XI Session of the Russian Acoustical Society.
Moscow, November 19-23, 2001.
E.Yu.Rosina, O.N.Tistruga
THE SPECIAL FEATURES OF THE SOUND CAPILLARY EFFECT
IN THE DIELECTRIC LIQUIDS WITH HIGH VISCOSITY
Odessa State Academy of Refrigeration
Ukraine, 65026, Odessa, Dvoryanskaya str, b.1-3
Òål.: (048-2)209-146
Å-mail: elan@paco.net
Odessa National University
Ukraine, 65026, Odessa, Dvoryanskaya str, b.2-4
Òål: (048-2)206-784
The sound capillary effect has been investigated in the silica oil. It has been shown, that in liquids with
great viscosity if the real cavitation processes cannot be stimulated under the capillary cut, the stationary liquid
flow in capillary has been formed. The temperature distribution has been investigated in capillary cannel and
near the pulsing bubble, located under the capillary cut. The voltage difference in the capillary cannel has been
discovered. It has been connected with the translation motion of the microbubbles in the capillary cannel.
It is known, that the properties of the sound capillary effect (SCE) are distinguishing essentially
in linear precavitation and cavitation regimes. In linear precavitation regime the anomalous high
constant pressure affects the meniscus, located near the capillary cut, but liquid does not move
stationary along the capillary [1]. If the cavitation process is stimulated in liquid under the capillary
cannel, not only the high constant pressure arises, but powerful liquid flow forms also in capillary [24]. More often then not the investigation of the SCE has been connected with its cavitation regime,
and there is naturally, that the supposing reasons of the liquid flow in capillary has been connected
with the specific properties of the cavitation: the shock waves [3] and the cumulative microjets [4,5],
which accompany the collapse of cavities.
The results of our investigations [6,7] connect the linear precavitating and cavitating regimes by
the transition nonlinear precavitating regime. The special features of this transition regime are 1) the
periodical formation of the large gas bubble under the capillary cut; 2) liquid rising along the capillary
during the existence of this bubble, 3) the intensive gas dissolving in liquid. Based on experiments
we proposed the generalized point of view: according it, the every acoustical microinclusion, located
under the capillary cannel, is effected by the sound capillary pressure (SCP), and moves into the
cannel due to this pressure. Then the specific cavitation phenomena (the shock waves and high
velocity cumulative jets) are not the decisive factor in the production of the SCP and in the formation
of liquid flow. To assess the expediency of this assumption the experimental research of the SCE in
liquids with high viscosity will be provided. Using such liquids we will eliminate the true cavitation,
which is accompanied by the shock waves and high velocity cumulative jets.
As a tested liquid the silicone oil has been chosen, because its viscosity is 0,270 Pa·ñ, that is it
270 times more then viscosity of water. According the assessment for the hydrodynamic cavitation [8],
the cavity, arising in liquids with viscosity 1500 times more then water’s one, will be collapsed
never. The viscosity of the choosing liquid a few times less, then given above the threshold value.
But it is obviously, that the cumulative jets with the velocity 100-200 m/c will not be formed in such
liquid. The shock waves generated when the cavity with high radial velocity. In viscous liquid the
cavity will be slowly filled up instead of collapse, and the energy of the shock waves will be a few
order less, then in cavitating water, or in another usual liquid with low viscosity.
The using apparatus is shown schematically on Fig.1. The capillary 1 has been dipped into the
liquid, which fills up the vessel 2. The plane piezo- transduser 3 has been setup into the bottom of the
vessel, and the free end of the capillary has been arranged over it. By the generator 4 and the amplifier
5 the voltage with frequency 18.8 kHz has been carried to transducer. By the tap with cock 6 the
capillary has been connected with the manometer 7 and the compressor 8. To carry off liquid, arising
along the capillary, the cock 9 has been used. This cock opens the testing tube (it is not shown on
Fig.1) to measure the velocity of the liquid flow. The gaskets 10 and 10’ make the capillary system
air- and liquid-tight, when the measuring element 11 has been inserted into the capillary. This element
represent schematically both the thermocouple, which has been used for the thermal measurements,
113
XI Session of the Russian Acoustical Society.
Moscow, November 19-23, 2001.
and the copper prod, using for the electrical
investigation. One can move both elements along
the capillary axis and locate the sensor at
7
6
predetermined point. The thermovoltage and the
10'
electrical signal from the copper prod has been
12
10
registered with voltmeter 12 Before the test the
8
silica oil has been filtered, then degased by the
9
1
ultrasonic and cooled to room temperature.
