Diffusion and Convective Instability in Ternary Gas Mixture

2013 ◽  
Vol 378 ◽  
pp. 253-258
Author(s):  
Vladimir Kossov ◽  
Yuriy Zhavrin ◽  
Olga Fedorenko
Keyword(s):  
Finite Size ◽  
Gas Mixture ◽  
Governing Equations ◽  
Shadow Method ◽  
Diffusion Channel ◽  
Convective Flows ◽  
Series Of Experiments ◽  
The Stability ◽  
Stability Limits ◽  
Good Agreement

The main objective of this article is to investigate the evolution of the mass transfer regimes in three-component gas mixture subject to the pressure and the diameter of diffusion channel. Two series of experiments on gaseous diffusion instabilities are reported. In one series the stability limits are investigated as a function of pressure and diameter for the system 0.4722 He + 0.5278 Ar - N2. In the other series the convection structures are made visible with the help of shadow method. The experimentalresults reveal that an increase in the pressure and the diameter of diffusion channel leads to a change of the type of mixing in ternary gas mixture.Numerical analysis of the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter through the walls of diffusion channel. Through the Rayleigh partial numbers, the influences of the pressure and the diameter of diffusion channel on the behaviour of diffusion and convective flows are examined. The present results are in good agreement with the experimental data.

scholarly journals NUMERICAL RESEARCH OF THE CHANGE OF REGIME FOR UNSTABLE MASS TRANSFER IN A TERNARY GAS MIXTURE HYDROGEN- NITRIC OXIDE-NITROGEN

2020 ◽  
Vol 72 (4) ◽  
pp. 112-116
Author(s):  
A.B. Kalimov ◽  
◽  
O.V. Fedorenko ◽  
V.N. Kossov ◽  
◽  
...  
Keyword(s):  
Mass Transfer ◽  
Finite Size ◽  
Pressure Change ◽  
Gas Mixture ◽  
Governing Equations ◽  
Diffusion Channel ◽  
Numerical Research ◽  
Pressure Changes ◽  
Matter Transfer ◽  
Good Agreement

On the basis of the software package "MathCad", by solving the Stefan-Maxwell diffusion equations, the evolution of the features of mass transfer in a three-component gas mixture, depending on pressure changes, has been numerically studied. In this analysis, the mixing process is studied in a vertical cylindrical channel of a finite size and at the isothermal conditions. The governing equations are solved at the boundary conditions assuming the absence of matter transfer through the walls of diffusion channel. Through the Rayleigh partial numbers, the influence of the pressure change on the behaviour of diffusion and convective flows is examined. The numerical results reveal that an increase in the pressure leads to a change of modes in ternary gas mixture. The present results are in good agreement with the existing experimental data.

scholarly journals On the stability for three-dimensional disturbances of viscous fluid flow between parallel walls

1933 ◽  
Vol 142 (847) ◽  
pp. 621-628 ◽  
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Finite Size ◽  
Critical Value ◽  
The Stability ◽  
The One ◽  
Von Mises ◽  
Shearing Motion ◽  
Determining Factor ◽  
Good Agreement

The turbulence problem is still unsolved, through a number of valuable papers have been published on it comparatively recently. But, since Hopf and von Mises proved that uniform shearing motion between two parallel planes was stable for infinitesimal disturbances but unstable for disturbances of a finite size has become more and more widely held. Von mises suggested that the reoughness of the walls might be the determining factor, but the experiments of Schiller have shown that the degree of roughness of the walls is of negligible influence on the critical value of Reynold's number. He concluded that the breakdown of laminar flow depended primarily on the size of the initial disturbance, in agreement eith Osborne Reynold's view. Important papers have been published by Noether and Tollmien, whose conclusions are in contradiction to one another. On the one hand, Noether, by a formal investigation of the asymptotic solutions of the equation governing the two-dimensional disturbances of flow between parallel walls, claims to have proved that all velocity profiles are stable for all values of Reynolds' number. On the other hand, Tollmien has determined a critical value of Reynolds' number for the flow past a flat plate placed edgeways to the stream. This value is in good agreement with the experimental results. There are, however, certain points in his analysis which are not clear and it would be useful to know if the method gave results in agreement with those derived more strictly.

scholarly journals Влияние угла наклона канала на конвективное смешение, вызванное неустойчивостью механического равновесия тройной газовой смеси при изотермической диффузии

