Transport processes in dense gases

Abstract

A simple and direct procedure for evaluating the properties of dense gases has been attempted based on the BBGKY hierarchy of equations. The basic idea of Enskog, namely that increasing the density affects the behaviour of the assembly, mainly by reducing the specific volume and by providing a certain amount of shielding to molecular interactions, has been developed at length in this investigation. The decrease in specific volume allows one to approximate the three-particle distribution function in terms of one-particle and two-particle distribution functions. These distribution functions are expanded in terms of generalized Hermite polynomials to study small departures from equilibrium. In the simple Couette flow and one-dimensional heat flux problems, explicit expressions for viscosity and heat conductivity have been obtained. This enables one to study the variation of these with density and temperature. Numerical results are compared with experimental values for simple gases like argon, neon and helium. The values for the inverse-power-law forces behave monotonically and approach the Enskog curve. The Lennard-Jones potential shows, as density increases, an increase of viscosity and heat conductivity that is less rapid than for other power laws. The experimental values agrees well for the force laws studied here.