To measure the sound capillary pressure
11
Ðsc,
(SCP) the statical pressure in capillary was risen
kPa
by compressor, when the voltage on the transducer
2
15
had been adjusted. In the range of voltage 0-120 V
Curve 1
the distorted meniscus moves to the capillary cut,
3
and SCP has been measured in the moment, when
10
the
bubble
have been broken off. The
4
5
dependence Ðsc(U) in this regime is the same as
5
received previously for the transformer oil [1] and
Curve 2
Fig.1.
Schematic of experimental apparatus
distilled water [7]. If voltage rises, the character of
processes changes: the large pulsating cavity
180 U, V
160
120
0
140
(bubble) is formed under the capillary cut, and liquid rises along the capillary. A like process
has
been observed for the distilled water, but the liquid Fig.2. The transducers voltage dependence
rising was nonstationary due to the periodical of the sound capillary pressure
intensive dissolving of the gas bubble. In case with dcap= 0,7 mm (curve 1), 2,7 mm (curve 2)
silicone oil the dissolving is not observed, the
forming cavity pulsates continuously, thus the liquid
flow in the capillary is steady. To control the piezoprod had been dipped into the silicone oil. It
registered the signal on the basic frequency of the
transducer, but
the cavitation noise near the
capillary was not registered. Thus, the steady flow
may be organized in capillary without true
cavitation under its cannel. The process near the
capillary cut and in its cannel was recorded by the
video. The produced
cavity
has essentially
irregular form: its bottom surface, presented to
transducer, pulsates, but holds its shape almost
spherical. The upper surface is drawn deep into the
capillary cannel, and the small bubbles breaks off from its top (Its size is about 0.1 mm). They do not
collapse and move in the capillary, thus in case of silicone oil the two-phase fluid flows in capillary.
In this regime the SCP is characterized by the maximal opposite pressure in capillary, which
stops the liquid rising; the dependence Ðsc (U) for two capillaries with different inner diameters is
shown in Fig.2. As one can see , increasing of the transducer voltage
leads to increasing of the
sound capillary pressure. This dependence has no peak and falling down part of curve, which
practically always exists in plots for the cavitating liquids with low viscosity.
It must be emphasized that the most essential feature of presented curves is the order of the
SCP, produced in cilicone oil. According the rezults, obtained in the experiments with distilled water,
by different authors [2-4,7] the order of the SCP is the same. Hence the cloud of cavities located
under the capillary cannel in distilled water does not produce additional pressure on the liquid in
capillary, if to compare it with the pressure, arising in silicone oil due to the pulsing of the large
bubble. This fact shows, that neither sock waves nor cumulative jets produce the measuring SCP. And
this experimental fact is correlate with the suggestion [6,7], that cloud of cavities, great pulsing bubble
and meniscus, located at the capillary cut, are the passive acoustical microinclusions, which are
affected by the sound capillary pressure.
114
XI Session of the Russian Acoustical Society.
Moscow, November 19-23, 2001.
The velocity of the two-phase silicone flow had been measured. Its value is 2-3 sm/c, thus it is
two order less then the velocity of the water flow ( it gets the 2-3 m/c); that fact is in the agreement
with the classical hydrodynamics.
Taking into consideration the high viscosity of the testing liquid, the measuring of the
temperature has been realized. The using thermocouple has the sensitivity α=35 ìV/degree and the
size of the sensor 0,2 mm. It has low specific heat, does not retard the flow in capillary, thus, the
temperature in capillary had been obtain in its true value.
The resulting distribution of temperature along the capillary axis in steady liquid flow is shown
in Fig.3. The vertical axis represent the differential value ∆Ò=T-T0, where Ò – is the temperature,
registered by thermocouple, and Ò0 – is the temperature in the vessel far from the pulsing bubble.
The temperature curve has two characteristic peaks.
The first peak rich the value 60-80îÑ and occurs
ÄÒ, îÑ
just bellow the surfase of the pulsing cavity. It is ÄÒ*max
probable that it is due to the viscous heating in the
45
circular microstreams, formed near the oscillating
surface. The second peak locates in capillary, rather
far from its open end. In our opinion, this peak is
connected with the translation motion microbubbles
30
ÄÒ**max
in the cannel.
So, the high temperature gradient have
established near the pulsing cavity under the
15
capillary cut in viscous liquid. One might expect
high gradient of viscosity in this region as a
sequence of the arising temperature gradient. It
h**
h*
should be noted, that silicone viscosity low less then
-3
0
5
10 h,10 ì
1,5 times [9]; but glycerin viscosity in this -5
temperature range decreases more then 10 times. .
