Numerical simulation of complex gas flows in concentrated fire vortices

About the authors:

Sergei P. Bautin, Dr. Sci. (Phys.-Math), Professor, Department of Higher and Applied Mathematics, Snezhinsk Physical-Technical Institute, National Research Nuclear University MEPhI (Snezhinsk); eLibrary AuthorID, sbautin@usurt.ru

Alexandr G. Obukhov, Dr. Sci. (Phys.-Math), Professor, Department of Business Informatics and Mathematics, Industrial University of Tyumen; eLibrary AuthorID, agobukhov@inbox.ru

Abstract:

This article presents the results of numerical simulation of free fire vortices arising in laboratory conditions. The authors demonstrate the possibility of obtaining such concentrated fire vortices in a series of experimental studies conducted under the supervision of A.  Yu.  Varaksin, a corresponding member of the Russian Academy of Sciences, at the Joint Institute for High Temperatures of the Russian Academy of Sciences.

The authors propose to consider the analytical and numerical studies of arising complex swirling gas flows during local heating of a metal underlying surface by several sources from the point of view of gas dynamics. When considering complex flows of a heating gas as a motion of a viscous, heat-conducting, and compressible continuous medium, the complete system of Navier — Stokes equations is used. The proposed initial-boundary conditions made it possible to numerically determine the main gas-dynamic characteristics of the resulting three-dimensional and unsteady gas flows in free fire vortices.

The calculation results showed that during the formation of fiery vortices, several stages are distinguished in their development. The first stage is characterized by the occurrence of local gas flows diverging in the radial direction from the heating regions. The second stage is accompanied by the formation in the regions of the location of the heating sources of local vortices with opposite spin directions. The third stage is characterized by the fact that from smaller vortices due to the intense influx of external air a common large thermal vortex is formed, which receives a positive twist under the influence of the Coriolis force. At the fourth stage, with an increase in the rotation speed, a decrease in the vertical dimensions of the thermal vortex and its decay into several small ones is observed. Thus, the completion of the life cycle of one concentrated vortex is replaced by the formation of a new one. For the initial parameters, the lifetime of the concentrated thermal vortex is about one minute.

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