Rarefied Gas Dynamics

Коган, М. Н.

doi:10.1007/978-1-4899-6381-9

Cited by 879 publications

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“…[1][2][3][4][5] The reciprocal shock thickness in helium agrees reasonably well with the results of bimodal calculations 9 and with the few available experimental data.…”

Section: Salvador Monterosupporting

confidence: 78%

“…This is more or less in accordance with the general validity criteria for the continuum description, as obtained from the classical Chapman-Enskog expansion of Boltzmann equation. A discussion of these aspects has been given by Kogan, 1 Cercignani, 2 and others. [3][4][5] Moreover, due to the sparse experimental temperature and velocity data on welldefined 1D shock waves produced in shock tubes, little was known about the actual merits of NS equations to model the profiles of these quantities across the shock wave.…”

Section: Salvador Monteromentioning

confidence: 99%

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Numerical simulation of shock-wave structure for argon and helium

2005

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We compare the thickness of shock-wave fronts at different Mach numbers, modeled via NavierStokes ͑NS͒ equations, with experimental results from the literature. Monoatomic argon and helium are considered. In this modeling a finite-difference scheme with second-order spatial accuracy is employed. For argon the calculated density thickness is in good agreement with the experimental results. For helium the NS results agree well with those from the bimodal model and with the few available experimental data. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1921267͔The strong gradients within a shock-wave lead to a number of associated effects of scientific and technological relevance which have attracted the attention of theoreticians and experimentalists for a long time. Though the main features of shock waves are well understood, much remains to be done to complete the prediction of their quantitative aspects. The structure of a stationary shock wave has often been employed as a testing problem for numerical models of rarefied gas flows. In this context the one-dimensional ͑1D͒ shock waves produced in atomic argon and helium have been usual test systems to check the numerical aspects of NavierStokes ͑NS͒ equations by comparison with experiment.From the work done around 1950-1965 it was claimed that the NS approach could yield a reliable description of the density profile of the shock waves just up to Mach number Maϳ 2. This is more or less in accordance with the general validity criteria for the continuum description, as obtained from the classical Chapman-Enskog expansion of Boltzmann equation. A discussion of these aspects has been given by Kogan, 1 Cercignani, 2 and others. [3][4][5] Moreover, due to the sparse experimental temperature and velocity data on welldefined 1D shock waves produced in shock tubes, little was known about the actual merits of NS equations to model the profiles of these quantities across the shock wave. This limitation has prevailed up to now in spite of the wealth of density and temperature data on 2D shock waves produced in jets. 6,7 Unfortunately, 2D flows pose a number of difficulties for numerical modeling of normal shock waves ͑complicated flow pattern, low temperature upstream of the shock, with poorly known dependence of the viscosity on the temperature͒. Therefore, 2D shock waves are not well suited for use in connection with the simple 1D mathematical formulation.The main source of experimental 1D shock-wave density data suited for the present purpose has been compiled and completed with accurate original data by Alsmeyer. 8 In this work the experimental reciprocal thickness of argon and helium 1D shock waves is shown to be well characterized up to Ma= 10, while a few sparse helium data points have been included. Complete argon experimental density profiles were also reported by Alsmeyer for several MaϽ 10 values. Due to the shortage of experimental data on helium, the results of bimodal calculations have been also used as a reference, 9 since they are known to be quite rel...

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“…[1][2][3][4][5] The reciprocal shock thickness in helium agrees reasonably well with the results of bimodal calculations 9 and with the few available experimental data.…”

Section: Salvador Monterosupporting

confidence: 78%

Section: Salvador Monteromentioning

confidence: 99%

Numerical simulation of shock-wave structure for argon and helium

2005

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“…It is no surprise, then, that continuum-based methods (such as those based on perturbation series solutions of the Boltzmann equation) are unable to resolve properly the region of local non-equilibrium that exists up to one or two molecular mean free paths from the wall in any gas flow near a surface. Kogan (1969) demonstrated that the Chapman-Enskog technique (see Chapman & Cowling 1970) does not provide a solution to the Boltzmann equation in this 'Knudsen layer', or 'kinetic boundary layer', and Lockerby, Reese & Gallis (2005a) compared Knudsenlayer predictions from a number of current high-order equation sets and concluded that none could be considered both reliable and accurate. This is problematic for the future design and application of micro and nano flow devices because the momentum and energy fluxes from the region of the Knudsen layer to the boundaries have a critical influence on the overall flow behaviour.…”

Section: Introductionmentioning

confidence: 99%

On the modelling of isothermal gas flows at the microscale

Lockerby

Reese

2008

J. Fluid Mech.

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This paper makes two new propositions regarding the modelling of rarefied (nonequilibrium) isothermal gas flows at the microscale. The first is a new test case for benchmarking high-order, or extended, hydrodynamic models for these flows. This standing time-varying shear-wave problem does not require boundary conditions to be specified at a solid surface, so is useful for assessing whether fluid models can capture rarefaction effects in the bulk flow. We assess a number of different proposed extended hydrodynamic models, and we find the R13 equations perform the best in this case.Our second proposition is a simple technique for introducing non-equilibrium effects caused by the presence of solid surfaces into the computational fluid dynamics framework. By combining a new model for slip boundary conditions with a near-wall scaling of the Navier-Stokes constitutive relations, we obtain a model that is much more accurate at higher Knudsen numbers than the conventional second-order slip model. We show that this provides good results for combined Couette/Poiseuille flow, and that the model can predict the stress/strain-rate inversion that is evident from molecular simulations. The model's generality to non-planar geometries is demonstrated by examining low-speed flow around a micro-sphere. It shows a marked improvement over conventional predictions of the drag on the sphere, although there are some questions regarding its stability at the highest Knudsen numbers.

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“…Among the many available formulations of this kind of conditions, the ones proposed by Kogan [10] are used: …”

Section: Computational Fluid-dynamics (Cfd)mentioning

confidence: 99%

Analysis of Aero-Thermodynamic Behavior of EXPERT Capsule in Transitional Regime

Zuppardi¹,

Morsa²,

Schettino³

et al. 2011

AIP Conference Proceedings

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Abstract. The aerodynamic behavior of the EXPERT capsule has been already widely studied at low altitudes. In order to broaden the aerodynamic data base of the capsule, additional computations of the aerodynamic forces and an evaluation of the longitudinal stability and fluctuation of the pressure center have been carried out in the altitude interval 80-105 km. The effect of the rolling angle has been also evaluated. As EXPERT, in the considered altitude interval is in transitional regime, computations have been made by the DSMC code DS3V. Heat flux along the capsule surface has been also evaluated. This is an important topic because the nose and the frustum are made of low and high catalyticity materials, respectively. Computations, already performed in continuum regime by the CFD code H3NS, showed that, at the nose-frustum junction, an abrupt and strong peak of heat flux is present. In this work, this problem has been analyzed also in transitional regime. For this application, the DSMC 2-D code DS2V, requiring smaller computer resources, compared with the ones required by DS3V, has been used for making computations at lower altitudes. Furthermore, using DS2V made possible also to get a more detailed definition of the body surface and therefore to increase the surface resolution. The launch of the capsule is currently scheduled in 2011; flight data should be available to verify the results of the present computations.

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Rarefied Gas Dynamics

Cited by 879 publications

References 0 publications

Numerical simulation of shock-wave structure for argon and helium

Numerical simulation of shock-wave structure for argon and helium

On the modelling of isothermal gas flows at the microscale

Analysis of Aero-Thermodynamic Behavior of EXPERT Capsule in Transitional Regime

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