共查询到20条相似文献,搜索用时 15 毫秒
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The processes of dissolution and hydrate formation behind the front of a shock wave of moderate amplitude in water with carbon
dioxide bubbles are studied experimentally at various initial static pressures. The influence of a surface-active substance
(SAS) in the medium on the processes of dissolution and hydrate formation behind the shock wave is investigated. It is demonstrated
that behind a shock wave of moderate amplitude in a liquid with carbon dioxide bubbles an intensive process of dissolution
and hydrate formation takes place, resulting in complete disappearance of the gas phase in a matter of a few milliseconds.
The presence of an SAS in the medium does not significantly influence the processes of dissolution and hydrate formation within
the investigated periods of time. 相似文献
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A. V. Omel’chenko 《Technical Physics》2002,47(1):18-25
Relationships between the derivatives on both sides of a discontinuity in a nonstationary shock wave moving with acceleration in a one-dimensional vortex flow of perfect gas are deduced. The problem of interaction between the shock wave and a weak discontinuity is solved based on these relationships. 相似文献
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S. S. Anan’ev I. D. Bernal B. A. Demidov Yu. G. Kalinin V. A. Petrov 《Technical Physics》2010,55(5):703-708
The variation of the refractive index in polymethylmethacrylate (PMMA) behind the front of a shock wave excited by a high-current
electron beam is investigated. The values of refractive index in a pressure range of 2 and 4 GPa are determined from the deviation
of the diagnostic laser beam. The results are compared with the available data for shock compression of PMMA. 相似文献
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The variation of the temperature profile in a shock wave propagating in a vibrationally excited gas is studied as a function of the wave velocity and the degree of nonequilibrium of the gas. 相似文献
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K. A. Avdeev V. S. Aksenov A. A. Borisov D. G. Sevastopoleva R. R. Tukhvatullina S. M. Frolov F. S. Frolov I. O. Shamshin B. Basara W. Edelbauer K. Pachler 《Russian Journal of Physical Chemistry B, Focus on Physics》2017,11(2):261-271
The entry of a shock wave from air into water containing reactive gas (stoichiometric acetylene–oxygen mixture) bubbles uniformly distributed over the volume of the liquid has been numerically investigated using equations describing two-phase compressible viscous reactive flow. It has been demonstrated that a steady-state supersonic self-sustaining reaction front with rapid and complete fuel burnout in the leading shock wave can propagate in this bubbly medium. This reaction front can be treated as a detonation-like front or “bubble detonation.” The calculated and measured velocities of the bubble detonation wave have been compared at initial gas volume fraction of 2 to 6%. The observed and calculated data are in satisfactory qualitative and quantitative agreement. The structure of the bubble detonation wave has been numerically studied. In this wave, the gas volume fraction behind the leading front is approximately 3–4 times higher than in the pressure wave that propagates in water with air bubbles when the other initial conditions are the same. The bubble detonation wave can form after the penetration of the shock wave to a small depth (~300 mm) into the column of the bubbly medium. The model suggested here can be used to find optimum conditions for maximizing the efficiency of momentum transfer from the pressure wave to the bubbly medium in promising hydrojet pulse detonation engines. 相似文献
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The structure of a shock wave propagating in a plasma with two types of ions has been studied within the model of multifluid hydrodynamics based on the 13-moment system of Grad’s equations. Although the averaged dynamics of the shock front coincides with the single-component variant of the average-ion model, its structure is different at a noticeable difference between charge-to-mass ratios of different ions, demonstrating their separation on the shock front. For the problem of inertial confinement fusion, the range of parameters for which such a separation is important, as well as physical processes determining the two-component structure of the shock front, has been established. 相似文献
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Stationary normal shock waves in a hard-core fluid were simulated via molecular dynamics. Profiles of various physical quantities near the shock front were calculated, and their dependence on the fluid density and the shock Mach number was studied. 相似文献
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《中国物理 B》2015,(9)
The combustion of magnesium particles in water vapor is of interest for underwater propulsion and hydrogen production. In this work, the combustion process of a single magnesium particle in water vapor is studied both experimentally and theoretically. Combustion experiments are conducted in a combustor filled with motionless water vapor. Condensation of gas-phase magnesia on the particle surface is confirmed and gas-phase combustion flame characteristics are observed. With the help of an optical filter and a neutral optical attenuator, flame structures are captured and determined. Flame temperature profiles are measured by an infrared thermometer. Combustion residue is a porous oxide shell of disordered magnesia crystal, which may impose a certain influence on the diffusivity of gas phases. A simplified one-dimensional, spherically symmetric, quasi-steady combustion model is then developed. In this model, the condensation of gas-phase magnesia on the particle surface and its influence on the combustion process are included, and the Stefan problem on the particle surface is also taken into consideration. With the combustion model, the parameters of flame temperature, flame diameter, and the burning time of the particle are solved analytically under the experimental conditions. A reasonable agreement between the experimental and modeling results is demonstrated, and several features to improve the model are identified. 相似文献
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Summary Similarity solutions of the propagation of cylindrical blast waves through a self-gravitating polytropic gas caused by an
instantaneous release of finite energy are investigated theoretically including the influence of transverse magnetic field.
