Shear localisation in simulated fluid

¹ Department of Physics and Astronomy, Edinburgh University, King's Buildings, Edinburgh EH9 3JZ, UK
² Shell Research Ltd.,Thornton Research Centre, P.O. Box 1 - Chester CH1 3SH, UK

Received: 5 December 1998
Accepted: 13 July 1998

Abstract

Shear localisation, in the form of discontinuities in the velocity profile, can occur in simulated fluid, associated with a limit to the shear stress. By modifying the thermostat, the occurrence of the plateau in the shear stress can be suppressed, resulting in a linear unconstrained velocity profile. The shear rate dependence of the traction coefficient leads to a limiting value of the traction coefficient even when the shear stress is unbounded. Simulations thus give insight into the molecular basis of the limiting shear stress behaviour in lubricants. The shear-induced positional ordering known as the “string phase” is found to occur in our hard-sphere model when the shear stress is limited, and where shear localisation also occurs, the string phase is restricted to the shear localisation regions.