Research And Simulation Of The Wind Field Environment For The 110-meter Aperture QiTai Radio Telescope Site

The Xinjiang Astronomical Observatory intends to build the 110 m aperture radio telescope(QTT)in Qitai,Xinjiang,which will become the largest fully mobile radio telescope in the world.Its working frequency is from 150 MHz to 115 GHz,and the pointing accuracy requirement is up to 2.5 arcs.The higher the performance requirements of the radio telescope,the more complex the antenna structure design,and the more prominent the influence of wind load on the telescope pointing accuracy,especially in the high frequency band.The accurate information of wind field characteristic can guarantee the stiffness and strength of the antenna structure in design and improve the effective observation time of telescope during the observation.Therefore,it is of great significance and practical value to study the wind field environment of QTT site for the improvement of telescope observation performance.In this paper,the basic theory of atmospheric boundary layer and numerical simulation involved in wind field research is expounded,and the processes of geographic model construction,grid division,boundary condition setting and parameter setting for numerical simulation of wind field are studied.In order to verify the accuracy of numerical simulation,this paper proposes to evaluate the error of numerical simulation based on the measured data of a single-point wind tower.The simulation results compare with the measured data,and the overall trend is consistent.The root mean square error(RMSE)of wind speed is less than 1m/s,and the minimum wind speed RMSE is 0.2m/s.Using the measured data,the monthly maximum wind speed,the hourly maximum wind speed and the wind rose diagram are analyzed;through the numerical simulation analysis,the wind speed profile of antenna position,the wind field streamline of site and the wind speed cloud map of 55 m height are studied.Based on the above analysis,the incoming wind at the antenna position is evaluated,and taking the wind rose diagram at 55 m height of the wind tower as a reference.It is predicted that the wind frequency in the antenna position is less than the wind tower in the north-south direction,and the wind frequency in the antenna position is greater than the wind tower in the east-west direction.For the wind resistance design of the antenna periphery,it should be mainly concentrated in the canyon mouth in the north direction of the antenna and the "L" shaped mountain in the southwest direction.If the wind resistance project is carried out first from the canyon mouth,its engineering volume is relatively small and it is easier to deal with.With the deepening pre-research of the QTT telescope,it is necessary to add a wind tower near the antenna to provide more accurate real-time wind field data for the telescope.Due to the traditional wind tower setup method cannot quantitatively evaluate the reliability of the setting point position,so a method based on numerical simulation to optimize the position of the wind tower is proposed in this paper.The implementation scheme sets the boundary conditions based on the specification parameters,while simplifying the wind field model.Its overall trend is consistent with the measured data,therefore the simulation accuracy could meet the requirement.4 wind tower positions are set in the range of 150 m from the antenna.According to simulation results the RMSE of wind speed between point P2 and the antenna position is the smallest.So,the measured data in P2 could better represent the wind field characteristics of the antenna area.