Transition to asymmetry of transitional round fountains in a linearly stratified fluid

Gao, Wenfeng, Lin, Wenxian, Liu, Tao, Armfield, S.W., and Li, Ming (2017) Transition to asymmetry of transitional round fountains in a linearly stratified fluid. International Communications in Heat and Mass Transfer, 85. pp. 29-41.

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Abstract

In this study, a series of three-dimensional direct numerical simulations were carried out for transitional round fountains in a linearly-stratified fluid over the ranges of 100 <= Re <= 400, 1 <= Fr 8 and 0.0 <= s <= 0.3, where Fr, Re and s are the Froude, Reynolds, and dimensionless temperature stratification parameters, respectively, to examine, both qualitatively and quantitatively, the effect of these parameters on their transition to asymmetry and the asymmetric behavior. It is found that the transition to asymmetry are well represented and quantified by azimuthal velocity, with non-zero or noticeable azimuthal velocity indicating asymmetry. The results show that when Fr or Re are small, a fountain remains axisymmetric for all time; however, when Fr or Re are increased to be sufficiently large, the fountain will be axisymmetric initially, before becoming asymmetric and unsteady, ultimately reaching a fully developed quasi-steady stage when each quantity fluctuates over a constant, time average, value. The stratification is found to play a positive role to stabilize the flow and to reduce or even to eliminate the asymmetric behavior. The numerical results were also used to develop the scaling for the time for transition to asymmetry, which is found to be strongly dependent on Fr and s, while only weakly dependent on Re.

Item ID: 50362
Item Type: Article (Research - C1)
ISSN: 1879-0178
Keywords: transitional round fountain, asymmetric transition, stratification, direct numerical simulation
Funders: National Natural Science Foundation of China (NNSFC), Australian Research Council (ARC)
Projects and Grants: NNSFC 51469035 & 11662021, ARC #DP160102134
Date Deposited: 20 Sep 2017 08:16
FoR Codes: 09 ENGINEERING > 0915 Interdisciplinary Engineering > 091504 Fluidisation and Fluid Mechanics @ 80%
09 ENGINEERING > 0915 Interdisciplinary Engineering > 091508 Turbulent Flows @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970109 Expanding Knowledge in Engineering @ 100%
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