Non-monotonic hydrodynamic lift force on highly extended polymers near surfaces
Department of Materials Science and Engineering, Massachusetts Institute of Technology 77 Mass. Ave. Cambridge MA 02139, USA
Accepted: 26 June 2011
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.
PACS: 83.80.Rs – Polymer solutions / 83.50.Ha – Flow in channels / 83.50.Lh – Slip boundary effects (interfacial and free surface flows)
© EPLA, 2011