The observation for the processes near the
capillary cut allows to state, that SCE gives the Fig.3. The distribution of temperature along
possibility to stable the phase-boundary surface near
the capillary axis (dcap= 0,7 mm)
the capillary cut in the ultrasonic field. It is well
known [10], that the polarization effect occures on
the phase-boundary surface, the double electrical layer forms in liquid, and it causes, so called,
electrical-kinetic phenomena. One of this phenomena is Dorn effect: if solid microparticles without
charges or gaseous bubbles move stationary in solution of electrolyte the voltage is registered in
liquid [11]. In our experiment the translation motion of bubbles in capillary cannel is also observed.
That is why the electrical measurments were provided. Before the ultrasonic wave was established in
vessel the low positive voltage ö î = +10ìV occures betveen prod 11 and earthed electrode Until the
transducer voltage still less then threshold value U* (120-130 Â) the ultrasonic action does not change
the potential of prod 11. If the transducer voltage goes over a threshold U* and pulsing bubble forms
under the capillary cut, the prod potential fall slowly, riches zero, reverses the sign and during 20-30
c gets new steady value öus. The electrical effect has been characterized with the difference prod
potential due to the ultrasonic action Äö=öus- ö î . The dependence Äö(U) is represented on Fig.4 for
two capillaries, which are distinguished with its inner diameters. As curves show, increasing of the
transducer voltage causes the nonlinear increasing of the steady negative potential Äö.
By manipulating the form and geometrical parameters of capillaries the next was founded.
The generation of the negative potential is due to the translation motion of the microbubbles in the
capillary cannel, its value connected with the direction and velocity of the bubble motion. The
potential generation may be interpreted as Dorn effect in the ultrasonic field.
Based on the presented experimental value Äö, according the suggested interpretation the
order of some value has been assessed. The voltage in the silicon surface double layer might be ~ 10-5
V. The surface density of charge in such double layer is not less, then 2,5·10-13 Kl/m2. In this case the
moving bubble carries the charge ~3·10-16 Kl. Thus, every microbubble removes from capillary cut
115
XI Session of the Russian Acoustical Society.
Moscow, November 19-23, 2001.
and large pulsing bubble the non compensated
charge, which is equivalent to charge of the ~103
Äö,
electrons. It must be note, that this values more
200 U,V
50
ìV
100 U* 150
0
less, then one can find in [10,11] for the same
parameters. But it should be considered that
-25
classical electrical-kinetic phenomena have been
Curve 2
researched for the solutions of electrolyte, because
free ions in liquids are necessary for the creation of
-50
the double layer. Not only high viscosity and its
slightly temperature dependence, but also high
-75
Curve 1
dielectric parameters characterize silicone oil [9].
This liquid has the highest specific resistance and
-100
practically unhygroscopic, it can endure voltage
Fig.4. The voltage dependence
about 104 V. The observation of the electricalof the sound capillary potential
kinetic phenomena, stimulated with the ultrasonic
Dcap= 0,7 mm (curve 1); 2,0 ì ì (curve 2).
action in silicone liquids, testifies that located
under the capillary precavitating process generates
the free charged particles even in such steady dielectric.
REFERENCES
1.
2.
Rosin Yu.P., Tihonova V.S. // Colloid. Journ.-1969.- N4.- P.568-572. (In Russian).
Rosin Yu.P., Tihonova V.S., Koctyuchek M.N. // Ukr.Phys.Journ.-1975.-V.20, N2.- P.214-220. (In
Russian).
3. Kitaigorodsky Yu.I., Drojalova V.N. // Ultrasonic application in metallurgy.-1977.-V.90.- P.12-16. (In
Russian).
4. Prohorenko P.P., Dejkunov N.IV., Konovalov G.E. Ultrasonic capillary effect.-Minsk: Nauka i technika,
1981.- 136 p. (In Russian).
5. Kuvshinov G.I., Prohorenko P.P Acoustical cavitation near the solid surface.- Minsk: Nauka i technika,
1990.- 112 p.
6. Rosin Yu.P. Rosina E.Yu. // Ukr.Phys.Journ.-1985.-V.30, N 2.-P.235-240. (In Russian).
7. Rosina E.Yu, Rosin Yu.P. // Ukr.Phys.Journ.- 1995.-V.40, N6.- P.553-558. (In Russian).
8. Knapp R.T., Daily J.W., Hammitt F.G. Cavitation.- McGraw-Hill B.C., New-York, 1970.- 687 p.
9. Sobolevskiy M.B., Muhovskaya O.Ya., Popeleva G.S. Properties and application of the silicone-organic
product. - Moscow: Chemistry, 1975.-1070 ñ. (In Russian).
10. Leb L. Statical elektricity.-M-L: Gov. Energetik pub.-1963.-407 p. (In Russian).
11. Duchin C.C., Deryagin B.V. Electrophoresis.- MOscow: Nauka, 1976.- 327 p. (In Russian).
116