The study investigates how an acoustic field influences evaporation and internal circulation of twin drops when their in-between horizontal spacing varies. The acoustic source is a simple sine wave (i) with and (ii) without white noise at various frequencies. The circulation and outer flow are visualized. Maximum evaporation rate and circulation are found for the lowest frequency and highest spacing. The rate rises with the spacing for a given frequency up to a critical distance. The evaporation becomes almost identical beyond the critical spacing. A correlation among the spacing, evaporation rate, and outer flow velocity is demonstrated. The rate becomes lowest for a given frequency at the least spacing since the vapors accumulated in the surrounding are not swept out by the acoustic-induced flow. The visualization shows a horizontal outer flow, which becomes vertical with the rise in spacing because the acoustic wave can sweep the vapor out. The horizontal flow for the least spacing transforms itself to vertical when the wave amplitude is raised. The evaporation thus rises because the wave now sweeps the vapors out. We show that the perception that any acoustic wave enhances the evaporation of multiple nearby drops is incorrect. The evaporation and circulation decline faster with the rise in frequency since the surrounding flow becomes weak. Thus, we show how the spacing influences the evaporation when acoustic is incident and how the evaporation can be raised by sweeping the accumulated vapor out using higher amplitude acoustics for the closer drops.

1.
Abramzon
,
B.
and
Sirignano
,
W. A.
, “
Droplet vaporization model for spray combustion calculations
,”
Int. J. Heat Mass Transfer
32
,
1605
1618
(
1989
).
2.
Bansch
,
E.
and
Gotz
,
M.
, “
Numerical study of droplet evaporation in an acoustic levitator
,”
Phys. Fluids
30
,
037103
(
2018
).
3.
Bennacer
,
R.
and
Sefiane
,
K.
, “
Vortices, dissipation and flow transition in volatile binary drops
,”
J. Fluid Mech.
749
,
649
665
(
2014
).
4.
Brenn
,
G.
,
Deviprasath
,
L. J.
,
Durst
,
F.
, and
Fink
,
C.
, “
Evaporation of acoustically levitated multi-component liquid droplets
,”
Int. J. Heat Mass Transfer
50
,
5073
5086
(
2007
).
5.
Bryan
,
W. H.
, “
The essentials of continuous evaporation
,”
Am. Inst. Chem. Eng.
114
,
24
28
(
2018
).
6.
Chakraborty
,
S.
,
Rosen
,
M. A.
, and
McDonald
,
B. D.
, “
Analysis and feasibility of an evaporative cooling system with diffusion-based sessile droplet evaporation for cooling microprocessors
,”
Appl. Therm. Eng.
125
,
104
110
(
2017
).
7.
Christy
,
J. R. E.
,
Hamamoto
,
Y.
, and
Sefiane
,
K.
, “
Flow transition within an evaporating binary mixture sessile drop
,”
Phys. Rev. Lett.
106
,
205701
(
2011
).
8.
Danilov
,
S. D.
and
Mironov
,
M. A.
, “
Breakup of a droplet in a high-intensity sound field
,”
J. Acoust. Soc. Am.
92
,
2747
2755
(
1992
).
9.
Deegan
,
R. D.
,
Bakajin
,
O.
,
Dupont
,
T. F.
,
Huber
,
G.
,
Nagel
,
S. R.
, and
Witten
,
T. A.
, “
Capillary flow as the cause of ring stains from dried liquid drops
,”
Nature
389
,
827
829
(
1997
).
10.
Fang
,
X.
,
Li
,
B.
,
Petersen
,
E.
,
Ji
,
Y.
,
Sokolov
,
J. C.
, and
Rafailovich
,
M. H.
, “
Factors controlling the drop evaporation constant
,”
J. Phys. Chem. B
109
,
20554
20557
(
2005
).
11.
Fang
,
X.
,
Pimentel
,
M.
,
Sokolov
,
J.
, and
Rafailovich
,
M.
, “
Dewetting of the three-phase contact line on solids
,”
Langmuir
26
,
7682
7685
(
2010
).
12.
Girard
,
F.
,
Antoni
,
M.
,
Faure
,
S.
, and
Steinchen
,
A.
