국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	Some Flow Properties of Telescope Enclosures Estimated from Water Channel Tests-Application of The Flow Visualization Techniques-
저자	S. Shindo, K. Sakata, H. Ando, L. Barr, A. Miyashita
Keyword	Flow visualization; Circulating water channel; Telescope enclosures; Dome seeing; Telescope ventilation
URL	http://send.nal.go.jp/send/jpn/dlfile.php3/naltr1178t?doctype=7&filetype=20&path0=naltr1178t&path1=pdf&path2=naltr1178t.pdf
보고서번호	NAL TR-1178T
발행년도	1992.9
출처	NAL (National Aerospace Laboratory of Japan)
ABSTRACT	)arge 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(1:500 scale)were designed,i.e.,(1)a traditional shape having a circular cylinder base topped by a hemisphere(HS),(2)a straight-sided trapezoidal shape(NTT),and (3)a flat-roof cylinder with sidewall(ME),subsequently tested in the circulating water channel.Flushing of the enclosure was also closely observed via dye-injection.In all models,an external flow was observed that way″up-lifted″toward the top of the enclosure and separated from the original main flow stream direction at different levels depending on the model characteristics.It was found that the stagnation point of flow approaching the model′s front end should be above the outer edge of the turbulent boundary layer at the site.The time to flush out the enclosure was measured and found to vary with enclosure type,orientation of the viewing slit,and ventilation provisions.Sidewalls on either side of the telescope were found to be beneficial for flushing.In addition,flushing conditions were improved by incorporating vents situated somewhat orthogonal to the slit opening.The flat-roof cylinder type enclosure was determined to be superior from a ventilation standpoint.