Rarefied gas flow in pressure and vacuum measurements

Rarefied Background Flow in a Vacuum Chamber

Spacecraft propulsion systems, such as Hall thrusters, are designed and tested in large vacuum chambers. The pumping capacity of modern facilities makes it possible to maintain pressures as low as 3 10 4 10 Pa. In this study, several free molecular models are developed to analyze the background flow inside a vacuum chamber. These models lead to various sets of analytical results including veloc...

Rarefied gas dynamics and its applications to vacuum technology

Basic concepts of rarefied gas dynamics are given in a concise form. Some problems of rarefied gas flows are considered, namely, calculations of velocity slip and temperature jump coefficients, gas flow through a tube due to pressure and temperature gradients, and gas flow through a thin orifice. Results on the two last problems are given over the whole range of gas rarefaction. A methodology f...

Gas-kinetic scheme for rarefied flow simulation

For increasingly rarefied flowfields, the predictions from continuum formulation, such as the Navier–Stokes equations lose accuracy. These inaccuracies are attributed primarily to the linear approximations of the stress and heat flux terms in the Navier– Stokes equations. The inclusion of higher order terms, such as Burnett, or high-order moment equations, could improve the predictive capabilit...

Rarefied gas flows through meshes and implications for atmospheric measurements

Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flo...

Rarefied gas flow in microtubes at different inlet-outlet pressure ratios