, “
Influence of heating temperature and relative humidity in the evaporation of pinned droplets
,”
Colloids Surf., A
323
,
36
49
(
2008
).
13.
Hasegawa
,
K.
,
Watanabe
,
A.
,
Kaneko
,
A.
, and
Abe
,
Y.
, “
Internal flow during mixing induced in acoustically levitated droplets by mode oscillations
,”
Phys. Fluids
31
,
112101
(
2019
).
14.
He
,
M.
and
Qiu
,
H.
, “
Internal flow patterns of an evaporating multicomponent droplet on a flat surface
,”
Int. J. Therm. Sci.
100
,
10
19
(
2016
).
15.
Hegseth
,
J. J.
,
Rashidnia
,
N.
, and
Chai
,
A.
, “
Natural convection in droplet evaporation
,”
Phys. Rev. E
54
,
1640
1644
(
1996
).
16.
Hu
,
H.
and
Ronald
,
G. L.
, “
Marangoni effect reverses coffee-ring depositions
,”
J. Phys. Chem. B
110
,
7090
7094
(
2006
).
17.
Joyce
,
M. J.
,
Todaro
,
P.
,
Penfold
,
R.
,
Port
,
S. N.
,
May
,
J. A. W.
,
Barnes
,
C.
, and
Peyton
,
A. J.
, “
Evaporation of sessile drops: Application of the quartz crystal microbalance
,”
Langmuir
16
,
4024
4033
(
2000
).
18.
Kitano
,
T.
,
Nishio
,
J.
,
Kurose
,
R.
, and
Komori
,
S.
, “
Effects of ambient pressure, gas temperature and combustion reaction on droplet evaporation
,”
Combust. Flame
161
,
551
564
(
2014
).
19.
Kobayashi
,
K.
,
Goda
,
A.
,
Hasegawa
,
K.
, and
Abe
,
Y.
, “
Flow structure and evaporation behavior of an acoustically levitated droplet
,”
Phys. Fluids
30
,
082105
(
2018
).
20.
Kumar
,
A.
and
Mandal
,
D. K.
, “
Oscillatory circulation inside evaporating methanol–water drops
,”
Int. J. Multiphase Flow
102
,
130
137
(
2018
).
21.
Kumar
,
A.
,
Prasad
,
S.
,
Pal
,
P.
,
Narayanan
,
S.
, and
Mandal
,
D. K.
, “
Circulation inside a methanol–water drop evaporating in a heated atmosphere
,”
Colloids Interface Sci. Commun.
24
,
82
86
(
2018
).
22.
Li
,
C.
,
Shi
,
Z.
,
Xiao
,
H.
, and
Ye
,
X.
, “
Effect of surfactant and evaporation on the thin liquid film spreading in the presence of surface acoustic waves
,”
Phys. Fluids
32
,
062106
(
2020
).
23.
Mahravan
,
E.
,
Naderan
,
H.
, and
Damangir
,
E.
, “
Analysis of free surface oscillations of a droplet due to ultrasonic wave impingement
,”
Phys. Fluids
32
,
092111
(
2020
).
24.
Mandal
,
D. K.
and
Bakshi
,
S.
, “
Internal circulation in a single droplet evaporating in a closed chamber
,”
Int. J. Multiphase Flow
42
,
42
51
(
2012a
).
25.
Mandal
,
D. K.
and
Bakshi
,
S.
, “
Evidence of oscillatory convection inside an evaporating multicomponent droplet in a closed chamber
,”
J. Colloid Interface Sci.
378
,
260
262
(
2012b
).
26.
Manukyan
,
S.
,
Sauer
,
H. M.
,
Roisman
,
I. V.
,
Baldwin
,
K. A.
,
Fairhurst
,
D. J.
,
Liang
,
H.
,
Venzmer
,
J.
, and
Tropea
,
C.
, “
Imaging internal flows in a drying sessile polymer dispersion drop using spectral radar optical coherence tomography (SR-OCT)
,”
J. Colloid Interface Sci.
395
,
287
293
(
2013
).
27.
McNeilly
,
J. D.
, “
Application of evaporative coolers for gas turbine power plants
,” in
Proceedings of ASME Turboexpo: Power for Land, Sea, and Air
, 8–11 May, Munich, Germany (
ASME
,
2000
), Paper No. 2000-GT-303.
