TY - JOUR
T1 - Oscillatory droplet dissolution from competing Marangoni and gravitational flows
AU - De La Cruz, Ricardo Arturo Lopez
AU - Diddens, Christian
AU - Zhang, Xuehua
AU - Lohse, Detlef
N1 - Funding Information:
The authors thank A. Marin and many other members of the Physics of Fluids group for valuable discussions about the experimental setup and in particular Y. Li for a very insightful discussion on the mechanism behind the mixing caused by the Marangoni flow. This work was supported by the European Union (ERC-Advanced Grant Project DDD No. 740479 and ERC-Proof-of-Concept Grant Project No. 862032). X.H.Z. acknowledges support from the Natural Sciences and Engineering Research Council of Canada - Discovery Project (NSERC) and from the Canada Research Chairs program. There is no conflict of interest for this work.
Publisher Copyright:
© 2022 American Physical Society.
PY - 2022/9/29
Y1 - 2022/9/29
N2 - The dissolution or growth of a droplet in a host liquid is an important part of processes like chemical extraction, chromatography, or emulsification. In this work we look at the dissolution of a pair of vertically aligned droplets immersed in water, both experimentally and numerically. The liquids used for the droplets are long chain alcohols with a low but finite solubility in water and a significantly lower density than that of the host liquid. Therefore, a solutal plume is formed above of the bottom droplet and natural convection dominates the dissolution process. We monitor the volume of the droplets and the velocity field around them over time. When the liquids of the two droplets are the same, our previously found scaling laws for the Sherwood and Reynolds numbers as functions of the Rayleigh number [Dietrich, J. Fluid Mech. 794, 45 (2016)0022-112010.1017/jfm.2016.158] can be applied to the lower droplet. However, remarkably, when the liquid of the top droplet is different than that of the bottom droplet the volume as function of time becomes nonmonotonic, and an oscillatory Marangoni flow at the top droplet is observed. We identify the competition between solutal Marangoni flow and density-driven convection as the origin of the oscillation and numerically model the process.
AB - The dissolution or growth of a droplet in a host liquid is an important part of processes like chemical extraction, chromatography, or emulsification. In this work we look at the dissolution of a pair of vertically aligned droplets immersed in water, both experimentally and numerically. The liquids used for the droplets are long chain alcohols with a low but finite solubility in water and a significantly lower density than that of the host liquid. Therefore, a solutal plume is formed above of the bottom droplet and natural convection dominates the dissolution process. We monitor the volume of the droplets and the velocity field around them over time. When the liquids of the two droplets are the same, our previously found scaling laws for the Sherwood and Reynolds numbers as functions of the Rayleigh number [Dietrich, J. Fluid Mech. 794, 45 (2016)0022-112010.1017/jfm.2016.158] can be applied to the lower droplet. However, remarkably, when the liquid of the top droplet is different than that of the bottom droplet the volume as function of time becomes nonmonotonic, and an oscillatory Marangoni flow at the top droplet is observed. We identify the competition between solutal Marangoni flow and density-driven convection as the origin of the oscillation and numerically model the process.
KW - 22/4 OA procedure
UR - https://www.scopus.com/pages/publications/85140141668
U2 - 10.1103/PhysRevFluids.7.094006
DO - 10.1103/PhysRevFluids.7.094006
M3 - Article
AN - SCOPUS:85140141668
SN - 2469-990X
VL - 7
JO - Physical review fluids
JF - Physical review fluids
IS - 9
M1 - 094006
ER -