Non-monotonic hydrodynamic lift force on highly extended polymers near surfaces

• Published in: Europhysics letters Vol. 95; no. 4; p. 48001
• Main Authors: Sing, C. E., Alexander-Katz, A.
• Format: Journal Article
• Language: English
• Published: EPS, SIF, EDP Sciences and IOP Publishing 01.08.2011
• Subjects: 83.50.Ha; 83.50.Lh; 83.80.Rs
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/95/48001

The hydrodynamic lift force that polymers experience near boundaries is known to be a crucial element when considering rheological flows of dilute polymer solutions. Here we develop a theory to describe the hydrodynamic lift force on extended polymers flowing near flat surfaces. The lift force is shown to display a non-monotonic character increasing linearly with the distance to the wall Z in the near-surface regime defined as Z<L, with L being the contour length of the polymer. At heights Z∼L the lift force displays a maximum, and for Z>L we recover the well-known far-field result in which the force decays as Z−2. Our analytical theory has important implications in understanding adsorption, desorption, and depletion layers of highly extended objects in flow.