NONLINEAR MASS AND MOMENTUM TRANSPORT IN A DILUTE GAS

Far from equilibrium particle and momentum transport in a binary mixture subject to uniform shear flow is analyzed. Particles of each species are labeled by a "color charge." Mutual diffusion is created by the action of an external field that accelerates particles of different species along opposite directions. For a dilute gas of Maxwell molecules, the set of two coupled Boltzmann equations is seen to be solvable by the moment method. The color conductivity tensor and the shear viscosity coefficient are obtained as nonlinear functions of the shear rate and the color field. The usual choice of the external color field [Cummings et al., J. Chem. Phys. 94, 2149 (1991)] yields a zero-field limit of the color conductivity tensor different from the self-diffusion tensor. In order to avoid the above discrepancy, a different form of the external field is proposed.