TY - JOUR
T1 - The role of viscosity on drop impact forces on non-wetting surfaces
AU - Sanjay, Vatsal
AU - Zhang, Bin
AU - Lv, Cunjing
AU - Lohse, Detlef
N1 - Publisher Copyright:
© The Author(s), 2025. Published by Cambridge University Press.
PY - 2025/1/30
Y1 - 2025/1/30
N2 - A liquid drop impacting a rigid substrate undergoes deformation and spreading due to normal reaction forces, which are counteracted by surface tension. On a non-wetting substrate, the drop subsequently retracts and takes off. Our recent work (Zhang et al., Phys. Rev. Lett., vol. 129, 2022, 104501) revealed two peaks in the temporal evolution of the normal force - one at impact and another at jump-off. The second peak coincides with a Worthington jet formation, which vanishes at high viscosities due to increased viscous dissipation affecting flow focusing. In this article, using experiments, direct numerical simulations and scaling arguments, we characterize both the peak amplitude F1 at impact and the one at takeoff (F2) and elucidate their dependency on the control parameters: the Weber number (dimensionless impact kinetic energy) and the Ohnesorge number (dimensionless viscosity). The first peak amplitude F1 and the time t1 to reach it depend on inertial time scales for low viscosity liquids, remaining nearly constant for viscosities up to 100 times that of water. For high viscosity liquids, we balance the rate of change in kinetic energy with viscous dissipation to obtain new scaling laws: F1/Fρ ∼ √Oh and, t1/τρ where Fρ and τρ are the inertial force and time scales, respectively, which are consistent with our data. The time t2 at which the amplitude F2 appears is set by the inertiocapillary time scale, τγindependent of both the viscosity and the impact velocity of the drop. However, these properties dictate the magnitude of this amplitude.
AB - A liquid drop impacting a rigid substrate undergoes deformation and spreading due to normal reaction forces, which are counteracted by surface tension. On a non-wetting substrate, the drop subsequently retracts and takes off. Our recent work (Zhang et al., Phys. Rev. Lett., vol. 129, 2022, 104501) revealed two peaks in the temporal evolution of the normal force - one at impact and another at jump-off. The second peak coincides with a Worthington jet formation, which vanishes at high viscosities due to increased viscous dissipation affecting flow focusing. In this article, using experiments, direct numerical simulations and scaling arguments, we characterize both the peak amplitude F1 at impact and the one at takeoff (F2) and elucidate their dependency on the control parameters: the Weber number (dimensionless impact kinetic energy) and the Ohnesorge number (dimensionless viscosity). The first peak amplitude F1 and the time t1 to reach it depend on inertial time scales for low viscosity liquids, remaining nearly constant for viscosities up to 100 times that of water. For high viscosity liquids, we balance the rate of change in kinetic energy with viscous dissipation to obtain new scaling laws: F1/Fρ ∼ √Oh and, t1/τρ where Fρ and τρ are the inertial force and time scales, respectively, which are consistent with our data. The time t2 at which the amplitude F2 appears is set by the inertiocapillary time scale, τγindependent of both the viscosity and the impact velocity of the drop. However, these properties dictate the magnitude of this amplitude.
KW - UT-Hybrid-D
KW - drops
UR - http://www.scopus.com/inward/record.url?scp=85216858309&partnerID=8YFLogxK
U2 - 10.1017/jfm.2024.982
DO - 10.1017/jfm.2024.982
M3 - Article
AN - SCOPUS:85216858309
SN - 0022-1120
VL - 1004
JO - Journal of fluid mechanics
JF - Journal of fluid mechanics
M1 - A6
ER -