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Buoyant Turbulent Jets and Flames. Part 3. Round Turbulent Nonbuoyant Starting Jets and Puffs and Buoyant Starting Plumes and Thermals. Annual Report.


pdf icon Buoyant Turbulent Jets and Flames. Part 3. Round Turbulent Nonbuoyant Starting Jets and Puffs and Buoyant Starting Plumes and Thermals. Annual Report. (1848 K)
Sangras, R.; Dai, Z.; Faeth, G. M.

GDL/GMF-99-03; 37 p. October 1999.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Keywords:

turbulent jets; turbulent flames; buoyant plumes; buoyant flow; experiments; salt water

Abstract:

A theoretical and experimental study of the temporal development of round turbulent nonbuoyant starting jets and puffs and buoyant starting plumes and thermals is described, limited to sources in still and unstratified environments. The experiments involved dye-containing salt or fresh water sources injected vertically downward into fresh water within a large windowed tank with injector passage length/diameter ratios of 50. Time-resolved video images of the flows were obtained using a CCD camera. Initial jet exit conditions were as follows: diameters of 3.2-12.7 mm, Reynolds numbers of 1450-11700 and jet/ambient density ratios of 1.00-l.12. Near-source behavior varied significantly with source properties but the flows generally became turbulent near the jet exit with self-preserving behavior generally observed at distances greater than 20-30 source diameters from the source. Within the self-preserving region, both the normalized streamwise penetration distance and the normalized maximum flow radius varied as function of time to the following powers: l/2 (starting nonbuoyant jet), l/4 (nonbuoyant puff), 3/4 (starting buoyant plume), and l/2 (buoyant thermal).