共查询到20条相似文献,搜索用时 859 毫秒
1.
A shock tube experimental investigation and numerical simulations are undertaken to study the evolution of a perturbed interface of two different gases accelerated by a shock wave. The experimental method is based on a high-speed camera laser sheet diagnostic technique, and simulations are provided by our code CARBUR based on a finite volume discretization of Navier–Stokes’s equations. Two gas pairs are used to illustrate both the heavy/light (air/He) and the light/ heavy (air/SF6) cases. Two simultaneous large initial perturbations, one positive and one negative, are tested for an incident shock wave Mach number in air of about 1.3. The thin membrane (less than 1 μ) which materializes the initial interface between the two test gases presents 2D perturbations whose wave number is close to 1 in order to rapidly reach the non-linear regime. The development of the perturbations is captured at a frequency of 10 kHz after the interface acceleration, and the experiments are complemented with a numerical simulation to validate the interface deformations. Results show an asymmetric mutual gas penetration increasing with the absolute value of the Atwood’s number. Furthermore, they confirm that the heavier gas penetrates the lighter as thin spikes and the lighter gas penetrates the heavier as large bubbles. Moreover, we show that the spike moves faster than the bubble in the heavy/light case and slightly faster in the light/heavy one. Finally, numerical and experimental results are in agreement. 相似文献
2.
It was recently demonstrated that shock wave enhancement could be achieved when a shock propagates in a constant cross-section
duct through pairs of air–helium layers having a continually decreasing width (Igra and Igra in Shock Waves 16(3):199–207).
A parametric study was conducted aimed at finding a two-layered, light–heavy gas arrangement that yields maximal shock enhancement;
the heavy and the light gases used were air and helium, respectively. Effects associated with changes in following parameters
were investigated: the number of alternating heavy/light gas layers, the applied reduction ratio between successive layers
thickness, and the initial shock wave Mach number.
相似文献
3.
A. S. Vereshchagin S. N. Vereshchagin V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2007,48(3):375-384
A mathematical model is constructed and an analytical solution is obtained for the problem of a one-dimensional steady flow
of a mixture of different gases with hollow permeable particles. The case of a one-dimensional unsteady flow of such a mixture
is analyzed numerically. The numerical solutions are compared with experimental data on the motion of the peak concentration
of helium in a fixed bed filled with cenospheres (solid hollow permeable spherical particles). The permeability of cenosphere
walls and the drag coeficient of cenospheres in the gas flow are determined.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 92–102, May–June, 2007. 相似文献
4.
A collision of supersonic flows of gas mixtures with disparate molecular weights, which are limited in their cross-sectional
size, in vacuum leads to formation of a cloud with an elevated concentration and elevated temperature of the heavy gas. Under
certain conditions, the governing factor is the collision of molecules of the heavy gas being compressed at the center of
the collision of the flows. The generator of such a flow can be called a collider. Results of studying the flows in jet-type,
cylindrical, and mixed two-stage colliders are described. The main attention is paid to separation of gases in terms of energy
and composition.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 142–151, May–June, 2007. 相似文献
5.
The behavior of the vorticity vector on a discontinuity surface arising in a supersonic nonuniform combustible gas flow with
the formation of a shock or detonation wave is studied. In the general case, it is a vortex flow with prescribed distributions
of parameters. It is demonstrated that the ratio of the tangential component of vorticity to density remains continuous in
passing through the discontinuity surface, while the quantities proper become discontinuous. Results calculated for flow vorticity
behind a steady-state detonation wave in an axisymmetric supersonic flow of a combustible mixture of gases are presented.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 15–21, November–December, 2007 相似文献
6.
We study the Boltzmann equation for a mixture of two gases in one space dimension with initial condition of one gas near vacuum
and the other near a Maxwellian equilibrium state. A qualitative-quantitative mathematical analysis is developed to study
this mass diffusion problem based on the Green’s function of the Boltzmann equation for the single species hard sphere collision
model in Liu andYu (Commun Pure Appl Math 57:1543–1608, 2004). The cross-species resonance of the mass diffusion and the diffusion-sound
wave is investigated. An exponentially sharp global solution is obtained. 相似文献
7.
