Author:
LASHERAS J. C.,VILLERMAUX E.,HOPFINGER E. J.
Abstract
The near- and far-field break-up and atomization of a water jet
by a high-speed
annular air jet are examined by means of high-speed flow visualizations
and phase
Doppler particle sizing techniques. Visualization of the jet's near
field and
measurements of the frequencies associated with the gas–liquid interfacial
instabilities
are used to study the underlying physical mechanisms involved in the primary
break-up
of the water jet. This process is shown to consist of the stripping of
water sheets,
or ligaments, which subsequently break into smaller lumps or drops. An
entrainment
model of the near-field stripping of the liquid is proposed, and shown
to describe the
measured liquid shedding frequencies. This simplified model explains qualitatively
the
dependence of the shedding frequency on the air/water momentum ratio
in both
initially laminar and turbulent water jets. The role of the secondary liquid
break-up in
the far-field atomization of the water jet is also investigated, and an
attempt is made
to apply the classical concepts of local isotropy to explain qualitatively
the
measurement of the far-field droplet size distribution and its dependence
on the water
to air mass and momentum ratios. Models accounting for the effect of the
local
turbulent dissipation rate in the gas on both the break-up and coalescence
of the
droplets are developed and compared with the measurements of the variation
of the
droplet size along the jet's centreline. The total flux of kinetic
energy supplied by the
gas per unit total mass of the spray jet was found to be the primary parameter
determining the secondary break-up and coalescence of the droplets in the
far field.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
317 articles.
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