Dewetting film dynamics inside a capillary using a micellar nanofluid

Area of Science:

• Colloid and Surface Science
• Fluid Dynamics
• Nanotechnology

Background:

• Understanding fluid displacement in confined geometries is crucial for various industrial applications.
• Previous studies lacked detailed observation of film formation and dewetting dynamics during nanofluid displacement.
• The role of micelles in altering interfacial phenomena during displacement was not well-characterized.

Purpose of the Study:

• To experimentally investigate the displacement of hexadecane by a micellar nanofluid in a glass capillary.
• To characterize the novel film formation and dewetting phenomena observed.
• To develop a theoretical model for estimating dewetting velocity.

Main Methods:

• Experimental study involving hexadecane displacement by micellar nanofluid in a glass capillary.
• Observation and analysis of film formation, rupture, and droplet dynamics.
• Development of a theoretical model based on lubrication approximation and capillary pressure gradient.

Main Results:

• A thick, unstable hexadecane film formed on the capillary wall, which subsequently broke and retracted.
• Annular rims formed, leading to double-concave menisci and dewetting arrest, followed by droplet formation.
• The theoretical model showed fair agreement with experimentally measured annular rim dewetting velocities.

Conclusions:

• Micellar nanofluids induce unique dewetting phenomena, including unstable film formation and droplet generation, absent in micelle-free solutions.
• The observed process involves a sequence of film rupture, rim formation, and eventual droplet displacement.
• The developed theoretical model provides a reasonable estimation of the dewetting velocity in this complex system.