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Simulation of rarefied micro to nano gas flows using improved slip flow models

Darbandi, M ; Sharif University of Technology | 2007

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  1. Type of Document: Article
  2. Publisher: 2007
  3. Abstract:
  4. If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the Navier-Stokes equations can be solved considering the concepts of slip flow regime and applying slip velocity boundary conditions at the solid walls. The high-order slip models can, in some cases, extend the range of applicability of the Navier-Stokes equations beyond Kn = 0.1, where the accuracy of first-order slip models starts deteriorating. To extend the capabilities of a macro-scale Navier-Stokes solver to micro and nano flow analysis, we benefit utilizing the modified high-order slip boundary conditions. It is shown that the extension is applicable to the entire Knudsen range while providing a second-order Kn accuracy in slip flow regimes. The present numerical approach is essentially a finite-volume method, which incorporates the advantages of finite-element method. We present an extensive comparison between DSMC, linearized Boltzmann, and the higher-order slip boundary model of a regular Navier-Stokes solver for hard sphere gases. The obtained results indicate that the use of high-order slip models can vigorously increase the capabilities of the large-scale Navier-Stokes solvers and can enable them to predict micro to nano flows with a wide range of Knudsen magnitudes
  5. Keywords:
  6. Hydrodynamic diameter ; Knudsen magnitudes ; Slip flow models ; Thermodynamic equilibrium ; Boltzmann equation ; Boundary conditions ; Flow velocity ; Mathematical models ; Navier Stokes equations ; Thermodynamic properties ; Flow of gases
  7. Source: 37th AIAA Fluid Dynamics Conference, Miami, FL, 25 June 2007 through 28 June 2007 ; Volume 1 , 2007 , Pages 576-583 ; 1563478978 (ISBN); 9781563478970 (ISBN)
  8. URL: https://arc.aiaa.org/doi/abs/10.2514/6.2007-3991