An interferometric study of spreading liquid films

Moving contact line problems involving polymeric materials and other complex fluids are encountered in many applications such as coating flows, gravity-driven drainage, and spin-coating operations. Viscous, capillary, inertial and gravitational forces can all be important in these flows depending on the scale and speed of the spreading process. In this research, a number of benchmark problems involving moving contact lines of viscous Newtonian and non-Newtonian polymeric fluids have been studied using non-invasive optical techniques. A detailed study of viscous Newtonian and non-volatile liquids spreading on smooth horizontal and inclined substrates is presented. A phase-modulated interference microscope was used to enable the simultaneous measurement of both the inner (microscopic) length scale and the outer (macroscopic) flow scale in addition to the intermediate matching region. The resulting measurements of both the apparent contact angle and lateral scale of the precursor wetting film agree quantitatively with theoretical predictions for the spreading of a van der Waals fluid over a wide range of capillary numbers (10-6 < Ca < 10-1). It is also shown that the dynamic contact angle of a perfectly wetting Newtonian fluid is not only a function of the capillary number (the Hoffman-Voinov-Tanner law), but also depends on a logarithmic correction to this relationship, which is often overlooked. It is shown that both the microscopic and macroscopic length scales affect this logarithmic correction. Our measurements are in good quantitative agreement with available theoretical predictions. In addition to the steady, isothermal spreading of fluids, we have studied instabilities of volatile liquid films spreading on thermally conductive surfaces.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Kavehpour, Hossein Pirouz

Advisor dc:contributor.advisor

• Gareth H. McKinley.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29635

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29635