SHEAR LOCALIZATION IN SIMULATED FLUID

Shear localisation, in the form of discontinuities in the velocity pro file, can occur in simulated fluid, associated with a limit to the she ar stress. By modifying the thermostat, the occurrence of the plateau in the shear stress can be suppressed, resulting in a linear unconstra ined velocity profile. The shear rate dependence of the traction coeff icient 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'' i s found to occur in our hard-sphere model when the shear stress is lim ited, and where shear localisation also occurs, the string phase is re stricted to the shear localisation regions.