NONASYMPTOTIC CRITICAL-BEHAVIOR OF THE TRANSPORT-PROPERTIES OF FLUIDS

We extend the application of the mode-coupling theory for the dynamics of critical fluctuations in fluids into the non-asymptotic critical r egion. An approximate solution bf the mode-coupling equations yields a set of representative equations for the thermal conductivity and the viscosity of one-component fluids which incorporates the crossover fro m asymptotic singular behavior near the critical point to the regular behavior of these transport properties far away from the critical poin t. The equations for the critical enhancements of the thermal conducti vity and the viscosity depend on the background transport properties o f the fluid, the equilibrium thermodynamic properties of the fluid, an d one fluid-dependent wave-number cutoff q(D), which is indicative of the crossover length scale. We compare our crossover model with experi mental data for the thermal diffusivity, the thermal conductivity, and the viscosity of carbon dioxide and ethane. (C) 1995 American Institu te of Physics.