A general form of Macheret–Fridman classical impulsive dissociation model for nonequilibrium flows

2021 ◽  
Vol 33 (5) ◽  
pp. 056109
Author(s):  
N. Adhikari ◽  
A. A. Alexeenko
Keyword(s):  
Dissociation Model ◽  
Nonequilibrium Flows

Finite element adaptive method for hypersonic thermochemical nonequilibrium flows

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 1294-1302
Author(s):  
Djaffar Ait-Ali-Yahia ◽  
Wagdi G. Habashi
Keyword(s):  
Finite Element ◽  
Adaptive Method ◽  
Nonequilibrium Flows

Nonlinear dispersion hyperbolic models of continuous media

2007 ◽  
Vol 5 ◽  
pp. 273-278
Author(s):  
V.Yu Liapidevskii
Keyword(s):  
Boussinesq Equations ◽  
Nonlinear Dispersion ◽  
Order Of Accuracy ◽  
Flow Models ◽  
Wave Approximation ◽  
Long Wave ◽  
Primary Model ◽  
Nonequilibrium Flows ◽  
Internal Inertia ◽  
Long Wave Approximation

Nonequilibrium flows of an inhomogeneous liquid in channels and pipes are considered in the long-wave approximation. Nonlinear dispersion hyperbolic flow models are derived allowing taking into account the influence of internal inertia during the relative motion of phases upon the structure of nonlinear wave fronts. The asymptotic derivation of dispersion hyperbolic models is shown on the example of classical Boussinesq equations. It is shown that the hyperbolic approximation of the equations has the same order of accuracy as the primary model.

THE CONTRIBUTION OF THE BHATNAGAR–GROSS–KROOK MODEL TO THE DEVELOPMENT OF RAREFIED GAS DYNAMICS IN THE EARLY YEARS OF THE SPACE AGE

2013 ◽  
Vol 25 (01) ◽  
pp. 1340025
Author(s):  
RODDAM NARASIMHA
Keyword(s):  
Boltzmann Equation ◽  
Gas Dynamics ◽  
Rarefied Gas ◽  
Rarefied Gas Dynamics ◽  
Early Years ◽  
Plane Shock ◽  
Bgk Model ◽  
The Boltzmann Equation ◽  
Nonequilibrium Flows ◽  
Space Age

The advent of the space age in 1957 was accompanied by a sudden surge of interest in rarefied gas dynamics (RGD). The well-known difficulties associated with solving the Boltzmann equation that governs RGD made progress slow but the Bhatnagar–Gross–Krook (BGK) model, proposed three years before Sputnik, turned out to have been an uncannily timely, attractive and fruitful option, both for gaining insights into the Boltzmann equation and for estimating various technologically useful flow parameters. This paper gives a view of how BGK contributed to the growth of RGD during the first decade of the space age. Early efforts intended to probe the limits of the BGK model showed that, in and near both the continuum Euler limit and the collisionless Knudsen limit, BGK could provide useful answers. Attempts were therefore made to tackle more ambitious nonlinear nonequilibrium problems. The most challenging of these was the structure of a plane shock wave. The first exact numerical solutions of the BGK equation for the shock appeared during 1962 to 1964, and yielded deep insights into the character of transitional nonequilibrium flows that had resisted all attempts at solution through the Boltzmann equation. In particular, a BGK weak shock was found to be amenable to an asymptotic analysis. The results highlighted the importance of accounting separately for fast-molecule dynamics, most strikingly manifested as tails in the distribution function, both in velocity and in physical space — tails are strange versions or combinations of collisionless and collision-generated flows. However, by the mid-1960s Monte-Carlo methods of solving the full Boltzmann equation were getting to be mature and reliable and interest in the BGK waned in the following years. Interestingly, it has seen a minor revival in recent years as a tool for developing more effective algorithms in continuum computational fluid dynamics, but the insights derived from the BGK for strongly nonequilibrium flows should be of lasting value.

Computational Study on Radiative Aerothermodynamics of a Reentry Space Vehicle

2021 ◽  
Author(s):  
Qi Li ◽  
Sijun Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Computational Study ◽  
Space Vehicle ◽  
The Body ◽  
Stagnation Region ◽  
Convective Flux ◽  
Transit Times ◽  
Key Issues ◽  
Nonequilibrium Flows

Abstract Under hypersonic flight conditions, a vehicle travelling through the atmosphere could excite the air that flows around the body to very high temperatures as the kinetic energy of the vehicle is dissipated to the gas. Depending on the flight velocity, various chemical reactions will be produced behind a shock wave for stagnation region. These reactions greatly change the properties of air and cause considerable deviation from those of a thermally and calorically perfect gas. A vehicle flying through the higher altitude of the atmosphere at high velocities may also experience thermal non-equilibrium since the lower density reduces the collision frequency and the high velocity results in smaller transit times for the air molecules. Under such extremely thermal circumstances, the heat transfer by convection and radiation around a vehicle has been one of key issues for thermal protection system (TPS). In this paper, the computational aerothermodynamics with fully coupled radiative heat transfer is developed. To validate the proposed approach, it is employed to simulate the thermal and chemical nonequilibrium flows over Stardust. The computed results on the reentry space vehicle reveal both of convective flux and radiative flux are in good agreements with other predicted results.

Coulomb Dissociation of Nanoparticles Grazing along Organic Surfaces

2012 ◽  
Vol 67 (5) ◽  
pp. 296-302
Author(s):  
Viacheslav V. Komarov ◽  
Anna M. Popova ◽  
Lothar Schmidt ◽  
Hartmut Jungclas
Keyword(s):  
Small Molecules ◽  
Minimum Distance ◽  
Vibrational Energy ◽  
Coulomb Repulsion ◽  
Photon Flux ◽  
Coulomb Dissociation ◽  
Surface Molecules ◽  
Hydrocarbon Chains ◽  
Dissociation Model ◽  
Molecular Nanoparticles

A Coulomb dissociation model is presented for molecular nanoparticles, e.g. nanoclusters consisting of identical atoms or small molecules. These nanoparticles graze with velocities less than the Bohr velocity (108 cm=s) along an organic surface at atomic distances. The surface molecules contain IR-antennas, which consist of periodically located identical diatomic valence bonds with significant dipole momenta, e.g. hydrocarbon chains like (CH2)n. Here, we analyse the Coulomb interaction of these surface molecules with grazing nanoparticles, which do not contain any IR-antennas, e.g. fullerene molecules. Provided that the grazing velocity is in the range of 105 - 107 cm=s and the minimum distance of the grazing nanoparticles to the surface is approximately 2 Å , the IR-antennas of the interacting surface molecules will collect vibrational energy quanta, the so-called excimols. The number of excimols accumulated during the interaction time of at least 1 ps increases with the number of dipoles in the IR-antennas. Excimol energy can be transmitted back to the grazing nanoparticle by a ps-photon flux, which is estimated intense enough to induce multi-ionization of nanoparticle constituents. The resulting charges inside the nanoparticles cause high Coulomb repulsion forces, which will be able to promptly dissociate them.

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