Chapter 8. Subsonic round and plane microjet in a
transverse acoustic field
Multimedia files Nos. 8.1 – 8.22
The results of researches presented in presentation are published in the following
main articles:
1.
V.V. Kozlov, G.R. Grek, Yu.A. Litvinenko, G.V. Kozlov, M.V. Litvinenko, Subsonic round and plane micro – jet in a
transverse acoustic field // Vestn. NSU. Seria: Physics. 2010. Vol. 5. Vip. 2, pp. 28-42, in Russian
2.
Yu.A. Litvinenko, G.R. Grek, V.V. Kozlov, G.V. Kozlov, Subsonic Round and Plane Macro - and Micro - Jets in a Transverse
Acoustic Field // Doklady Physics, 2011. Vol. 56, No. 1, pp. 26-31
Round microjet
Plane microjet
CONDITIONS OF THE EXPERIMENTS
Nozzle slot width
Microjet velocity
Reynolds number
Acoustic field frequency
Intensity of acoustic effect
200 ÷ 1600 mm
1 ÷ 10 m/s
20 ÷ 500
30 ÷ 1500 Hz
≤ 90 dB
Experimental Set – up for Round Microjet Generation
ROUND MACROJET, top – hat mean velocity profile
dnozzle = 5 mm, U0 = 1.5 m/s, Red = 500
Video file No. 8.1
Double click
here
ROUND JET, top – hat mean velocity profile
dnozzle = 1600 mm, Red = 500, F = 40 Hz
Video file No. 8.2
Without and with acoustics
Double click
here
Smoke visualization of the round microjet evolution under action of
transverse acoustic field:
1 – jet with ring vortices, 2 – micro – jet with parabolic mean velocity profile at
the nozzle exit, 3 - micro – jet with top - hat mean velocity profile at the nozzle
exit.
ROUND MICROJET,
dnozzle = 1600 mm
F= 80Гц
ROUND MICROJET
U = 1.5 m/s, Red = 160, dnozzle = 1600 mm, F = 40 Hz
Video file No. 8.3
Parabolic mean velocity profile
Double click
here
Double click
here
Video file No. 8.4
Top – hat mean velocity profile
Double click
here
ROUND MICROJET
Top – hat mean velocity profile
dnozzle = 500 mm, F = 0 ÷ 1500 Hz
Video file No. 8.5
Double click
here
ROUND MICROJET
Top – hat mean velocity profile
dnozzle = 200 mm, F = 200 Hz
Video file No. 8.6
Double click
here
ROUND MICROJET
Parabolic mean velocity profile
dnozzle = 400 mm, F = 200 Hz
Video file No. 8.7
Smoke visualization patterns of the round microjet under
action of transverse acoustic field (F = 200 Hz) at different
nozzle diameter
Experimental Set – up scheme for Plane Micro – Jet
Generation
PLANE MACROJET
under action of transverse acoustic field
U = 4 m/s, l = 35 mm, hnozzle = 2.5 mm, F = 30 Hz
Double click
here
Video file No. 8.8
PLANE MICROJET
(ratio of the nozzle sides, l/h = 12 )
U = 2 m/s, l = 2360 mm, hnozzle = 200 mm, Reh = 160
U
PLANE MICROJET with and without action of transverse
acoustic field
U = 2 m/s, l = 2360 mm, hnozzle = 200 mm, F = 0 ÷ 60 Hz
(view of the nozzle narrow side)
Video file No. 8.9
Double click
here
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, l = 2360 mm, h = 200 mm, F = 800 ÷ 1300 Hz
(view of the nozzle narrow side)
Video file No. 8.10
Double click
here
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, l = 2360 mm, hnozzle = 200 mm, F = 1300 Hz
Video file No. 8.11
Double click
here
View of the nozzle length side,
microjet does not disperse
Video file No. 8.12
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here
View of the nozzle narrow side,
microjet disperse
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, lnozzle = 2360 mm, hnozzle = 200 mm, F = 1300 Hz
PLANE MICROJET, natural oscillations
U = 2 m/s, lnozzle = 36000 mm, hnozzle = 200 mm
Double click
here
Video file No. 8.13
SCHEME OF THE PLANE MICROJET BIFURCATION AND FOLDING
IN A TRANSVERSE ACOUSTIC FIELD
лазер
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, lnozzle = 36000 mm, hnozzle = 500 mm, F = 100 Hz, z = 0 mm
Double click
here
Video file No. 8.14
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, lnozzle = 36000 mm, hnozzle = 500 mm, F = 100 Hz,
z = ± 18 mm
Video file No. 8.15
Double click
here
PLANE MICROJET FOLDING
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, lnozzle = 36000 mm, hnozzle = 500 mm, F = 100 Hz,
z = 0 mm
Double click
here
Video file No. 8.16
PLANE MICROJET under action of transverse acoustic field
U = 2 m/s, lnozzle = 36000 mm, hnozzle = 500 mm, F = 100 Hz, z = 0 mm
Double click
here
Video file No. 8.17
SCHEME OF THE PLANE MACRO – AND MICROJET SINUSOIDAL
INSTABILITY
PIV – MEASUREMENTS OF THE PLANE MICROJET
(vorticity field, wz )
Plane microjet, natural oscillations,
d = 2500 mm, l = 36000 mm, U= 2 m/s
Plane microjet, acoustic field,
F= 30 Hz, d = 2500 mm,
l = 36000 mm, U= 3 m/s
PLANE MICROJET, l/h = 13.3, h = 2.5 mm, F= 80 Hz (PIV)
Vector field (UV- velocity components) and vorticity wz
u y
u x
wz  (

