Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992stin...9413452s&link_type=abstract
Unknown
Astronomy and Astrophysics
Astronomy
Air Cooling, Domes (Structural Forms), Enclosures, Flow Distribution, Flow Visualization, Telescopes, Ventilation, Water Tunnel Tests, Cylindrical Shells, Flushing, Hemispherical Shells, Hydraulic Test Tunnels, Image Processing, Method Of Moments, Temperature Profiles, Trapezoids
Scientific paper
Studies on the seeing conditions inside telescope domes indicate that substantial air ventilation is necessary to prevent image degradation due to thermal nonuniformity of the air within the dome, especially for a dome as large as the Japan National Large Telescope (JNLT). In traditional telescope enclosures, in which a cylinder is topped by a hemispherical dome, the air flow quality is influenced by factors such as temperature fluctuations and the distribution of dust contamination which affect the seeing conditions. To determine the best telescope shape from a perspective of achieving desirable air ventilation conditions, the National Aerospace Laboratory (NAL) and National Astronomical Observatory (NAO) jointly studied dome shapes. Flow visualization techniques were applied to the tests using a circulating water channel developed by the NAL Aeroengine Division in order to evaluate flow properties inside and outside models of a telescope enclosure. The hydrogen bubble method and dye injection technique with image processing were primarily utilized. Three types of enclosure models (one to 500 scale) were designed: (1) a traditional shape having a circular cylinder base topped by a hemisphere (HS); (2) a straight-sided trapezoidal shape (New Technology Telescope, NTT); and (3) a flat-roof cylinder with sidewall (Modified Enclosure, ME); subsequently tested in the circulating water channel. Flushing of the enclosure was also closely observed via dye-injection.
Andou Hiroyasu
Barr L.
Miyashita Akihiko
Sakata Kimio
Shindou Shigemi
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