Rarefied Gas Flow through Tubes of Finite Length

The flow of rarefied gases through tubes of finite length due to a pressure gradient is investigated by the Direct Simulation Monte Carlo (DSMC) method. The non-equilibrium effects at the inlet and outlet of the tube have been considered by including in the computational domain large volumes of the upstream and downstream reservoirs. In addition, to improve the efficiency of the DSMC method, a non-uniform grid and several weighting zones in the axial and radial directions are implemented. Results are presented in dimensionless form and include the flow rate and several quantities of the flow field in terms of various values of the outlet to inlet pressure ratio and of the length to radius ratio in the whole range of the Knudsen number.