A distributed mathematical model is proposed to describe a flow of a mixture of gases, fine particles of a reacting metal,
and droplets of a hydrocarbon fuel. The heterogeneous chemical reaction of low-temperature oxidation of the metal, the homogeneous
oxidation reaction of the reacting vaporized liquid fuel, and the difference in phase velocities and temperatures are taken
into account. It is shown that this model can be used to describe the problems of detonation in a mixture of a reacting gas
and reacting solid particles, and the problems of ignition of a mixture of aluminum particles and tridecane droplets.
Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated
from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 2, pp. 128–136, March–April, 1999. 相似文献
8.
G. A. Ruev A. V. Fedorov V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2005,46(3):307-314
Based on the previously formulated mathematical model of mechanics of a two-velocity two-temperature mixture of gases, the
evolution of an initially disturbed mixing layer of two gases with different densities under the action of shock waves is
considered in a two-dimensional unsteady approximation. Problems of interaction of shock waves with a sinusoidally disturbed
diffuse layer are solved numerically. The predicted variation of the mixing-region width are in satisfactory agreement with
experimental data.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 3–11, May–June, 2005. 相似文献
9.
Yu. N. Voroshilova M. A. Rydalevskaya 《Journal of Applied Mechanics and Technical Physics》2008,49(3):369-374
A formula for the velocity of sound, which is valid not only for barotropic gases, is derived on the basis of methods of the
kinetic theory of gases. This formula is specified for various stages of relaxation of a high-temperature diatomic gas in
the approximation of the model of anharmonic oscillators. A dependence between the populations of vibrational levels of molecules
and the velocity of sound is found.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 28–34, May–June, 2008. 相似文献
10.
Diffraction of cellular heterogeneous detonation out of a channel into open half-space in a mixture of aluminum particles
and oxygen is investigated numerically. The flow is found to be very similar to gas detonation diffraction. The detonation
weakening behind the step results in combustion front deceleration and decoupling from the leading shock wave. Subsequent
re-initiation takes place in a transverse wave. New transverse waves are generated along the expanding front. The computations
that were performed show that the critical number of cells is several times less than that for gases. This is confirmed by
theoretical estimates based upon the Mitrofanov–Soloukhin approach. 相似文献
11.
This paper is a contribution to the development of an original technique for measuring the in-cylinder equivalence air–fuel
ratio. The main objective was to construct an instrument able to furnish instantaneous values of hydrocarbon concentration
for many consecutive cycles at a definite location, especially at the spark plug location. The probe is based on a hot-wire-like
apparatus, but involves catalytic oxidation on the wire surface in order to be sensitive to the hydrocarbon concentration.
In this paper, we present the different steps needed to develop and validate the probe. The first step focuses on the geometric
configuration to simplify as much as possible the mass transfer phenomena on the wire. The second step is a parametric study
to evaluate the sensitivity, confidence and lifetime of the wire. By physical analysis, we propose a relationship between
the electrical signal and the air–fuel equivalence ratio of the sampled gases. The third step is the application of the probe
to in-cylinder motored engine measurements, which confirms the ability of the technique to characterise, quantitatively, the
homogeneity of the air–fuel mixture, especially during the compression stroke. This work points out that the global sensitivity
is estimated at 4 V per unit of equivalence air–fuel ratio and the response time is estimated at about 400 μs. The equivalence
air–fuel ratio range is from pure air to 1.2. Experiments show that it is necessary to calibrate the system before use because
of the existence of multiple catalysis states. The probe presents advantages associated with its simplicity, its low cost
and its direct engine application without any modifications.
Received: 1 November 2000 / Accepted: 30 May 2001 相似文献
12.
