Effects of surface dispersion forces on the flow of a low-density gas in a thin capillary

The paper discusses the flow of a low-density gas in a thin circular capillary with allowance for the dispersion interactions of the gas molecules with the capillary walls. The gas flow rate at the exit is determined. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 53–56, March, 1998.     

Dynamics of airflow in a short inhalation

During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickly. The consequences for flow development and convective transport of an inhaled gas were investigated in a subject geometry extending from the nose to the bronchi. The progress of flow transition and the advance of an inhaled non-absorbed gas were determined using highly resolved simulations of a sniff 0.5 s long, 1 l s⁻¹ peak flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved through three phases: (i) an initial transient of about 50 ms, roughly the filling time for a nasal volume, (ii) quasi-equilibrium over the majority of the inhalation, and (iii) a terminating phase. Flow transition commenced in the supraglottic region within 20 ms, resulting in large-amplitude fluctuations persisting throughout the inhalation; in the nose, fluctuations that arose nearer peak flow were of much reduced intensity and diminished in the flow decay phase. Measures of gas concentration showed non-uniform build-up and wash-out of the inhaled gas in the nose. At the carina, the form of the temporal concentration profile reflected both shear dispersion and airway filling defects owing to recirculation regions.     

Experimental determination of the energy of a gas vortex motion during autooscillations in a free convective flow

Free convective gas flow in a “singing” flame and in a Rijke tube was studied in the case of small Reynolds numbers (Re < 1000). A method for determining the dissipated gas flow energy is proposed, which is based on the measurement of displacements of a resonator tube from the position of mechanical equilibrium upon a change from stationary to autooscillatory flow regime, which is accompanied by the spontaneous formation of vortex structures. It is shown that the vortex motion in the gas leads to a decrease in thermal flux in the tube cross section. The energy of rotational motion as a function of the heat-source power exhibits a hysteresis behavior.     

Visualization of oscillating flow in a double-inlet pulse tube refrigerator with a diaphragm inserted in a bypass-tube

The double-inlet pulse tube refrigerator that has a diaphragm inserted in a bypass-tube, which enabled it to transmit a pressure oscillation whereas to obstruct a DC gas flow, was manufactured and tested. The oscillating flow behavior inside of the refrigerator was studied by using a smoke-wire flow visualization technique. It was found that if the diaphragm was optimized, the performance would be improved more than that of the refrigerator with a bypass valve due to the increase in the P–V work of the gas and the decrease in the convective heat loss caused by a secondary flow.     

Measurement of conductance of a sapphire sealed variable leak valve

A variable leak valve (VLV) is used to a great extend to regulate throughput of process gases into the vacuum system. A gas flow through the VLV can be in different flow regimes: viscous, transition or molecular, depending on the upstream gas pressure. In this work the pressure dependence of conductance of a sapphire sealed VLV has been investigated.The conductance of the VLV was determined by measuring gas flow in known volume using the pressure rise method. The pressure rise was measured using a spinning rotor gauge while the upstream pressure was measured by capacitance diaphragm gauges. The VLV conductance was determined with a relative standard uncertainty of 1.2%.The measurements of conductance were done for different VLV settings. To reduce the influence of outgassing on the gas flow measurement by the pressure rise method we have used a non-evaporable getter in the measurement volume. Argon was used as the test gas. As a result, the throughput of VLV for Ar could be measured down to 5 × 10⁻¹¹ Pa m³ s⁻¹. The time stability of the VLV for conductance set at 5 × 10⁻¹⁰ l s⁻¹ and fill pressures of Ar ranging from 0.2 kPa to 5 kPa was also determined.     

Stability and form of an arc column in a transverse gas flow

The analytic conditions for stable burning of an electric arc in a gas flow are obtained. The form of the arc column in a transverse gas flow is determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 4, pp. 650–654, October, 1986.     

