Molecular gas dynamics and the direct simulation of gas flows

Steckelmacher, W

doi:10.1016/0042-207x(96)80021-2

Cited by 21 publications

(44 citation statements)

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“…The gas in the enclose is assumed to be monatomic with a viscosity µ related to the temperature T by µ = µ 0 (T /T 0 ) ω , where µ 0 is the reference viscosity at the reference temperature T 0 . The exponential index ω is set to be 0.81, corresponding to the variable hard sphere (VHS) model of argon gas at 273.15K [23]. The reference viscosity is defined using the VHS model [23,31],…”

Section: Simulation Setupmentioning

confidence: 99%

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

2017

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Rarefied gas flow in a three-dimensional enclosure induced by nonuniform temperature distribution is numerically investigated. The enclosure has a square channel-like geometry with alternatively heated closed ends and lateral walls with a linear temperature distribution. A recently proposed implicit discrete velocity method with a memory reduction technique is used to numerically simulate the problem based on the nonlinear Shakhov kinetic equation. The Knudsen number dependencies of the vortexes pattern, slip velocity at the planar walls and edges, and heat transfer are investigated. The influences of the temperature ratio imposed at the ends of the enclosure and the geometric aspect ratio are also evaluated. The overall flow pattern shows similarities with those observed in two-dimensional configurations in literature. However, new features due to the three-dimensionality are observed with new types of vortexes that are not identified in previous studies on similar twodimensional enclosures at high Knudsen and small aspect ratios.

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Section: Simulation Setupmentioning

confidence: 99%

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

2017

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“…II B. η p is the term leading the inverse power law of the repulsive collision model. For a hard sphere gas η p → ∞, and for the Lennard-Jones potential η p = 13 [12]. Kn is the Knudsen number:…”

Section: Introductionmentioning

confidence: 99%

“…The Knudsen number can only be assumed to be smaller than 0.2 in the space very close to the expansion origin (the nozzle), and hence the Navier-Stokes equations can't be generally used to model the flow of the beam close to, and after, the skimmer. Here, Direct Simulation Monte Carlo methods (DSMC), or direct numerical integration of the differential equation (under simplifying assumptions of the physics of the system), can be used to solve the Boltzmann equation [12,13].…”

Section: Introductionmentioning

confidence: 99%

Center-line intensity of a supersonic helium beam

et al. 2018

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Supersonic helium beams are used in a wide range of applications, for example surface scattering experiments and, most recently, microscopy. The high ionization potential of neutral helium atoms makes it difficult to build efficient detectors. Therefore, it is important to develop beam sources with a high centre line intensity. Several approaches for predicting the centre line intensity exist, with the so-called quitting surface model incorporating the largest amount of physical dependencies in a single analytical equation. However, until now only a limited amount of experimental data has been available. Here we present a comprehensive study where we compare the quitting surface model with an extensive set of experimental data. In the quitting surface model the source is described as a spherical surface from where the particles leave in a molecular flow determined by Maxwell-Boltzmann statistics. We use numerical solutions of the Boltzmann equation to determine the properties of the expansion. The centre line intensity is then calculated using an analytical integral. This integral can be reduced to two cases, one which assumes a continuously expanding beam until the skimmer aperture, and another which assumes a quitting surface placed before the aperture. We compare the two cases to experimental data with a nozzle diameter of 10 µm, skimmer diameters ranging from 4 µm to 390 µm, a source pressure range from 2 to 190 bar, and nozzleskimmer distances between 17.3 mm and 5.3 mm. To further support the two analytical approaches, we have also performed equivalent ray tracing simulations. We conclude that the quitting surface model predicts the centre line intensity of helium beams well for skimmers with a diameter larger than 120 µm when using a continuously expanding beam until the skimmer aperture. For the case of smaller skimmers the trend is correct, but the absolute agreement not as good. We propose several explanations for this, and test the ones that can be implemented analytically.

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“…1 In the NTC method, the volume of grid is used to compute the number of potential collisions within time interval. The collision rates in each grid is calculated by equation (4).…”

Section: Volume Calculationmentioning

confidence: 99%

“…1 The amount of dilution gas is determined by the Knudsen number (Kn). This parameter is a dimensionless number defined as the ratio of the molecular mean free path length to a representative physical length scale.…”

Section: Introductionmentioning

confidence: 99%

DgSMC-B code: A robust and autonomous direct simulation Monte Carlo code for arbitrary geometries

2016

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In this paper, we describe the structure of a new Direct Simulation Monte Carlo (DSMC) code that takes advantage of combinatorial geometry (CG) to simulate any rarefied gas flows Medias. The developed code, called DgSMC-B, has been written in FORTRAN90 language with capability of parallel processing using OpenMP framework. The DgSMC-B is capable of handling 3-dimensional (3D) geometries, which is created with first-and second-order surfaces. It performs independent particle tracking for the complex geometry without the intervention of mesh. In addition, it resolves the computational domain boundary and volume computing in border grids using hexahedral mesh. The developed code is robust and selfgoverning code, which does not use any separate code such as mesh generators. The results of six test cases have been presented to indicate its ability to deal with wide range of benchmark problems with sophisticated geometries such as airfoil NACA 0012. The DgSMC-B code demonstrates its performance and accuracy in a variety of problems. The results are found to be in good agreement with references and experimental data. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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Molecular gas dynamics and the direct simulation of gas flows

Cited by 21 publications

References 0 publications

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

Thermally induced rarefied gas flow in a three-dimensional enclosure with square cross-section

Center-line intensity of a supersonic helium beam

DgSMC-B code: A robust and autonomous direct simulation Monte Carlo code for arbitrary geometries

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