OPTICAL MEASUREMENT OF RADIAL DENSITY DISTRIBUTIONS IN A HIGH-SPEED CONFINED AIR VORTEX.
Abstract
An optical method based on light-deflection mapping was developed and used to determine the radial variation of fluid density in a high-pressure-ratio (20:1), high-speed, confined air vortex of about 3 inches diameter. An intense, parallel, thin light beam was transmitted laterally through the vortex at various off-axis positions, and the small light deflections caused by the density field of the vortex were measured. From the variation of the deflection angle over the radius, the radial density profile was numerically calculated by assuming rotational symmetry and solving the resulting integral equation. The density profile was determined in two cross-sections of the vortex, at various operating conditions of the chamber. The results show that the core region in which the fluid rotates like a solid body has a very uniform diameter corresponding to about half of the exhaust port diameter. The presence of axial density differences, which are related to the meridional flow movements, is clearly shown. In a further experiment, the disturbance of the density profile caused by a static-pressure probe was determined for various radial penetrations of the probe. Besides acoustic resonance a considerable density fluctuation was observed, especially at radii smaller than that of the exhaust opening. This finding indicates the existence of periodic fluctuations in the rotational speed of the vortex. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1967
- Accession Number
- AD0666460
Entities
People
- George Gyarmathy
Organizations
- Air Force Research Laboratory