Investigation of the velocity fluctuation spectrum of a vortex flow of vibrationally excited molecular gas in a glow discharge

Gembarzhevskii, G. V.; Generalov, N. A.; Solov'ev, N.G.

doi:10.1007/bf02831430

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…In this density field, the gas compressibility is responsible for a reduction of the distance between vortices and for a frequency increase in the spectrum. This result corresponds to the experiment, 7 where frequency shift in nonequilibrium gas with respect to the equilibrium gas has been observed.…”

Section: -4supporting

confidence: 88%

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Influence of the initial vibrationally nonequilibrium state of a medium on the structure of von Karman vortex street

2006

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Numerical simulations of the flow of a vibrationally nonequilibrium gas around a circular cylinder have been undertaken. Distributions of velocity, temperature, and pressure in the wake behind the cylinder have been obtained, and the velocity fluctuation spectrum, which is measured in the experiment, has been examined. Three different models of medium and, accordingly, three different numerical schemes have been used. Comparison of the results enables one to identify the most important processes associated with the influence of relaxation, which result in some changes of the vortex street structure in comparison with the equilibrium case. Besides, such an approach enables one to verify the validity of the simplified methods used in numerical simulation of similar problems. Different conditions of heterogeneous relaxation on the surface of a cylinder are considered, and some comparison with experimental data is made.

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Section: -4supporting

confidence: 88%

“…In the experiment in Ref. 7, the fluctuation spectrum of the transverse velocity V y has been measured.…”

Section: Results Of Numerical Simulationmentioning

confidence: 99%

Influence of the initial vibrationally nonequilibrium state of a medium on the structure of von Karman vortex street

2006

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“…In its turn, heating leads to a decrease in the gas density in the vortices and their compression by the denser and colder surrounding gas. As a result of this effect, the fluctuations of the transverse velocity component V y , recorded experimentally [1], will be damped. This is a nonlinear effect since, as distinct from the sonic and thermal waves, in the linear approximation in the nonequilibrium gas the vortices are not damped and do not intensify since in the linear approximation the temperature and the density inside the vortex do not vary.…”

Section: Results Of the Numerical Simulationmentioning

confidence: 95%

“…The nonequilibrium effects can be very clearly demonstrated with reference to well-known gasdynamic flows, for example, the Kármán vortex street. In [1] the velocity fluctuation spectrum in a Kármán street was investigated experimentally and the equilibrium and nonequilibrium flow spectra were compared. The different effects of nonequilibrium on the fluctuation spectrum depending of the gas mixture composition and the probe location were observed.…”

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confidence: 99%

Karman Vortex Street in a Vibrationally Nonequilibrium Gas

Vinnichenko¹,

Nikitin²,

Uvarov³

2005

Fluid Dyn

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“…It was shown in [3][4][5][6], however, that stability decreases with increasing turbulence intensity. Within the framework of the problem considered, this phenomenon can be attributed to generation of heat waves.…”

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confidence: 97%

Interaction of Small Hydrodynamic Perturbations with a Nonequilibrium Region in a Gas Flow

Mukin

Осипов

Uvarov

2005

J Appl Mech Tech Phys

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The problem of interaction of small hydrodynamic perturbations with a nonequilibrium region in a gas flow with different models of energy pumping is solved. One-dimensional and two-dimensional interactions are considered. A range of system parameters is found in which interaction occurs in a resonant manner (significant amplification of perturbations is observed). It is demonstrated that interaction of vortex perturbations with the nonequilibrium region generates heat waves.Introduction. An important issue for continuous gas-flow lasers is hydrodynamic stability of the active medium. The starting point in the stability analysis is consideration of interaction of small hydrodynamic perturbations with a nonequilibrium region in the flow. Amplification of perturbations can be considered as the onset of instability.Gas-flow systems with a limited volume of the nonequilibrium gas region have two more factors, which are usually ignored in studying the evolution of small perturbations. The first factor is a localized energy contribution, which ensures the existence of a nonequilibrium region responsible for origination of gradients of thermodynamic parameters in the flow. The second factor is downstream entrainment of growing perturbations to the heated equilibrium region. The latter does not refer to acoustic perturbations. Acoustic waves can be reflected in a medium with gradients; in this case, the inhomogeneous zone itself can act as a resonator where the perturbations are amplified.The objective of the present work is to study the evolution of small hydrodynamic perturbations in a nonequilibrium region through which an initially equilibrium gas passes and to determine the range of perturbation frequencies in which the nonequilibrium region starts operating as a resonator.Formulation of the Problem. Regions of nonequilibrium states in terms of vibrational degrees of freedom are generated in a one-dimensional nonequilibrium gas flow by means of energy input. Two methods of energy pumping are considered:-Local input if the pumping region is much narrower than the relaxation zone; in this case, the pumping region can be considered as a surface on which the vibrational temperature changes in a jumplike manner;-Extended input if the pumping region has a finite width; the energy introduced into the flow is defined as a function I pump = I 0 exp (−(x − x 0 ) 2 /d), where the parameter d was chosen to be equal approximately to one third of the relaxation-zone length.Such a formulation of the problem corresponds to real conditions and allows one to estimate the effect of the pumping-region length. It is well known that part of the energy during pumping is spent on direct heating of the gas (bypassing vibrational degrees of freedom). It is possible to include this mechanism within the framework of approximations considered by introducing a source term into the energy equation for translational degrees of freedom. Nevertheless, the real kinetic scheme of such heating is rather complicated, and such a consideration is inexpedie...

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Investigation of the velocity fluctuation spectrum of a vortex flow of vibrationally excited molecular gas in a glow discharge

Cited by 4 publications

References 3 publications

Influence of the initial vibrationally nonequilibrium state of a medium on the structure of von Karman vortex street

Influence of the initial vibrationally nonequilibrium state of a medium on the structure of von Karman vortex street

Karman Vortex Street in a Vibrationally Nonequilibrium Gas

Interaction of Small Hydrodynamic Perturbations with a Nonequilibrium Region in a Gas Flow

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