Gas Flows in the Transition and Free Molecular Flow Regimes

Abstract

We investigate pressure driven flow in the transition and free-molecular flow regimes with the objective of developing unified flow models for channels and ducts. These models are based on a velocity scaling law, which is valid for a wide range of Knudsen number. Simple slip-based descriptions of flowrate in channels and ducts are corrected for effects in the transition and free-molecular flow regimes with the introduction of a rarefaction coefficient. The resulting models can predict the velocity distribution, mass flowrate, pressure and shear stress distribution in rectangular ducts in the entire Knudsen flow regime.