Arlemark, E.J. and Dadzie, S.K. and Reese, J.M. (2010) An extension to the Navier-Stokes equations to incorporate gas molecular collisions with boundaries. Journal of Heat Transfer, 132 (4). 041006-1-041006-8. ISSN 0022-1481
We investigate a model for micro-gas-ﬂows consisting of the Navier-Stokes equations extended to include a description of molecular collisions with solid boundaries, together with ﬁrst and second order velocity slip boundary conditions. By considering molecular collisions aﬀected by boundaries in gas ﬂows we capture some of the near-wall eﬀects that the conventional Navier-Stokes equations with a linear stress/strain-rate relationship are unable to describe. Our model is expressed through a geometry-dependent mean-free-path yielding a new viscosity expression, which makes the stress/strain-rate constitutive relationship non-linear. Test cases consisting of Couette and Poiseuille ﬂows are solved using these extended Navier-Stokes equations, and we compare the resulting velocity proﬁles with conventional Navier-Stokes solutions and those from the BGK kinetic model. The Poiseuille mass ﬂow-rate results are compared with results from the BGK-model and experimental data, for various degrees of rarefaction. We assess the range of applicability of our model and show that it can extend the applicability of conventional ﬂuid dynamic techniques into the early continuum-transition regime. We also discuss the limitations of our model due to its various physical assumptions, and we outline ideas for further development.
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