Inertial capillary uptake of drops

Area of Science:

• Fluid dynamics
• Surface science
• Materials science

Background:

• Capillary action drives liquid uptake into narrow tubes.
• Understanding liquid behavior in microchannels is crucial for various applications.

Purpose of the Study:

• To experimentally investigate and quantitatively analyze the uptake of liquid drops into capillary tubes.
• To determine the factors influencing uptake velocity, including drop curvature and fluid properties.

Main Methods:

• High-speed imaging (4000 fps) to measure meniscus height rise.
• Experiments using water and glycerol solutions in glass and quartz capillaries.
• Analysis within the inertial regime to define uptake velocity.

Main Results:

• Observed constant uptake velocity in the inertial regime.
• Inertial velocity increased with drop curvature due to Laplace pressure.
• Measured velocities were slower than predicted by purely inertial-capillary models.
• Contact line friction was introduced to explain viscosity dependence and variability.
• Friction coefficients in borosilicate capillaries ranged from 169±1 to 218±1.
• Surface oscillation-induced Laplace pressure peaks correlated with uptake velocity.

Conclusions:

• Contact line friction is a critical factor in liquid uptake into capillaries.
• Laplace pressure and surface oscillations play a role in uptake dynamics.
• The findings provide a more accurate model for liquid drop entry into tubes.