Effusion of a dilute gas revisited: Van Kampen’s expansion

Abstract

We have studied the problem of effusion of a dilute gas through a hole by means of Van Kampen’s systematic Omega-expansion. In this way, the macroscopic equation as well as the Fokker-Planck equation for the fluctuations a round the macroscopic behaviour have been obtained and some dubious points in a recent analysis of the problem clarified.