Onset of asymmetry and three-dimensionality in transitional round fountains in a linearly stratified fluid

Gao, Wenfeng, Lin, Wenxian, Liu, Tao, and Armfield, Steven (2012) Onset of asymmetry and three-dimensionality in transitional round fountains in a linearly stratified fluid. In: Proceedings of the 18th Australasian Fluid Mechanics Conference, pp. 1-4. From: 18th Australasian Fluid Mechanics Conference, 3-7 December 2012, Launceston, Tasmania, Australia.

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Abstract

Fountains injected into stratified fluids are widely found in nature and engineering settings. The onset of asymmetry, three dimensionality and entrainment which occurs in transitional fountains is the key to shed light on the turbulence generation mechanism in fountains. It is also apparent that the stratification of the ambient fluid has significant effects on the onset of asymmetry, three-dimensionality and entrainment in fountains and a study on such effects will provide further insight into the interaction between stratification and turbulence generation mechanism in fountains. In this study, a series of direct numerical simulations were carried out for transitional round fountains in the ranges of 1<=Fr<=8, 100<=Re<=500 both in a homogeneous fluid and in a linearly stratified fluid with a constant dimensionless stratification s = 0.03, aiming at providing insights into the onset of asymmetry and three-dimensionality in transitional round fountains in a linearly stratified fluid when compared to that in a homogeneous fluid. The results show that a critical Re exists between 100 and 200 for Fr = 2 fountains which divides the fountains as either axisymmetric or asymmetric and three-dimensional; similarly a critical Fr exists between 1 and 2 for fountains at Re = 200 which divides the fountains as either axisymmetric or asymmetric and three-dimensional; when Re>=200, the Fr = 2 fountains maintain axisymmetry only in the developing stage and become asymmetric and threedimensional at fully developed, steady state, and the stratified case has in general stronger extents of asymmetry and threedimensionality than the homogeneous case; when Fr>=2, the fountains at Re = 200 maintain axisymmetry only in the developing stage and become asymmetric and three-dimensional at fully developed, steady state, and the stratified case has much stronger extents of asymmetry and three-dimensionality than the homogeneous case; The occurrence of asymmetry and three-dimensionality becomes much earlier when Re or Fr increases.

Item ID: 24258
Item Type: Conference Item (Refereed Research Paper - E1)
Keywords: transitional fountain; asymmetry; direct numerical simulation; critical Reynolds number; critical Froude number; entrainment
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ISBN: 978-0-646-58373-0
Funders: National Natural Science Foundation of China, Yunnan Natural Science Foundation, China, Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China, Australian Research Council
Date Deposited: 04 Jan 2013 05:21
FoR Codes: 09 ENGINEERING > 0915 Interdisciplinary Engineering > 091504 Fluidisation and Fluid Mechanics @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970109 Expanding Knowledge in Engineering @ 100%
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