28.
Munoz
,
E. M.
,
Acros
,
J.
,
Bautista
,
O.
, and
Mendez
,
F.
, “
Influence of thermocapillary flow induced by a heated substrate on atomization driven by surface acoustic waves
,”
Phys. Fluids
35
,
012119
(
2023
).
29.
Nomura
,
H.
,
Ujiie
,
Y.
,
Rath
,
H. J.
,
Sato
,
I.
, and
Kono
,
M.
, “
Experimental study on high-pressure droplet evaporation using microgravity conditions
,”
Symp. (Int.) Combust.
26
,
1267
1273
(
1996
).
30.
Otsu
,
N.
, “
A threshold selection method from gray-level histograms
,”
IEEE Trans. Syst, Man Cybern.
9
,
62
66
(
1979
).
31.
Prasad
,
S.
,
Mandal
,
D. K.
, and
Narayanan
,
S.
, “
On the suppression of oscillatory circulation inside an evaporating bi-component drop through acoustic streaming
,”
Int. J. Multiphase Flow
129
,
103314
(
2020
).
32.
Prasad
,
S.
,
Narayanan
,
S.
, and
Mandal
,
D. K.
, “
Acoustic induced flow around an evaporating drop and its influence on internal circulation
,”
Int. J. Multiphase Flow
116
,
91
99
(
2019
).
33.
Radhakrishnan
,
S.
,
Anand
,
T. N. C.
, and
Bakshi
,
S.
, “
Evaporation-induced flow around a droplet in different gases
,”
Phys. Fluids
31
,
092109
(
2019
).
34.
Ristenpart
,
W. D.
,
Kim
,
P. G.
,
Domingues
,
C.
,
Wan
,
J.
, and
Stone
,
H. A.
, “
Influence of substrate conductivity on circulation reversal in evaporating drops
,”
Phys. Rev. Lett.
99
,
234502
(
2007
).
35.
Saito
,
M.
,
Sato
,
M.
, and
Suzuki
,
L.
, “
Evaporation and combustion of a single fuel droplet in acoustic fields
,”
Fuel
73
,
349
353
(
1994
).
36.
Sasaki
,
Y.
,
Kobayashi
,
K.
,
Hasegawa
,
K.
,
Kaneko
,
A.
, and
Abe
,
Y.
, “
Transition of flow field of acoustically levitated droplets with evaporation
,”
Phys. Fluids
31
,
102109
(
2019
).
37.
Savino
,
R.
and
Fico
,
S.
, “
Transient Marangoni convection in hanging evaporating drops
,”
Phys. Fluids
16
,
3738
3754
(
2004
).
38.
Singh
,
V.
,
Prasad
,
S.
,
Das
,
A.
,
Narayanan
,
S.
, and
Mandal
,
D. K.
, “
Effect of spacing on evaporation and internal circulation of two identical drops
,”
Europhys. Lett.
131
,
44001
(
2020
).
39.
Yamamoto
,
Y.
,
Abe
,
Y.
,
Fujiwara
,
A.
,
Hasegawa
,
K.
, and
Aoki
,
K.
, “
Internal flow of acoustically levitated droplet
,”
Microgravity Sci. Technol.
20
,
277
280
(
2008
).
40.
Yarin
,
A. L.
,
Brenn
,
G.
,
Kastner
,
O.
, and
Tropea
,
C.
, “
Drying of acoustically levitated droplets of liquid-solid suspension: Evaporation and crust formation
,”
Phys. Fluids
14
,
2289
2298
(
2002a
).
41.
Yarin
,
A. L.
,
Brenn
,
G.
, and
Rensink
,
D.
, “
Evaporation of acoustically levitated droplets of binary liquid mixtures
,”
Int. J. Heat Fluid Flow
23
,
471
486
(
2002b
).
42.
Zhao
,
S.
,
Liu
,
Z.
,
Wang
,
J.
,
Pang
,
Y.
,
Xue
,
S.
, and
Li
,
M.
, “
Formation of high-viscosity micro-droplets in T-channels with neck structure induced by surface acoustic waves
,”
Phys. Fluids
34
,
112012
(
2022
).

Supplementary Material

You do not currently have access to this content.