Theory of nonequilibrium liquid–vapor interface: effects of shear flow

A theory of nonequilibrium interface structure is developed on the basis of the nonequilibrium ensemble method reported previously. A pair of integro-partial differential equations is presented for the nonequilibrium density profile of the Lennard–Jones fluid subjected to a steady shearing. The forms of the equations are mathematically similar to those in the equilibrium theory. A perturbation technique is employed to calculate the dynamic pair correlation function for a uniform fluid at a low shear rate. The underlying equilibrium theory of interface used is tested against the known results in the literature and found to be reliable. The nonequilibrium corrections arising from the shear flow to the density profile and the surface tension are calculated for different shear parameter values, and a “crossover” phenomenon is observed in density profile and surface tension, as the shear rate increases. Analysis of the transverse structure factor (or the susceptibility) is made to account for the changes in the interfacial properties arising from the nonequilibrium force.