Comparison of the Effect of Non-Random Surface Scattering on Free-Molecule and Slip Flow Through Capillaries

摘要

Classical theory predicts that forward scattering, as approximated by a fraction of specular reflections, has the same effect toward increasing both free-molecule and slip flows. A recent model by Berman using backscattering predicts that backscattering has nearly the same effect toward decreasing both free-molecule and slip flows. An analysis of the experimental data of Lund and Berman, and that of Knudsen, is given which indicates that the effect is different for free-molecule flow than for slip flow. An alternative calculation for the effect of both specular reflections and backscattering on free-molecule flow is given. This calculation predicts a different effect for free-molecule flow than for slip flow. The calculation also agrees somewhat better with the experimental data. (ERA citation 06:012667)