Experimental methods for recording the process of diffusion instability in gas systems

DOI: 10.34759/trd-2023-128-09


Poyarkov I. V., Lipatova L. I.*

Moscow State University of Civil Engineering, MSUCE, 26, Yaroslavskoe shosse, Moscow, 129337, Russia

*e-mail: physics.801.lli@mail.ru


The article provides an overview of experimental methods for gas mixture registering the transition from a stable diffusion mode to a state of diffusion instability while mixing process.

Experiments on mixing process registration of gas systems by the shadowgrams method are described. This method allows observing the mixing process dynamics, determining visually the boundary of the mode change during the mass transfer process, as well as obtaining qualitative information on the spatial non-uniformities distribution and the nature of their behavior throughout the unstable mixing process. The catarometric method allows recording the mixing process dynamics, starting from the irregular fluctuations in the total concentration and ending with a steady convective process. The article provides the description of quantitative methods for determining the system thermodynamic parameters, at which diffusion instability occurs. The method for thermodynamic parameters determining with respect to the partial flows of the mixture components allows accurate computing of the stable diffusion boundary, and the method of criteria numbers application allows obtaining the value of the critical number of convective stability for a multicomponent gas mixture under isothermal conditions in the gravity field. The pros and contras of employing the methods in the article while the system parameters determining, at which transition from the diffusion region to the region of unstable diffusion occurs, are analyzed.

It is noted that experimental methods — the tenegram method and the catarometric method — allow us to observe the nature of the mixing process, while quantitative methods — the method of determining thermodynamic parameters with respect to the partial flows of the mixture components and the method of using criterion numbers — allow us to find the conditions under which it changes.


mass transfer; mixing mode; diffusion instability; convection; shadowgram method, catarometric method


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