Rheology and diffusion in simple and complex fluids

Diffusion and rheology in a mixture of two simple or one simple and one com plex fluids are studied systematically in the framework of GENERIC modeling . The main result is a set of intrinsically consistent equations governing the time evolution of the overall mass density, overall momentum density (t his equation involves explicit formulae for the scalar hydrodynamic pressur e and the extra stress tensor), relative concentration of one fluid, diffus ion flux, and the microstructure of the complex fluid. In the process of so lving these equations we recover well-known results concerning the influenc e of stresses on diffusion and obtain new results concerning the influence of diffusion on stresses. (C) 1999 Elsevier Science B.V. All rights reserve d.