Gravitational effect in evaporating binary microdroplets

Yaxing Li, Christian Diddens, Pengyu Lv, Herman Wijshoff, Michel Versluis, Detlef Lohse (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

44 Downloads (Pure)

Abstract

The flow in an evaporating glycerol-water binary submillimeter droplet with a Bond number Bo 1 is studied both experimentally and numerically. First, we measure the flow fields near the substrate by microparticle image velocimetry for both sessile and pendant droplets during the evaporation process, which surprisingly show opposite radial flow directions - inward and outward, respectively. This observation clearly reveals that in spite of the small droplet size, gravitational effects play a crucial role in controlling the flow fields in the evaporating droplets. We theoretically analyze that this gravity-driven effect is triggered by the lower volatility of glycerol which leads to a preferential evaporation of water then the local concentration difference of the two components leads to a density gradient that drives the convective flow. We show that the Archimedes number Ar is the nondimensional control parameter for the occurrence of the gravitational effects. We confirm our hypothesis by experimentally comparing two evaporating microdroplet systems, namely, a glycerol-water droplet and a 1,2-propanediol-water droplet. We obtain different Ar, larger or smaller than a unit by varying a series of droplet heights, which corresponds to cases with or without gravitational effects, respectively. Finally, we simulate the process numerically, finding good agreement with the experimental results and again confirming our interpretation.

Original languageEnglish
Article number114501
Number of pages6
JournalPhysical Review Letters
Volume122
Issue number11
DOIs
Publication statusPublished - 18 Mar 2019

Fingerprint

gravitational effects
glycerols
water
flow distribution
evaporation
Bond number
radial flow
convective flow
volatility
microparticles
occurrences
gravitation
gradients

Cite this

Li, Yaxing ; Diddens, Christian ; Lv, Pengyu ; Wijshoff, Herman ; Versluis, Michel ; Lohse, Detlef. / Gravitational effect in evaporating binary microdroplets. In: Physical Review Letters. 2019 ; Vol. 122, No. 11.
@article{440a2e4318fd43c9b556b674aa47842f,
title = "Gravitational effect in evaporating binary microdroplets",
abstract = "The flow in an evaporating glycerol-water binary submillimeter droplet with a Bond number Bo 1 is studied both experimentally and numerically. First, we measure the flow fields near the substrate by microparticle image velocimetry for both sessile and pendant droplets during the evaporation process, which surprisingly show opposite radial flow directions - inward and outward, respectively. This observation clearly reveals that in spite of the small droplet size, gravitational effects play a crucial role in controlling the flow fields in the evaporating droplets. We theoretically analyze that this gravity-driven effect is triggered by the lower volatility of glycerol which leads to a preferential evaporation of water then the local concentration difference of the two components leads to a density gradient that drives the convective flow. We show that the Archimedes number Ar is the nondimensional control parameter for the occurrence of the gravitational effects. We confirm our hypothesis by experimentally comparing two evaporating microdroplet systems, namely, a glycerol-water droplet and a 1,2-propanediol-water droplet. We obtain different Ar, larger or smaller than a unit by varying a series of droplet heights, which corresponds to cases with or without gravitational effects, respectively. Finally, we simulate the process numerically, finding good agreement with the experimental results and again confirming our interpretation.",
author = "Yaxing Li and Christian Diddens and Pengyu Lv and Herman Wijshoff and Michel Versluis and Detlef Lohse",
year = "2019",
month = "3",
day = "18",
doi = "10.1103/PhysRevLett.122.114501",
language = "English",
volume = "122",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Physical Society",
number = "11",

}

Gravitational effect in evaporating binary microdroplets. / Li, Yaxing; Diddens, Christian; Lv, Pengyu; Wijshoff, Herman; Versluis, Michel; Lohse, Detlef (Corresponding author).

In: Physical Review Letters, Vol. 122, No. 11, 114501, 18.03.2019.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Gravitational effect in evaporating binary microdroplets

AU - Li, Yaxing

AU - Diddens, Christian

AU - Lv, Pengyu

AU - Wijshoff, Herman

AU - Versluis, Michel

AU - Lohse, Detlef

PY - 2019/3/18

Y1 - 2019/3/18

N2 - The flow in an evaporating glycerol-water binary submillimeter droplet with a Bond number Bo 1 is studied both experimentally and numerically. First, we measure the flow fields near the substrate by microparticle image velocimetry for both sessile and pendant droplets during the evaporation process, which surprisingly show opposite radial flow directions - inward and outward, respectively. This observation clearly reveals that in spite of the small droplet size, gravitational effects play a crucial role in controlling the flow fields in the evaporating droplets. We theoretically analyze that this gravity-driven effect is triggered by the lower volatility of glycerol which leads to a preferential evaporation of water then the local concentration difference of the two components leads to a density gradient that drives the convective flow. We show that the Archimedes number Ar is the nondimensional control parameter for the occurrence of the gravitational effects. We confirm our hypothesis by experimentally comparing two evaporating microdroplet systems, namely, a glycerol-water droplet and a 1,2-propanediol-water droplet. We obtain different Ar, larger or smaller than a unit by varying a series of droplet heights, which corresponds to cases with or without gravitational effects, respectively. Finally, we simulate the process numerically, finding good agreement with the experimental results and again confirming our interpretation.

AB - The flow in an evaporating glycerol-water binary submillimeter droplet with a Bond number Bo 1 is studied both experimentally and numerically. First, we measure the flow fields near the substrate by microparticle image velocimetry for both sessile and pendant droplets during the evaporation process, which surprisingly show opposite radial flow directions - inward and outward, respectively. This observation clearly reveals that in spite of the small droplet size, gravitational effects play a crucial role in controlling the flow fields in the evaporating droplets. We theoretically analyze that this gravity-driven effect is triggered by the lower volatility of glycerol which leads to a preferential evaporation of water then the local concentration difference of the two components leads to a density gradient that drives the convective flow. We show that the Archimedes number Ar is the nondimensional control parameter for the occurrence of the gravitational effects. We confirm our hypothesis by experimentally comparing two evaporating microdroplet systems, namely, a glycerol-water droplet and a 1,2-propanediol-water droplet. We obtain different Ar, larger or smaller than a unit by varying a series of droplet heights, which corresponds to cases with or without gravitational effects, respectively. Finally, we simulate the process numerically, finding good agreement with the experimental results and again confirming our interpretation.

UR - http://www.scopus.com/inward/record.url?scp=85063297363&partnerID=8YFLogxK

U2 - 10.1103/PhysRevLett.122.114501

DO - 10.1103/PhysRevLett.122.114501

M3 - Article

C2 - 30951342

AN - SCOPUS:85063297363

VL - 122

JO - Physical Review Letters

JF - Physical Review Letters

SN - 0031-9007

IS - 11

M1 - 114501

ER -