Title: Capillary spreading of contact line over a sinking sphere

Abstract

The contact line dynamics over a sinking solid sphere are investigated in comparison with classical spreading theories. Experimentally, high-speed imaging systems with optical light or x-ray illumination are employed to accurately measure the spreading motion and dynamic contact angle of the contact line. Millimetric spheres are controlled to descend with a constant speed ranging from 7.3 × 10-5 to 0.79 m/s. We observed three different spreading stages over a sinking sphere, which depends on the contact line velocity and contact angle. These stages consistently showed the characteristics of capillarity-driven spreading as the contact line spreads faster with a higher contact angle. The contact line velocity is observed to follow a classical capillary-viscous model at a high Ohnesorge number (> 0.02). For the cases with a relatively low Ohnesorge number (< 0.02), the contact line velocity is significantly lower than the speed predicted by the capillary-viscous balance. This indicates the existence of an additional opposing force (inertia) for a decreasing Ohnesorge number. The capillary-inertial balance is only observed at the very beginning of the capillary rise, in which the maximum velocity is independent of the sphere’s sinking speed. Additionally, we observed the linear relation between the contact line velocity and themore » sphere sinking speed during the second stage, which represents capillary adjustment by dynamic contact angle.« less

Authors:

Kim, Seong Jin ;

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Fezzaa, Kamel; An, Jim; Sun, Tao; Jung, Sunghwan

Publication Date:

2017-09-25

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

National Science Foundation (NSF); USDOE Office of Science (SC)

OSTI Identifier:

1411172

DOE Contract Number:  

AC02-06CH11357

Resource Type:

Journal Article

Journal Name:

Applied Physics Letters

Additional Journal Information:

Journal Volume: 111; Journal Issue: 13; Journal ID: ISSN 0003-6951

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS