Oscillatory and monotonic instability at the boundary of the transition ‘molecular diffusion-concentration convection’ in ternary gas mixtures

2000 ◽  
Vol 73 (2) ◽  
pp. 303-310 ◽  
Author(s):  
V. N. Kosov ◽  
V. D. Seleznev ◽  
Yu. I. Zhavrin
Keyword(s):  
Molecular Diffusion ◽  
Gas Mixtures ◽  
Monotonic Instability ◽  
Concentration Convection

scholarly journals Numerical Investigation into the Flow Characteristics of Gas Mixtures in Knudsen Pump with Variable Soft Sphere Model

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 784
Author(s):  
Chunlin Du ◽  
Xiaowei Wang ◽  
Feng Han ◽  
Xiaoyu Ren ◽  
Zhijun Zhang
Keyword(s):  
Flow Pattern ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Molecular Diffusion ◽  
Flow Characteristics ◽  
Gas Mixtures ◽  
Soft Sphere ◽  
Knudsen Pump

In Knudsen pumps with geometric configuration of rectangle, gas flows are induced by temperature gradients along channel walls. In this paper, the direct simulation Monte Carlo (DSMC) method is used to investigate numerically the flow characteristics of H2–N2 mixtures in the Knudsen pump. The variable soft sphere (VSS) model is applied to depict molecular diffusion in the gas mixtures, and the results obtained are compared with those calculated from a variable hard sphere (VHS) model. It is demonstrated that pressure is crucial to affecting the variation of gas flow pattern, but the gas concentration in H2–N2 mixtures and the collision model do not change the flow pattern significantly. On the other hand, the velocity of H2 is larger than that of N2. The velocities of H2 and N2 increase if the concentration of H2 rises in the gas mixtures. The results of velocity and mass flow rate obtained from VSS and VHS models are different. Finally, a linear relation between the decrease of mass flow rate and the increase of H2 concentration is proposed to predict the mass flow rate in H2–N2 mixtures.

scholarly journals FEATURES OF ISOTHERMAL MULTICOMPONENT MIXING OF GAS MIXTURES CONTAINING METHANES AT CONVECTIVE INSTABILITY

2020 ◽  
Vol 71 (3) ◽  
pp. 118-122
Author(s):  
V.N. Kossov ◽  
◽  
V. Mukamedenkyzy ◽  
А. Zhussanbayeva ◽  
◽  
...  
Keyword(s):  
Convective Instability ◽  
Vertical Channel ◽  
Initial Mixture ◽  
Gas Mixtures ◽  
Convective Mixing ◽  
Boundary Relation ◽  
Concentration Convection ◽  
Calculation Results ◽  
The Difference ◽  
Rayleigh Numbers

The features of the change in the regimes "diffusion-gravitational concentration convection" in isothermal ternary gas mixtures have been studied experimentally and numerically. It is shown that, at a certain pressure, due to the difference in the diffusion coefficients of the components, an instability of mechanical equilibrium arises, leading to the appearance of structured convective formations. Calculation results are compared with experimental data on the location of the instability boundaries in the studied gas mixtures. Intensity of convective mixing is also influenced by the content of the component with the highest molecular weight in the initial mixture. In terms of Rayleigh numbers, a boundary relation is obtained that determines the regime change. The solution of the problem of multicomponent mixing in a cylindrical vertical channel of finite height with solid and impermeable boundaries for the substance made it possible to determine the concentration distribution along the length.

PLASMA SPRAYING OF BORON CARBIDE USING TERNARY GAS MIXTURES

2010 ◽  
Vol 14 (4) ◽  
pp. 379-388
Author(s):  
S. Janisson ◽  
Armelle Vardelle ◽  
Michel Vardelle ◽  
Pierre Fauchais ◽  
E. Meillot
Keyword(s):  
Boron Carbide ◽  
Plasma Spraying ◽  
Gas Mixtures
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