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First name, Middle name, Last name, Scientific degree, Scientific rank, Current position. Full and brief name of the organization, The organization address.Posokhin V.N. – doctor of technical sciences, professor E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Ziganshin A.M. – candidate of technical sciences, associate professor E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Gorohova A.Y. – student E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it Kazan State University of Architecture and Engineering The organization address: 420043, Russia, Kazan, Zelenaya st., 1
Title of the articleAbout natural convection over the horizontal heat sources
Abstract.This work presents results of numerical research of natural convection above the horizontal plate flush with the surrounding surface. Arising jet can be divided into three sections – initial where the flow has a laminar flow regime, continue to increase the height of the flow begins to lose stability – a zone of transition flow, and with a certain height – developed turbulence jet. The concept of the Rayleigh number for an arbitrary section Rax, as the sum of Ra0 – shows the ratio of gravity forces and viscous forces in the area adjacent to the horizontal heat source, and ?Rax additive characterizes the change in the number of Rayleigh on the jet height. Conducted a series of numerical studies using laminar model i.e. solve a system of equations of fluid motion without the use of RANS approach. Solving the tasks with changing of heat flux of the source, so that Ra0 was within 8•102?104, which corresponds to a laminar mode of heat transfer. At the same time, Rax values depending on the height changed significantly. According to the numerical results plotted the graphs of changes of relative axial velocity and excessive temperature and relative Rayleigh number . There was some critical height xcr – the beginning of the transient zone. Also determined the dependence . Further results of numerical modeling using RANS approach are shown. The graphs of the relative change in axial velocity using different turbulence models are plotted. It is shown that, k-? model reproduce the kinematics of the flow better than the other on the main zone of the jet, and on the initial section – laminar model.
Keywords.natural convection, flat heat source, flow regimes, the critical value of the Rayleigh number, turbulence models.
For citations:Posokhin V.N., Ziganshin A.M., Gorohova A.Y. About natural convection over the horizontal heat sources // