gas mixing in a t-shape micro mixer has been simulated using the direct simulation monte carlo (dsmc) method. it is considered that the adequate mixing occurs when the mass composition of the species, co or n2, deviates below 1 % from their equilibrium composition. the mixing coefficient is defined as the ratio of the mixing length to the main channel’s height. as the inlet kn increases, while ...

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...

The numerical study of continuum-rarefied gas flows is of considerable interest because it can provide fundamental knowledge regarding flow physics. Recently, the nonlinear coupled constitutive method (NCCM) has been derived from the Boltzmann equation and implemented to investigate continuum-rarefied gas flows. In this study, we first report the important and detailed issues in the use of the ...

Rarefied gas phenomena are found in a wide variety of hypersonic flow applications, and accurate characterization of such phenomena is often desired for engineering design and analysis. In atmospheric flows involving high Mach numbers and/or low densities, underlying assumptions in a continuum fluid dynamics description tend to break down, and distributions of both molecule velocity and interna...

A recently established version of the discrete-ordinates method is used to develop a solution to a class of problems in the theory of rarefied-gas dynamics. In particular, an accurate solution for the flow, described by the Bhatnagar, Gross and Krook model, of a rarefied gas between two parallel plates is developed for a wide range of the Knudsen number.

The interaction of a diffusing outgas flow from a sphere nose opposing a hypersonic free stream is studied numerically using the direct simulation Monte-Carlo technique under the transitional rarefied-gas-flow regime conditions at Knudsen numbers from 0.016 to 1.5 and blowing factors from 0.15 to 1.5. Strong influences of the blowing factor (the ratio of outgas mass flux to upstream mass flux) ...

A fast synthetic type iterative model is proposed to speed up the slow convergence of discrete velocity algorithms for solving linear kinetic equations on triangular lattices. The efficiency of the scheme is verified both theoretically by a discrete Fourier stability analysis and computationally by solving a rarefied gas flow problem. The stability analysis of the discrete kinetic equations yie...

We propose the rarefied-gas-cushion model (r-GCM), as an extended version of the gas-cushion model (GCM), to estimate the apparent slip of water flowing over a gas layer trapped at a solid surface. Nanobubbles or gas nanofilms may manifest rarefied-gas effects and the r-GCM incorporates kinetic boundary conditions for the gas component in the slip Knudsen regime. These enable an apparent hydrod...

A gas inside the microsystems or the porous media is in its non-equilibrium state, due to the fact that the molecular mean free path is comparable to the characteristic dimension of the media. The same state of a gas, called rarefied, is found at high altitude or in the vacuum equipment working at low pressure. All these types of flow can be described by the kinetic models derived from the Bolt...