DEPENDENCE OF SLIP COEFFICIENT ON FORM OF COLLISION FREQUENCY

The slip coefficient for a gas is computed for certain typical forms of the collision frequency. The computations are made by a numerical quadrature based on an exact formula and also by a variational procedure. There is a good agreement between the results obtained by both methods and between them and previously known results. Our calculations confirm that the slip coefficient is only slightly model dependent. It is also shown that, for any form of the collision frequency, the slip-coefficient dependence on the accommodation coefficient for tangential momentum can be found analytically, in terms of the value corresponding to complete accommodation. © 1968 Società Italiana di Fisica.