NUMERICAL SIMULATIONS OF AIR-FLOW IN TELESCOPE ENCLOSURES

Contemporary design of large telescopes requires optimization of the t elescope environment in order to fully realize the capabilities of adv anced mirror technology, telescope control, and instrumentation. Teles cope enclosure design is a critical element in providing this optimize d environment. Enclosures must protect the telescope while minimizing the local degradation of image quality, and the large cost of such str uctures requires that a successful design be in place before construct ion begins. In order to test various enclosure designs, three-dimensio nal nonlinear hydrodynamic calculations have been carried out to deter mine the flow of air within and around proposed enclosure configuratio ns. Such calculations can test the effectiveness of dome venting, eval uate the dynamic pressures that cause possible deformation of primary mirror surfaces and structural windshake, and isolate sources of turbu lent flow that may cause image degradation. Results are presented from a series of calculations that investigated characteristic flows in th e Gemini 8-meter enclosure and around its associated primary mirror ce ll. In general the enclosure design is found to meet its overall desig n goals. Good dome venting is achieved under a variety of conditions, yet the telescope structure is kept in a low wind environment. (C) 199 6 American Astronomical Society.