Reaction field analysis of a non-thermal plasma flowing in a rectangular reactor

Chemical reactive fields of non-thermal plasma flowing were clarified by using both experimental and numerical methods in the present study. The plasma was generated by using needle-plate electrodes with applied voltage of 12 kV and a square wave of 20 Hz. The operating gas was air injected at a rate of 1-10 Sl/min through a rectangular reactor with a 3×7 mm cross section. Distributions of gas velocity, gas temperature and NO concentration were clarified by experimental and numerical methods. The NO concentration was strongly influenced by the gas flow rate, because the N concentration was rapidly decreased in the case of small gas flow rate.     

Turbulent flow of a chemically reactive gas suspension in a channel with a blow

The influence of the chemical reactions occurring in the gas phase of a gas suspension flowing in a channel with penetrable walls and the combustion of the condensed-impurity particles in this flow on its gasdynamic structure has been investigated. It is shown that the order of the system of equations defining a flow of a chemically reactive gas suspension with a homogeneous exothermic reaction proceeding at a definite rate and a heterogeneous combustion of the condensed-phase particles can be decreased if certain assumptions are mode. The distributions of the parameters of the gas and dispersed phases were calculated as functions of the rate of blow and the sizes of the particles. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 91–98, July–August, 2007.     

Magnetic field control of a supersonic nitrogen flow

Magnetohydrodynamic impact on a cold supersonic nitrogen flow with external magnetic field was realized in an experimental complex based on the Big Shock Tube at the Ioffe Physicotechnical Institute. A pulsed supersonic flow with a Mach number of M=4 and steady phase duration of about 1.5 ms was created by expansion of the shock-heated nitrogen flow from a supersonic nozzle. The gas was ionized by pulsed discharge between two electrodes mounted on the nozzle wall so that an electric current of up to ∼500 A passed in the direction perpendicular to the gas flow at the dielectric wall. External magnetic field ∼0.3 T was perpendicular to the gas flow and the current direction. It is established that the magnetic field significantly modifies the shock wave structure in the flow.     

Calculation of the probability of passage of gas particles through a circular channel with absorbing walls

We consider the mass transport of a gas subject to free-molecular flow in a circular channel with absorbing walls. An analytical expression for the gas flow rate is obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 4, pp. 580–584, April, 1987.     

The effect of particles on the gas velocity in a free turbulent flow

The article describes experimental studies carrid out to investigate the interaction between gas and particles in a free turbulent two-phase flow at the outlet from a rather long vertical tube.Notation A cross-sectional area of the flow - A ₀ initial cross-sectional area of the flow - d diameter of the flow - d _p average diameter of particles - I _i initial momentum of the two-phase flow - k mass ratio of particles and gas (k=m _p/m _g) - k ₀ mass ratio of particles and gas in the initial cross-section of the two-phase flow (x=0) - m _g mass flow rate of gas - m _p mass flow rate of particles - r instantaneous radius of the flow - r ₀ radius of the initial cross-section of the flow - r _1/2 normal distance from the flow axis to the point at which the velocity of gas is equal to the half of the axial velocity - R cross-sectional radius of the flow - u velocity - u _a air velocity - u _fa gas velocity on the flow axis - u _g gas velocity - u _av average gas velocity in the initial cross-section for two-phase and single-phase flows - u ₀ gas velocity on the axis of the initial cross-section of the flow - u _p particle velocity - x distance along the axis from the original of coordinates - _g gas density Institute of Nuclear Research Vina, Laboratory of Thermal and Power Engineering, Belgrade, Yugoslavia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 3, pp. 361–365, May–June, 1995.     

The Initial Equations and the Equations for Measuring the Mass and Volume Flow Rates of a Gas

A mathematical model of the flow of a gas in Laval nozzles is analyzed. The model is used to obtain equations for measuring the mass and volume flow rates of a gas.__________Translated from Izmeritel’naya Tekhnika, No. 4, pp. 44–48, April, 2005.     

