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Séminaire de Joshua D. McGraw

Hydrodynamic slip : origins and effects in micro- and nano-scopic polymer flows


Hydrodynamic slip : origins and effects in micro- and nano-scopic polymer
flows

Junior Research Chair
LabEx ENS-ICFP
Département de Physique
Ecole Normale Supérieure / PSL Research University, CNRS
24, rue Lhomond
75005 Paris, France

The hydrodynamic slip boundary condition encompasses fluid molecules
sliding against their confining boundary. The topic has been of
longstanding interest in the fluids community, but has also seen a surge
of recent interest due to its increased relevance in micro- and
nanoscopic fluid systems. In studying both the origins of slip and its
effect in different flow situations, polymer melts are ideal candidates.
Polymers are often solid at room temperature, allowing for ease of
manipulation, yet they have an easily accessible melting temperature. A
variety of micro- and nanoscopic flow situations on a variety of
substrates are then reachable. In this presentation, the origins and
effects of slip will be discussed. In the case of slip origins, we
address the effect of subnanometric substrate structural changes on the
slip boundary condition [1]. Remarkably, such small changes have a
pronounced and controllable effect on slip, pointing to slip’s truly
microscopic nature. In the case of slip effects, and armed with the
ability to change the slip boundary condition in a controlled way, we
systematically control the slip length for different micro- and
nanoscopic polymer flow situations. We are able to address slip’s
effects on contact line motion [2], the growth rates of hydrodynamic
instability [3], and its effect in direct force measurements of
lubrication flows.
[1] McGraw et al., J. Coll. Int. Sci. 210, (2014).
[2] McGraw et al., ArXiv:1507.03451 (2015).
[3] Haefner et al., Nat. Comm., (2015).

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