,关键在于确定面板的温度场分布。在日照作用下,同样考虑天线自身的遮挡,其面板热分布显得比较复杂,难以确定。基于ASHRAE晴空模型,结合北京晴空模型的系数迭代回归公式,重点考虑了天线面板在夏至日受太阳辐射、与空气对流换热以及周围环境长波辐射等条件下的热流变化情况,利用有限元分析软件对天线面板在该天的温度场进行了数值模拟,给出了面板温度随时间的变化规律,有助于更好的了解天线面板变形和天线指向的校准。

Deformation of the dish of a radio antenna due to longtime sunshine can severely affect the pointing accuracy of the antenna． A key problem for understanding antenna thermal deformation is to determine temperature distributions on the dish surface． Calculations of temperature distributions on a dish surface are not easy，as a time-dependent direction to the sun and the screening of sunlight by the dish itself need to be taken into account． In this paper we present our results of numerical simulations of temperature distributions on the dish surface of a 25m radio antenna based on the ASHＲAE clear-sky model． Our simulations incorporate the iterative-regression formula of coefficients from the Beijing clear-sky model． In the simulations we mainly consider three factors in June 21st，which are the change of sunlight irradiation on the dish surface，convectional heat exchange with ambient air，and environmental long-wavelength radiation． The simulations were carried out using the ANSYS software package for finite-element modeling． We finally present variations of antenna temperatures，which should be helpful for better understanding thermal deformation of the dish of a radio antenna and effective calibration of antenna pointing．