DSMC simulation of rarefied gas mixtures flows driven by arrays of absorbing plates

Gas flows induced by arrays of absorbing surfaces of various shapes are met in several vacuum technology devices, like NEG or cryogenic pumps. In order to obtain a simplified model of low pressure gas dynamics driven by surface absorption, flows of rarefied gas binary mixtures past arrays of absorbing plates are studied by numerical solution of a system of coupled and spatially two-dimensional Boltzmann equations. The overall absorption rate is obtained as a function of problem parameters which include the characteristic flow Knudsen number and wall absorption probabilities. Particular attention is devoted to mixtures flows in which one of the components is present in small amounts and it is weakly absorbed.