A NEW METHOD OF FLOW VISUALIZATION FOR LOW DENSITY WIND TUNNELS
Technical Report
·
OSTI ID:4331883
The absorption by O/sub 2/ of radiation in the wavelength region 1400 to 1500A is utilized and is referred to as the O/sub 2/ absorption method. It was developed for use in the lowdensity supersonic continuous flow wind tunnels at Berkeley because the conventional methods (shadowgraph, schlieren, and interferometer) were predicted to have inadequate sensitivity at the unusually low densities in the test section. A Xe discharge is used for the source of radiation, its 1470A resonance line being isolated by a CaF/sub 2/ vacuum monochromator. A 26 mm dianneter beam of parallel radiation is passed through the test section where it is absorbed more or less depending on the O/sub 2/ density along the radiation path. The center of the test section is then focused by a CaF/sub 2/ vacuum camera on an ultraviolet sensitive photographic plate. Pictures of shock waves from cylinders 1/8 and 1/4 in. diameter and from a 60 deg , 3/8 in. wedge were obtained with exposure times of about 4 min. Further development of a stronger source is expected to reduce the exposure time appreciably. This O/sub 2/ absorption method is shown to be suitable for general wind tunnel work where the absolute pressures are below about 1 mm Hg. A simplified analysis of five flow visualization methods as applied to a two- dimensional circular shock wave is presented, and the minimum detectable density difference is estimated for each. (auth)
- Research Organization:
- California. Univ., Berkeley. Inst. of Engineering Research
- NSA Number:
- NSA-12-000360
- OSTI ID:
- 4331883
- Report Number(s):
- HE-150-119
- Country of Publication:
- United States
- Language:
- English
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