The high-speed combustible gas ignited by a hot gas jet, which is induced by shock focusing, was experimentally investigated. By use of the separation mode of shock tube, the test section of a single shock tube is split into two parts, which provide the high-speed flow of combustible gas and pilot flame of hot gas jet, respectively. In the interface of two parts of test sections the flame of jet was formed and spread to the high-speed combustible gas. Two kinds of the ignitions, 3-D “line-flame ignition” and 2-D “plane-flame ignition”, were investigated. In the condition of 3-D “line-flame ignition” of combustion, thicker hot gas jet than pure air jet, was observed in schlieren photos. In the condition of 2-D “plane-flame ignition” of combustion, the delay time of ignition and the angle of flame front in schlieren photos were measured, from which the velocity of flame propagation in the high-speed combustible gas is estimated in the range of 30–90m/s and the delay time of ignition is estimated in the range of 0.12–0.29ms.
PACS 47.40.Nm; 82.40.FpPart of this paper was presented at the 5th International Workshop on Shock/Vortex Interaction, Kaohsiung, October 27–31, 2003. 相似文献
13.
The flow velocity fluctuations in a gas laser are measured under non-self-maintained glow discharge conditions. Spectra of
the pulsating velocity signal on the frequency interval up to 2 kHz and the time dependence of the signal under glow and neutral
flow conditions for pure nitrogen, a mixture of nitrogen and helium, and a trial CO2-N2-He mixture are obtained. Deformation (due to the action of the discharge) of the spectra of the transverse velocity component
in the wake of a right circular cylinder is observed. In order to analyze the data obtained a model of the dynamic response
of the pulsating velocity is constructed and a model of the Kármán vortex street behind a body is generalized with allowance
for variations of the oscillation phase in the street.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 81–91, March–April, 2000.
The work was carried out with partial financial support from the Russian Foundation for Basic Research (projects Nos. 96-01-00372
and 99-01-01199). 相似文献
14.
The enhancement of heat transfer in natural convection cavities is a very difficult task because of the intervening low fluid
velocities. It is of fundamental and practical interest to explore alternative instruments that are power-independent and
exclude surface modifications for the augmentation of heat transfer in these cavities. One feasible way for enhancing heat
transfer rates passively in cavities filled with a gas is to stimulate the mechanism by natural convection of heat. The central
objective of this paper is to employ a mixture of two pure gases that yields levels of heat transfer increments that are unattainable
by each pure gas acting along (or even by air). In general, dimensional analysis insinuates that four transport properties
affect natural convection flows: density, isobaric specific heat capacity, dynamic viscosity and thermal conductivity. Simple
correlation equations of power form are useful to engineers for a quick estimate of the magnitudes of the space-mean heat
transfer coefficient. Detailed computations were made for four different gases: air, pure helium, pure argon, and a mixture
of pure helium and pure argon and the relative merits of each of them have been discussed. Five major cavities of relevance
in applications of thermal engineering have been analyzed in this work.
Received on 6 August 1999 相似文献
15.
V. M. Kuznetsov M. M. Kuznetsov 《Journal of Applied Mechanics and Technical Physics》1998,39(5):654-658
An analytical solution is obtained for the problem of acceleration of a body in a closed tube filled with a detonating mixture
of gases. It is assumed that the body enters the tube with a certain initial velocity sufficient for burning initiation in
an annular space between the body and tube surfaces. The effect of the mixture parameters, the shape and mass of the body,
and the integral dissipation of the total momentum and enthalpy of the flow on the finite values of the velocity and the acceleration
length is analyzed.
Central Aerohydrodynamic Institute, Zhukovskii 140160. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol.
39, No. 5, pp. 6–10, September–October, 1998. 相似文献
16.
Transformation of energy and composition of gas mixtures in a collision of rarefied supersonic flows
Transformation of energy and composition of gas mixtures in a convergent flow from a strip source on a cylindrical surface
toward the axis is systematically studied with the use of the direct simulation Monte Carlo method. Information on the influence
of gas-flow rarefaction and system geometry on the temperature and concentration of the heavy gas in a dense cloud formed
on the axis is obtained. The use of convergent supersonic flows is demonstrated to offer new possibilities for research in
the field of physical gas dynamics.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 198–204, March–April, 2009 相似文献
17.
