Paper VT-TuP9
Scaling of Low-Pressure Transport Coefficients for Gas Mixture Flow in a Tube

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

Low pressure gas mixture flow in a tube can be analyzed with the linearized Boltzmann equation or the DSMC method. Alternatively, one can use the linearized Boltzmann equation to calculate gas transport coefficients that depend on the local concentration and density. These coefficients are then used in the gas flow analysis. This procedure requires repeated solution of the linearized Boltzmann equation, or preparation of coefficient tables for the whole range of expected gas concentrations and densities. Using the numerical results of Sharipov and Kalempa (J. Vac. Sci. Technol. A 20, 814 2002), we show how to rescale each transport coefficient for a gas mixture, collapsing the curves for various gas mixtures to a single curve. Once this re-scaling is done, to calculate the transport coefficients one needs the free-molecular value of the coefficient, the slip flow value, and interpolation of the dimensionless curve. This reduces the computational cost of the coefficient calculation to that of calculating the slip flow coefficients (for which relatively inexpensive methods are available) and interpolation of the dimensionless curves.