Onset of entrainment in transitional round fountains

Lin, Wenxian, and Armfield, S.W. (2008) Onset of entrainment in transitional round fountains. International Journal of Heat and Mass Transfer, 51. pp. 5226-5237.

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Abstract

It is of fundamental interest to understand the behavior of transitional fountains with intermediate Froude and Reynolds numbers, together with the associated entrainment and turbulence. In this work, the transient behavior of axisymmetric fountains with 1 6 Fr 6 8 and 200 6 Re 6 800 is studied by direct numerical simulation. It is found that at Re 6 200, there is little entrainment present at the upflow–downflow interface and at the downflow–ambient interface, even for a value of Fr as high as 8; however, at Re > 200, entrainment is present at these interfaces and the extent increases with Re, which clearly demonstrates that entrainment is strongly dependent on Re whereas the contribution from the Fr effect is relatively much smaller. The DNS results also show that zm, which is the maximum fountain penetration height, fluctuates, even when the flow reaches full development, due to the entrainment at the upflow–downflow and the downflow–ambient interfaces, and the averaged zm scales with Fr32Re14 for 1 < Fr 6 8 and 100 6 Re 6 800.

Item ID: 4813
Item Type: Article (Refereed Research - C1)
Keywords: transitional fountain, entrainment, direct numerical simulation, turbulent flow
ISSN: 1879-2189
Funders: Australian Research Council, National Natural Science Foundation of China
Date Deposited: 30 Jul 2009 04:58
FoR Codes: 09 ENGINEERING > 0915 Interdisciplinary Engineering > 091504 Fluidisation and Fluid Mechanics @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970109 Expanding Knowledge in Engineering @ 60%
97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 40%
Citation Count from Web of Science Web of Science 8
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