2019 ◽  
Vol 45 (21) ◽  
pp. 7
Author(s):  
М.К. Асембаева ◽  
В.Н. Косов ◽  
С.А. Красиков ◽  
О.В. Федоренко
Keyword(s):  
Slope Angle ◽  
Nonlinear Dependence ◽  
Gas Mixture ◽  
Mixing Rate ◽  
Nitrogen Gas ◽  
Diffusion Channel ◽  
Convective Flows ◽  
Elevated Pressures ◽  
Isothermal Diffusion ◽  
Partial Transfer

The features of the convective regime that arose due to the instability of mechanical equilibrium of the ternary helium – argon – nitrogen gas mixture during isothermal diffusion were experimentally studied. The influence of the slope angle of the diffusion channel on the intensity of convective flows is considered. The intensity of partial transfer of components in the inclined channel at elevated pressures was measured. A nonlinear dependence of the mixing rate of the components on the angle of inclination was found. It has been established that the observed transfer of components, which is atypical for diffusion, is possible with a certain composition of the gas mixture.

On the stability of Kelvin waves

1989 ◽  
Vol 206 ◽  
pp. 1-23 ◽  
Author(s):  
W. K. Melville ◽  
G. G. Tomasson ◽  
D. P. Renouard
Keyword(s):  
Numerical Solutions ◽  
Nonlinear Resonance ◽  
Approximate Solutions ◽  
Kelvin Waves ◽  
Kelvin Wave ◽  
Governing Equations ◽  
Weakly Nonlinear ◽  
Approximate Analytical Solutions ◽  
The Stability ◽  
Good Agreement

We consider the evolution of weakly nonlinear dispersive long waves in a rotating channel. The governing equations are derived and approximate solutions obtained for the initial data corresponding to a Kelvin wave. In consequence of the small nonlinear speed correction it is shown that weakly nonlinear Kelvin waves are unstable to a direct nonlinear resonance with the linear Poincaré modes of the channel. Numerical solutions of the governing equations are computed and found to give good agreement with the approximate analytical solutions. It is shown that the curvature of the wavefront and the decay of the leading wave amplitude along the channel are attributable to the Poincaré waves generated by the resonance. These results appear to give a qualitative explanation of the experimental results of Maxworthy (1983), and Renouard, Chabert d'Hières & Zhang (1987).

On the stability of the Stewartson layer

1976 ◽  
Vol 76 (2) ◽  
pp. 289-306 ◽  
Author(s):  
Kiyoshi Hashimoto
Keyword(s):  
Boundary Layer ◽  
Growth Rate ◽  
Incompressible Fluid ◽  
Layer Structure ◽  
Rossby Number ◽  
Governing Equations ◽  
Azimuthal Component ◽  
Ekman Number ◽  
The Stability ◽  
Good Agreement

The stability of the Stewartson layer in a rotating incompressible fluid is investigated within the framework of a linear theory. The boundary-layer structure of the shear layer is correctly taken into account and the effect of viscous dissipation on the disturbance is included in the governing equations. The growth rate ωi of the disturbance is given as a function of the unified parameter mRo/(γ½), where m, an integer, is the azimuthal component of the wavenumber vector, γ the radius of the layer, Ro the Rossby number and E the Ekman number. Instability occurs when m Ro/(γ½) > 9·5. The time evolution of a growing disturbance is given schematically. Comparison of our results with the experiments by Hide & Titman shows good agreement.

Closed Form Solutions for Electrostatically Actuated Micromirrors Considering the Bending Effect

2011 ◽  
Author(s):  
Hamid Moeenfard ◽  
Mohammad Taghi Ahmadian ◽  
Hosein Moeenfard
Keyword(s):  
Equilibrium Equations ◽  
Closed Form Solutions ◽  
Electrostatically Actuated ◽  
Bending Effect ◽  
Displacement Behavior ◽  
Micro Actuators ◽  
The Stability ◽  
Experimental Findings ◽  
Stability Limits ◽  
Good Agreement

In the current paper, analytical solutions are presented for the nonlinear problem of electrostatically actuated torsional micromirrors considering the bending of the torsional beams. Energy method is used for finding the equilibrium equations. Then the explicit function theorem is utilized for finding the equations governing the instability mode of the mirror. The presented results show that neglecting the bending effect in electrostatic torsion micro actuators can cause to several hundred percent of overestimation of the stability limits of the device. In order to study the voltage-angle and voltage-displacement behavior of the micromirror, equilibrium equations are solved using HPM. Presented results are in good agreement with numerical simulations and experimental findings.

