Problem № 2 “Aerosol”

1.

Problem № 2
“Aerosol”
When water flows through a small aperture,
an aerosol may be formed. Investigate the
parameters that determine whether an
aerosol is formed rather than a jet for
example. What are the properties of the
aerosol?
Team Russia
Reporter: Nika Gribova

2.

Review
Introduction to the production and
properties of the aerosol
Aerosol properties.
Assemble an experimental
setup
Studying of the break-up
mechanisms of the jet into drops.
The role of air.
Analysis of the work and
conclusions.
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3.

Basic concepts
Aerosol is a dispersed system which consists of small particles suspended in a
gaseous medium. Size of particles in aerosols vary from a few millimeters to ten
to the power of minus 7 m.
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Experimental Setup
Theory Model
Optimization
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4. The method of producing aerosol

Dispersing aerosols
Condensation aerosol
Disintegration of solid and
liquid substances
Cooling and the formation of
supersaturated vapor, some
chemical reactions
The type of aerosol and the way of it`s producing uniquely defined by the
condition of the problem - spraying a jet of water as it passes through a
small aperture.(dispersing aerosol)

5. Scheme of jet disintegration

Vapor bubbles and Waves on the
turbulence
free surface
of the fluid
The gaseous
bubbles
Droplets
Reasons:
Instabilities and
perturbations, which arise in
the jet itself:
• Cavitation
• Turbulent flows
Jet disintegration due to
interaction with the air
several sticky
droplets
Fath, A., Fettes, C., and Leipetz, A. 1998. Investigation of the Diesel Break - up Close to the Nozzle at Different Injection Conditions, The Fourth
International Symposium COMODIA 98, p.p. 429 - 434, Kyoto, Japan

6. Aerodynamic regimes

Experimental setup
шланг
tube
насос
pump
штатив
tripod
nozzle

7. REVIEW OF INVESTIGATION

DETERMINATION OF DROPLET SIZE
• The depth of field
15 – 20 сm
3 – 5 mm

8.

6,14 10 4 м
3,13 10 3 м
6 10 4 м
2,86 10 3 м
3
1,84 10 м
3,41 10 5 м
2,3 10 5 м
6,91 10 4 м
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1,15 10 4 м
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9.

Jet flow mode
Re
U-velocity of the jet
D-diameter of aperture
-dynamic viscosity
-density of the jet
Ud
Viscous friction force and dynamic
pressure force of liquid jet
The Reynolds number is a criterion for the hydrodynamic similarity of a viscous fluid flow, included the ratio of
inertial forces to viscous friction forces.

10.

INVESTIGATING JET`S BREAK-UP PROCESS
Laminar flow
Re < 2100
Semi-turbulent flow
2100<Re < 2300
Turbulent flow
Re >2300
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Experimental Setup
Theory Model
Optimization
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11. Jet flow mode

Rayleigh-Plateau instabilities
L
• Laminar flow
• The characteristic time of jet disintegration of the
initial radius Rₒ is equal to
ρ