This investigation presents computed base flow and stability data (axisymmetric disturbances) for impulsively started pipe entrance flows, and shows that at any given time, the displacement thickness (or any other flow variable) variation with axial distance is given by a varying portion which is accurately described by a steady, spatially developing flow, followed by a constant portion, described by the impulsively started parallel system. At the transition between these two systems is a small portion which is described by neither model. Arising from the inference that the latter region is sufficiently small to be neglected, variations in time and space of unstable regions in impulsively started pipe entrance flows were established, showing that (i) such flows are are unconditionally stable to infinitesimal axisymmetric disturbances for a Reynolds number of less than 23 350; (ii) for 38 770 > Re > 23 350, possible instability is confined to a maximum of 3.7% of the entire steady pipe entrance region; and (iii) for Re > 38 770, unstable regions may occur for finite time durations, over the entire length of the pipe.
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ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference
July 6–10, 2003
Honolulu, Hawaii, USA
Conference Sponsors:
- Fluids Engineering Division
ISBN:
0-7918-3697-5
PROCEEDINGS PAPER
Unstable Regions in Impulsively Started Pipe Entrance Flows Subjected to Infinitesimal Axisymmetric Disturbances Available to Purchase
E. A. Moss,
E. A. Moss
University of the Witwatersrand, Johannesburg, South Africa
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A. H. Abbot
A. H. Abbot
University of the Witwatersrand, Johannesburg, South Africa
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E. A. Moss
University of the Witwatersrand, Johannesburg, South Africa
A. H. Abbot
University of the Witwatersrand, Johannesburg, South Africa
Paper No:
FEDSM2003-45617, pp. 1079-1083; 5 pages
Published Online:
February 4, 2009
Citation
Moss, EA, & Abbot, AH. "Unstable Regions in Impulsively Started Pipe Entrance Flows Subjected to Infinitesimal Axisymmetric Disturbances." Proceedings of the ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. Volume 2: Symposia, Parts A, B, and C. Honolulu, Hawaii, USA. July 6–10, 2003. pp. 1079-1083. ASME. https://doi.org/10.1115/FEDSM2003-45617
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