To evaluate a lattice Boltzmann method (LBM) for the three dimensional continuum to non-continuum transitional flow regimes, the results are compared with those of the molecular dynamics (MD) simulations by the Leonard-Jones potential. The flow field considered is in a modeled nanoporous medium whose porosity is 0.88 and consists of square cylinder rods. The equations used in the LBM are modifi...

In this paper, we investigate the classic Graetz problem which is concerned with the thermal development length of a fluid flowing in a pipe or channel. In our particular study, we are interested in the thermal development length associated with a rarefied gas in a 2D channel. When the gas is in a rarefied state, the boundary conditions have to be modified to account for velocity-slip and tempe...

1 Introduction to the gas simulation methods The Navier-Stokes equations commonly encountered in fluid mechanics applications builds on the continuum approximation. When the ratio of the mean free path λ to the macroscopic length scale L, formalised by the non-dimensional Knudsen number Kn = λ/L, becomes large this approximation breaks down. The macroscopic length scale should be based on the l...

In this paper, we use a lattice Boltzmann model (LBM) for simulation of rarefied gas flows in microchannels at high and moderate Knudsen numbers. The lattice Boltzmann method uses D2Q9 lattice structure and BGK collision operator with single relaxation time. The solid wall boundary conditions used in this paper are based on the idea of bounceback of the nonequilibrium part of particle distribut...

abstract: since the field of micro electromechanical systems (mems) continues to grow, the flow in micro devices have become an area that receives a significant attention. the microscopic flows are usually characterized by the knudsen number (kn). when the characteristic size of the particle decreases down to a value comparable to the mean free path of the molecules, the continuum assumption fa...

We investigate oscillatory shear-driven gas flows in the transition and free-molecular-flow regimes. Analytical results valid through slip flow and the early transition regime are obtained using a recently proposed, rigorous second-order slip model with no adjustable coefficients. Analytical solution of the collisionless Boltzmann equation provides a description of the high Knudsen number limit...

Aerosol particle reactions with vapor molecules and molecular clusters are often collision rate limited, hence determination of particle-vapor molecule and particle-molecular cluster collision rates are of fundamental importance. These collisions typically occur in the mass transfer transition regime, wherein the collision kernel (collision rate coefficient) is dependent upon the diffusive Knud...

Inorganic nanopores occurring in the shale matrix have strong hydrophilicity and irreducible water (IW) film can be formed on inner surface of pores making gas flow mechanisms more complex. In this paper, existence inorganic is considered, and, based Knudsen number (Kn) correction pores, a apparent permeability model nano-pores established. The effect Kn permeability, ratio with pore radius IW ...

Hypersonic rarefied-gas flows near two side-byside plates have been studied numerically with the direct simulation Monte-Carlo technique under transitional rarefied-gas-flow conditions (Knudsen numbers from 0.024 to 1.8). Strong influences of the geometrical factor (ratio of distance between plates to plate length) and the Knudsen number on the flow structure (the shape of shock waves, the conf...

The slip correction factor has been investigated at reduced pressures and high Knudsen number using polystyrene latex (PSL) particles. Nano-differential mobility analyzers (NDMA) were used in determining the slip correction factor by measuring the electrical mobility of 100.7 nm, 269 nm, and 19.90 nm particles as a function of pressure. The aerosol was generated via electrospray to avoid multip...