A Study of Baffle Turbulence in Open Truss Telescope Based on CFD Software

Primary baffle would influence the airflow above the primary mirror, which is not conducive to heat exchange between the mirror's surface and the ambient air. The 50cm Telescope at Xinglong Observatory is influenced by two kinds of stray light suppression devices-baffle and vanes. In this paper, an analysis of airflow and temperature around the primary mirror of the 50cm Telescope has been carried out with CFD software. Mirror seeing has also been calculated with CFD data. Analysis results indicate that,the primary baffle will cause nonuniform temperature distribution, large area of turbulence and asymmetry vortex. In the case of independent vanes, mirror seeing decreases by 74%. These results show that the primary baffle has major disadvantages in respect of mirror cooling and air circulation. With the help of airflow and stray light analysis, plans for stray light control can be chosen more reasonably. The CFD analysis method could be helpful to telescope design and transformation.