Self-Preserving Properties of Unsteady Round Buoyant Turbulent Plumes and Thermals in Still Fluids  

Oleh:

Diez, F. J. ; Sangras, R. ; Faeth, G. M. ; Kwon, O. C.

Jenis: Article from Bulletin/Magazine
Dalam koleksi: Journal of Heat Transfer vol. 125 no. 5 (Oct. 2003), page 821-830.
Topik: turbulent flows; self - preserving; properties; unsteady round; bouyant turbulent; plumes and thermals

Ketersediaan

Perpustakaan Pusat (Semanggi) Nomor Panggil: JJ90.7 Non-tandon: 1 (dapat dipinjam: 0) Tandon: tidak ada

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Isi artikel

The self - preserving properties of round buoyant turbulent starting plumes and starting jets in unstratified environments. The experiments involved dye - containing salt water sources injected vertically downward into still fresh water within a windowed tank. Time - resolved images of the flows were obtained using a CCD camera. Experimental conditions were as follows : source diameters of 3.2 and 6.4 mm, source / ambient density ratios of 1.070 and 1.150, source Reynolds numbers of 4,000 – 11,000, source Froude numbers of 10 – 82, volume of source fluid for thermals comprising cylinders having the same cross - sectional areas as the source exit and lengths of 50 – 382 source diameters, and streamwise flow penetration lengths up to 110 source diameters and 5.05 Morton length scales from the source. Near-source flow properties varied significantly with source properties but the flows generally became turbulent and then became self-preserving within 5 and 20 – 30 source diameters from the source, respectively. Within the self - preserving region, both normalized streamwise penetration distances and normalized maximum radial penetration distances as functions of time were in agreement with the scaling relationships for the behaviour of self - preserving round buoyant turbulent flows to the following powers : time to the 3/4 power for starting plumes and to the 1/2 power for thermals. Finally, the virtual origins of thermals were independent of source fluid volume for the present test conditions.

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