A comparative study of the distributions of velocity, density, mass, pressure, temperature and magnetic field has been illustrated
through figures.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
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The propagation of shock waves in He and Ar containing 0.01% of molybdenum hexacarbonyl Mo(CO)6 as a heavy component of the mixture has been investigated with the use of the method of multichannel emission spectroscopy and an electrostatic probe with a spatial resolution of 0.2 mm placed in the core of a flow. The measurements have been carried out in incident shock waves with a high-vacuum shock tube in a Mach number range of 2.5–3.4. The equilibrium parameters behind the shock front are P 2 = 0.109–1.124 atm and T 2 = 853–1280 K, the concentration of Mo(CO)6 is specially controlled, and high-purity He and Ar are used. The experiments are carried out under conditions when collisions between heavy molecules can be disregarded. It has been found that a narrow conduction band with a carrier density of more than 105 cm?3 appears in the shock front. The carrier density and its time characteristics have been measured. A correlation has been found between the conduction band and peaks of the nonequilibrium radiation in the visible and ultraviolet spectral ranges. This radiation disappears when the equilibrium parameters are reached behind the shock wave. The arrival of the conduction band and radiation band in the shock front at the measurement section advances the arrival of the density gradient of the shock front in most regimes. It has been found that the maximum conduction increases as the square of the Mo(CO)6 concentration and decreases with increasing pressure. The effective threshold of the appearance of charges in the shock front has been determined as 1.35 ± 0.15 eV. A qualitative mechanism of the effect has been proposed with allowance for possible separation of charges in the shock front and with the inclusion of the “hot” wing of the energy distribution function of pair collisions. 相似文献
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Within an ultrasonic standing wave particles experience acoustic radiation forces causing agglomeration at the nodal planes of the wave. The technique can be used to agglomerate, suspend, or manipulate particles within a flow. To control agglomeration rate it is important to balance forces on the particles and, in the case where a fluid/particle mix flows across the applied acoustic field, it is also necessary to optimise fluid flow rate. To investigate the acoustic and fluid forces in such a system a particle model has been developed, extending an earlier model used to characterise the 1-dimensional field in a layered resonator. In order to simulate fluid drag forces, CFD software has been used to determine the velocity profile of the fluid/particle mix passing through the acoustic device. The profile is then incorporated into a MATLAB model. Based on particle force components, a numerical approach has been used to determine particle paths. Using particle coordinates, both particle concentration across the fluid channel and concentration through multiple outlets are calculated. Such an approach has been used to analyse the operation of a microfluidic flow-through separator, which uses a half wavelength standing wave across the main channel of the device. This causes particles to converge near the axial plane of the channel, delivering high and low particle concentrated flow through two outlets, respectively. By extending the model to analyse particle separation over a frequency range, it is possible to identify the resonant frequencies of the device and associated separation performance. This approach will also be used to improve the geometric design of the microengineered fluid channels, where the particle model can determine the limiting fluid flow rate for separation to occur, the value of which is then applied to a CFD model of the device geometry. 相似文献
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A. Emelianov A. Makeich H.Gg. Wagner C. Schulz 《Proceedings of the Combustion Institute》2007,31(1):649-656
The process of heat release during carbon particle formation and growth after pyrolysis of carbon suboxide C3O2 behind shock waves was investigated. For this goal, temperature and optical density of gas-particle mixtures initially consisting of 3% C3O2 + 5% CO2 in Ar were measured as a function of time. The temperature was determined by two-channel emission-absorption spectroscopy at λ = 2.7 ± 0.4 μm, corresponding to the CO2 (1,0,1) vibrational band. In the range of initial temperatures behind the shock waves from 1600 up to 2200 K a significant heating of the mixture during particle formation and growth was observed that increased towards higher temperatures. The analysis of the obtained data in combination with previous results about the temperature dependence of the particle size shows a decrease of the heat release of condensation from ∼200 kJ/mol per atom for particles containing ∼1000 atoms to ∼50 kJ/mol per atom for particle containing ∼106 atoms. 相似文献