)
x
y
m/s
1.956
1.825
1.695
1.565
1.434
wz
1.304
1.174
1.043
0.9128
0.7825
0.6521
0.5217
0.3914
0.261
0.1306
VORTICITY FIELD, wz
PLANE MICROJET, l/h = 13.3, h = 2.5 mm, F= 80 Hz, U = 2 m/s
Double click
here
Video file No. 8.18
VORTICITY FIELD, wz
PLANE MICROJET, l/h = 13.3, h = 2.5 mm, F= 120 Hz,
U = 2 m/s
Double click
here
Video file No. 8.19
VORTICITY FIELD, wz
PLANE MICROJET, l/h = 13.3, h = 2.5 mm, F= 140 Hz,
U = 2 m/s
Double click
here
Video file No. 8.20
PLANE MICROJET
Comparison of the acoustic field and nozzle vibrations effect on
the plane microjet, l = 40 mm, h = 300 mm, U = 1 m/s
Acoustic field, F = 32 Hz
Video file No. 8.21
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here
Nozzle vibrations in l-plane, F = 32 Hz
Video file No. 8.22
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here
KEY POINTS:

Kelvin - Helmholtz instability mechanism of a round jet with a top – hat mean velocity
profile at the nozzle exit is kept till of a macrojet diameter about 5 mm.

Mechanism of a microjet evolution both with a top – hat and parabolic mean velocity
profile at the nozzle exit cardinally varies.

The new phenomenon connected to transformation of a round microjet in a plane
microjet under influence of a transverse acoustic field is revealed.

Round microjet downstream evolution is defined by the mechanism of the plane jet
sinusoidal vortex instability.

The phenomenon of a microjet bifurcation on two jets developing independently from
each other is revealed.

Two new microjets are developed under the certain angle to each other and subjected to
high-frequency secondary instability.

Sinusoidal instability of a plane jet is kept for macro - and microjets both with acoustic
and without acoustic effect.
KEY POINTS:
 Acoustic influence on a pseudo plane microjet (l/h = 10) results in the mechanism of its
development similar to the mechanism of development of a round microjet in a transverse
acoustic field.
 Pseudo plane microjet at the presence of an acoustic field shows presence in it of the vortex
structures and dependence of a bifurcation angle of a jet on frequency of acoustic effect.
 New phenomenon, so-called microjet (l/h = 70, 180) folding at its edges in direction of a
variable flow velocity vector created by a transverse acoustic field is demonstrated.
 Plane microjet folding process results in extinction of the jet downstream evolution and
prevent of its further turbulisation.
 Distinction in kind of the acoustic field influence both on the round and plane microjets
instability is found. It is shown, that sinusoidal instability of a round microjet depends
on direction of a velocity vector of an acoustic field, and instability of a plane microjet does not depend.
 New phenomena which have been found out during studies of development both round and
plane microjets are caused, probably, by a commensurability of energy of a transverse
acoustic field with energy of the microjets.