Statistical Mechanics of Transport Phenomena in Gases at Moderate Densities

A general method to expand the transport coefficients of dense gases in powers of the number density is developed, on the basis of the statistical mechanics of irreversible processes. The Ursell-Mayer expansion method is applied to the Liouville operator with use of the perturbation method which is reformulated for classical mechanics in this paper. This expansion method enables us to obtain the transport coefficients in the form of power series in the density. The exponential decay of the correlation functions of fluxes is obtained from the theory. The second approximation to the viscosity coefficient is obtained in the form which is useful for the numerical calculation.