TY - JOUR
T1 - Numerical Interpretation to the Roles of Liquid Viscosity in Droplet Spreading at Small Weber Numbers
AU - Zhang, Zhenyu
AU - Zhang, Peng
N1 - Funding Information:
This work at Beijing Institute of Technology was supported by the National Natural Science Foundation of China (grant no. 51806013) and Beijing Institute of Technology Research Fund Program for Young Scholars (grant no. 2019CX04031). The work at the Hong Kong Polytechnic University was supported by the Hong Kong Research Grants Council/General Research Fund (PolyU 152217/14E and PolyU 152651/16E) and partly by the Central Research Grant (G-SB1Q).
Funding Information:
This work at Beijing Institute of Technology was supported by the National Natural Science Foundation of China (grant no. 51806013) and Beijing Institute of Technology Research Fund Program for Young Scholars (grant no. 2019CX04031). The work at the Hong Kong Polytechnic University was supported by the Hong Kong Research Grants Council/General Research Fund (PolyU 152217/14E and PolyU 152651/16E) and partly by the Central Research Grant (G-SB1Q).
Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2019/12/10
Y1 - 2019/12/10
N2 - Droplet impacting a free-slip plane at small Weber numbers (We < 30) was numerically investigated by a front tracking method, with particular emphasis on clarifying the roles of the liquid viscosity and the "left-over" internal kinetic energy in droplet spreading. The most interesting discovery is that there exists a certain range of We in which the maximum diameter rate, Dm, shows a nonmonotonic variation with the Reynolds number, Re. This non-monotonic variation is owing to the dual role of liquid viscosity in influencing droplet spreading. Specifically, when the initial surface energy is comparable to the initial kinetic energy (the corresponding We is around 10-30), the high strain rates of the droplet internal flow dominate its viscous dissipation at a relatively large Re, while the liquid viscosity dominates the viscous dissipation at a relatively small Re. Furthermore, to unravel the influence of droplet attachment and detachment on droplet spreading, we considered two limiting situations such as full attachment (with no gas film throughout droplet spreading) and full detachment (with a gas film throughout droplet spreading). The results show that the droplet with a gas film tends to generate a stronger vortical motion in its rim, results in a larger left-over kinetic energy, and hence causes a smaller spreading.
AB - Droplet impacting a free-slip plane at small Weber numbers (We < 30) was numerically investigated by a front tracking method, with particular emphasis on clarifying the roles of the liquid viscosity and the "left-over" internal kinetic energy in droplet spreading. The most interesting discovery is that there exists a certain range of We in which the maximum diameter rate, Dm, shows a nonmonotonic variation with the Reynolds number, Re. This non-monotonic variation is owing to the dual role of liquid viscosity in influencing droplet spreading. Specifically, when the initial surface energy is comparable to the initial kinetic energy (the corresponding We is around 10-30), the high strain rates of the droplet internal flow dominate its viscous dissipation at a relatively large Re, while the liquid viscosity dominates the viscous dissipation at a relatively small Re. Furthermore, to unravel the influence of droplet attachment and detachment on droplet spreading, we considered two limiting situations such as full attachment (with no gas film throughout droplet spreading) and full detachment (with a gas film throughout droplet spreading). The results show that the droplet with a gas film tends to generate a stronger vortical motion in its rim, results in a larger left-over kinetic energy, and hence causes a smaller spreading.
UR - http://www.scopus.com/inward/record.url?scp=85076325520&partnerID=8YFLogxK
U2 - 10.1021/acs.langmuir.9b02736
DO - 10.1021/acs.langmuir.9b02736
M3 - Journal article
C2 - 31718189
AN - SCOPUS:85076325520
SN - 0743-7463
VL - 35
SP - 16164
EP - 16171
JO - Langmuir
JF - Langmuir
IS - 49
ER -