Isothermal slip of a binary gas mixture along a solid surface

This paper investigates Couette flow of a binary mixture of a rarefied gas between two flat plates. An analytical expression for the rate of isothermal slip of a binary mixture of the rarefied gas along the surface is obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 4, pp. 683–686, April, 1977.     

Velocity Fluctuations in a Particle-Laden Turbulent Flow over a Backward-Facing Step

Dilute gas-particle turbulent flow over a backward-facing step is numerically simulated. Large Eddy Simulation (LES) is used for the continuous phase and a Lagrangian trajectory method is adopted for the particle phase. Four typical locations in the flow field are chosen to investigate the two-phase velocity fluctuations. Time-series velocities of the gas phase with particles of different sizes are obtained. Velocity of the small particles is found to be similar to that of the gas phase, while high frequency noise exists in the velocity of the large particles. While the mean and rms velocities of the gas phase and small particles are correlated, the rms velocities of large particles have no correlation with the gas phase. The frequency spectrum of the velocity of the gas phase and the small particle phase show the -5/3 decay for higher wave number, as expected in a turbulent flow. However, there is a "rising tail' in the high frequency end of the spectrum for larger particles. It is shown that large particles behave differently in the flow field, while small particles behave similarly and dominated by the local gas phase flow.     

Stabilization of temperature and pressure of a real gas in a stopped pipe

Nonisothermal unsteady flow of a real gas in a pipe is studied. A numerical method is given for solving a system of quasi-linear differential equations that describe the flow of a real gas in a stopped pipe. The calculated results are discussed.     

Gas flow through a porous heat-releasing medium with allowance for the temperature dependence of gas viscosity

The gas flow through a porous heat-releasing medium is considered. It has been noted that account for the temperature dependence of the gas viscosity strongly influences the solution: the gas flow rate markedly decreases and a stronger heating occurs. Analysis of the flow of a gas with a temperature-dependent viscosity by the Sutherland formula has revealed two steady-state cooling regimes — stable and unstable ones. It has been shown that the possibility of the steady-state regime is determined not only by the problem parameters but by the initial conditions as well. The transient process from the state of rest in the absence of heat release to the state of the regime of induced filtration upon instantaneous switching-on of heat input is described. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 35–40, January–February, 2006.     

Effect of eddy formation on gas mixture homogeneity near a substrate in a vertical reactor for CdHgTe deposition

This paper presents simulation results obtained for an unsteady-state flow of a multicomponent gas mixture in a flow-type vertical reactor using a three-dimensional mathematical model that takes into account the convective mass and heat transport, compressibility, viscosity, and thermal conductivity of the components and gas flow turbulization. We identify the gas dynamic mechanism behind eddy formation in the reactor and examine the influence of the viscosity, density, and speed of the flow components on eddy formation and the homogeneity of the gas mixture over the substrate.     

Theoretical model of nonequilibrium of extraction of a gas dissolved in a fluid during pressure fluctuations in a flow

An engineering model and a method of computing nonequilibrium extraction of a gas dissolved in a fluid during pressure fluctuations in a dispersely-nucleate gas-liquid flow that differs from a known flow by taking account of the turbulent nature of the relative phase motion and a more accurate determination of the gas bubble radius in an equivalent flow. The results of computing the magnitude of the additional gas-extraction during pressure fluctuations in a pipeline are compared with experimental data obtained earlier in water and carbon dioxide that verifies the reliability of the developed theoretical model.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 4, pp. 655–659, October, 1990.     

Hydrodynamics of a spouting bed with an active near-wall zone

Results of experimental studies of the bed porosity, gas velocity, time of residence, and intensity of agitation in a spouting bed with peripheral admission of the gas are presented. In particular, it is shown that a change in the ratio of the lower and peripheral flow rates of the gas allows one to control the bed structure. The effect of a twist of the lower gas flow on the porosity of the bed is analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 296–301, March–April, 2000.