The various oblique shock wave reflection patterns generated by a moving incident shock on a planar wedge using an ideal quantum
gas model are numerically studied using a novel high resolution quantum kinetic flux splitting scheme. With different incident
shock Mach numbers and wedge angles as flow parameters, four different types of reflection patterns, namely, the regular reflection,
simple Mach reflection, complex Mach reflection and the double Mach reflection as in the classical gas can be classified and
observed. Both Bose–Einstein and Fermi–Dirac gases are considered.
相似文献
18.
为了控制并预防原油的储存及输运过程中挥发气体造成的安全风险,在20 L球形爆炸容器内开展了由原油中挥发轻烃CH4、C3H8和C2H4构成的三元可燃混合气体的爆炸极限实验,提出并验证了基于Le Chatelier定律及Chemkin模拟的一维层流预混火焰模型预测三元可燃混合气体爆炸极限的方法。结果表明,三元可燃混合气体爆炸极限始终位于3种纯组分的爆炸极限内,随着某一纯组分增加呈现出接近其爆炸极限的趋势。3种纯组分对爆炸上限的影响要强于对爆炸下限的影响,其中C2H4对三元可燃混合气体爆炸上限影响尤为显著。两种预测方法的预测结果均与实验规律性一致。Le Chatelier定律预测混合气体爆炸下限较准确,但对爆炸上限的预测随着C2H4的增加偏差增大,修正后偏差明显减小;Chemkin预测爆炸下限虽存在一定偏差,但在实验偏差的允许范围内,可作为一种预测三元可燃混合气体爆炸下限的新方法。 相似文献
19.
A fluorescence image analysis procedure to determine the distribution of species concentration and density in a gas flow is
proposed. The fluorescent emission is due to the excitation of atoms/molecules of a gas that is intercepted by an electron
sheet. The intensity of the fluorescent light is proportional to the local number density of the gas. When the gas flow is
a mixture of different species, this proportionality can be used to extract the contribution associated with the species from
the spectral superposition acquired by a digital camera. In particular, the fact is exploited such that the ratio between
a pair of color intensities takes different values for different gases and that different linear superpositions of different
color intensities yield a ratio that varies with the species concentration. This leads to a method that simultaneously reveals
species concentrations and mass density of the mixture. For the proper working of a continuous electron gun in a gas, the
procedure can be applied to gas flow where the pressure is below the thresholds of 200∼300 Pa and the number density is no
greater than 1023 m−3. To maintain the constancy of the emission coefficients, the temperature variation in the flow should be inside the range
75–900 K (above the temperature where the probability to meet disequilibrium phenomena due to rarefaction is low, below the
temperature where visible thermal emission is present). The overall accuracy of the measurement method is approximately 10%.
The uncertainty can vary locally in the range from 5 to 15% for the concentration and from 5 to 20% for the density depending
on the local signal-to-noise ratio. The procedure is applied to two under-expanded sonic jets discharged into a different
gas ambient—Helium into Argon and Argon into Helium—to measure the concentration and density distribution along the jet axis
and across it. A comparison with experimental and numerical results obtained by other authors when observing under-expanded
jets at different Mach numbers is made with the density distribution along the axis of the jet. This density distribution
appears to be self-similar. 相似文献
20.
Yu. N. Gordeev A. E. Sandakov Yu. L. Chizhov 《Journal of Applied Mechanics and Technical Physics》2008,49(5):776-780
A problem of piston-induced displacement of one gas by another in cracks (porous media) in an axisymmetric case with a quadratic
drag law is studied. Self-similar solutions for determining the dynamic characteristics (velocity and pressure) of the displacing
and displaced gases are constructed in quadratures. The velocity and pressure are studied as functions of a self-similar variable
for several initial conditions and parameters.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 87–92, September–October, 2008. 相似文献