Stability as a constraint in sagittal plane human force exertion modeling

1998 ◽  
Vol 1 (1) ◽  
pp. 23-39
Author(s):  
Carter J. Kerk ◽  
Don B. Chaffin ◽  
W. Monroe Keyserling
Keyword(s):  
Muscle Strength ◽  
Ankle Joint ◽  
Coefficient Of Friction ◽  
Sagittal Plane ◽  
Biomechanical Model ◽  
Whole Body ◽  
The Stability ◽  
Joint Center ◽  
Static Conditions ◽  
Stability Limits

The stability constraints of a two-dimensional static human force exertion capability model (2DHFEC) were evaluated with subjects of varying anthropometry and strength capabilities performing manual exertions. The biomechanical model comprehensively estimated human force exertion capability under sagittally symmetric static conditions using constraints from three classes: stability, joint muscle strength, and coefficient of friction. Experimental results showed the concept of stability must be considered with joint muscle strength capability and coefficient of friction in predicting hand force exertion capability. Information was gained concerning foot modeling parameters as they affect whole-body stability. Findings indicated that stability limits should be placed approximately 37 % the ankle joint center to the posterior-most point of the foot and 130 % the distance from the ankle joint center to the maximal medial protuberance (the ball of the foot). 2DHFEC provided improvements over existing models, especially where horizontal push/pull forces create balance concerns.

scholarly journals A NEW APPROACH TO DYNAMIC FINITE-SIZE SCALING

2003 ◽  
Vol 14 (07) ◽  
pp. 945-954 ◽  
Author(s):  
MEHMET DİLAVER ◽  
SEMRA GÜNDÜÇ ◽  
MERAL AYDIN ◽  
YİĞİT GÜNDÜÇ
Keyword(s):  
Three Dimensional ◽  
Finite Size ◽  
Taylor Series Expansion ◽  
Scaling Behavior ◽  
Dynamic Scaling ◽  
Finite Size Scaling ◽  
New Approach ◽  
Size Scaling ◽  
Dynamic Exponent ◽  
Good Agreement

In this work we have considered the Taylor series expansion of the dynamic scaling relation of the magnetization with respect to small initial magnetization values in order to study the dynamic scaling behavior of two- and three-dimensional Ising models. We have used the literature values of the critical exponents and of the new dynamic exponent x0 to observe the dynamic finite-size scaling behavior of the time evolution of the magnetization during early stages of the Monte Carlo simulation. For the three-dimensional Ising model we have also presented that this method opens the possibility of calculating z and x0 separately. Our results show good agreement with the literature values. Measurements done on lattices with different sizes seem to give very good scaling.

OPTIMAL VELOCITY MODEL WITH RELATIVE VELOCITY

2006 ◽  
Vol 17 (01) ◽  
pp. 65-73 ◽  
Author(s):  
SHIRO SAWADA
Keyword(s):  
Nonlinear Analysis ◽  
Relative Velocity ◽  
Velocity Model ◽  
Fundamental Diagram ◽  
Optimal Velocity ◽  
Traffic Jam ◽  
Optimal Velocity Model ◽  
Linear And Nonlinear ◽  
The Stability ◽  
Good Agreement

The optimal velocity model which depends not only on the headway but also on the relative velocity is analyzed in detail. We investigate the effect of considering the relative velocity based on the linear and nonlinear analysis of the model. The linear stability analysis shows that the improvement in the stability of the traffic flow is obtained by taking into account the relative velocity. From the nonlinear analysis, the relative velocity dependence of the propagating kink solution for traffic jam is obtained. The relation between the headway and the velocity and the fundamental diagram are examined by numerical simulation. We find that the results by the linear and nonlinear analysis of the model are in good agreement with the numerical results.

Global Stability Analysis of the Wake behind a Circular Cylinder Based on the POD-Chiba Method

2011 ◽  
Vol 137 ◽  
pp. 72-76
Author(s):  
Wei Zhang ◽  
Xian Wen ◽  
Yan Qun Jiang
Keyword(s):  
Stability Analysis ◽  
Circular Cylinder ◽  
Global Stability ◽  
Dimensional Model ◽  
Global Stability Analysis ◽  
The Stability ◽  
Low Dimensional ◽  
Proper Orthogonal ◽  
Calculated Amount ◽  
Good Agreement

A proper orthogonal decomposition (POD) method is applied to study the global stability analysis for flow past a stationary circular cylinder. The flow database at Re=100 is obtained by CFD software, i.e. FLUENT, with which POD bases are constructed by a snapshot method. Based on the POD bases, a low-dimensional model is established for solving the two-dimensional incompressible NS equations. The stability of the flow solution is evaluated by a POD-Chiba method in the way of the eigensystem analysis for the velocity disturbance. The linear stability analysis shows that the first Hopf bifurcation takes place at Re=46.9, which is in good agreement with available results by other high-order accurate stability analysis methods. However, the calculated amount of POD is little, which shows the availability and advantage of the POD method.

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