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Modes in flow focusing and instability of coaxial liquid–gas jets

Published online by Cambridge University Press:  15 June 2009

TING SI ,
FANG LI ,
XIE-YUAN YIN  and
XIE-ZHEN YIN
TING SI
Affiliation:
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
FANG LI
Affiliation:
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
XIE-YUAN YIN
Affiliation:
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
XIE-ZHEN YIN*
Affiliation:
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China
*
†Email address for correspondence: xzyin@ustc.edu.cn
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Abstract

Six flow modes are distinguished in the flow-focusing experiments of a liquid jet forced by a high-speed air stream. The domains of the modes are identified on the parameter space of the liquid flow rate Ql and the gas pressure drop Δpg. The disturbance wavelength λ and breakup length L of the jet are also measured. A theoretical model considering axisymmetric disturbances is proposed, and a basic velocity profile of hyperbolic-tangent function is utilized. The linear temporal and spatio-temporal instability analyses are carried out using the Chebyshev collocation method. The effects of the flow parameters and the velocity profile on the flow instability are discussed. The temporal instability analysis demonstrates that the interfacial shear causes the instability of short waves and retards the instability of long waves. Moreover, the spatio-temporal instability analysis gives the transition boundary between the absolute and convective instability (AI/CI). The most unstable wavelength predicted by the temporal instability analysis and the AI/CI boundary predicted by the spatio-temporal instability analysis are in good agreement with the experimental results.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 629 , 25 June 2009 , pp. 1 - 23
Copyright
Copyright © Cambridge University Press 2009

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