Behavior of a horizontal air curtain subjected to a vertical pressure gradient

摘要

We present the details on an experiment to investigate the behavior of an air curtain that is subjected to a transversepressure gradient. The setup simulates the conditions that will be present in the Advanced Technology Solar Telescope(ATST), a 4-meter solar observatory that will be built on Haleakala, Hawaii. A test rig was built to replicate the region atwhich the optical path crosses a temperature and pressure boundary between the telescope mount region, which is at theambient temperature and pressure, and a warmer, pressurized lab space directly below. Use of an air curtain in place ofan optically-transmitting window at the interface would allow science observations at a wider range of scientificwavelengths. With the air curtain exhibiting transitional flow behavior across the boundary, and applied pressuregradients of up to 6.5 Pa, we found that the air curtain was able to hold a pressure gradient of 0.25 Pa. As the appliedpressure was increased, transient turbulent regions formed at the interface, and predictable flow behavior only occurredin the region closest to the air curtain blower. Computer modeling is used to validate the test data, identify laminarregions of the air curtain where minimal image distortion would occur, and explore the relationship between the appliedpressure, effective pressure difference, and air curtain profile.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.