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KSME Journal

, Volume 10, Issue 2, pp 235–245 | Cite as

On the breakup mechanisms of air-assisted drops in a high speed air

  • Sang -Soon Hwang
Article
  • 174 Downloads

Abstract

An experimental study was performed to investigate break-up mechanisms of liquid drops injected into a transverse high velocity air jet. The range of conditions included the three drop breakup regimes previously referred to as bag, shear or boundary layer stripping, and ‘catastrophic’ breakup regimes. The results show that the break-up mechanism consists of a series of processes in which dynamic pressure effects deform the drop into a thin liquid sheet. The flattened drop subsequently breaks up into small droplets. At high relative velocity, in the ‘catastrophic’ breakup regime, drops are flattened and fragmented by relatively large wavelength waves whose wavelengths and growth rates are consistent with estimates from Rayleigh-Taylor instability theory. The minute drops that are also produced at this high relative velocity appear to originate from short wave length of Kelvin-Helmholtz waves growing on the larger liquid fragments.

Key words

Drop Breakup Drop Generator Instability Wave Breakup Regimes Weber Number 

Nomenclature

B1

Breakup time constant

Re

Reynolds number,Ud/v

T

Taylor parameter,ZW e2 0.5

t

Time

U

Air-liquid relative velocity

V

Liquid injection velocity, volume

We

Weber number,pU 2d/σ

Z

Ohnesorge number,μ L /(ρ L )1/2

ν

Wavelength, RT wavelength

μ

Viscosity

ω

Wave growth rate, RT wave growth rate

\(\bar \omega \)

Frequency

v

Kinematic viscosity

π

Fluid density

σ

Surface tension

KH wavelength of the most unstable surface waves

ω

KH growth rate of the most unstable surface waves

Subscripts

1

Liquid phase

2

Gas phase

bu

Breakup

d

Drop

g

Gas

j

Jet

L

Liquid

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References

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Copyright information

© The Korean Society of Mechanical Engineers (KSME) 1996

Authors and Affiliations

  • Sang -Soon Hwang
    • 1
  1. 1.Dept. of Mechanical EngineeringUniversity of InchonKorea

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