Rarefied gas flow into vacuum through a long circular pipe composed of two sections of different radii

Abstract

Experiment on a one-way flow of a rarefied gas through a straight circular pipe without average temperature and pressure gradients AIP Conf.Abstract. The paper is devoted to the study of a rarefied gas flow through a composite circular pipe into vacuum. The pipe is made of two cylindrical sections of different diameters: narrower section is followed by the wider one (diverging configuration). The analysis is based on the direct numerical solution of the Boltzmann kinetic equation with the S-model collision integral. The results are presented for several length to radius ratios and a large range of Knudsen numbers. The main computed characteristic is the mass flow rate through the pipe. The dependence of the flow field on pipe's geometry and Knudsen number is established. Formation of special features of the flow, such as recirculation zones and a Mach disk, is studied.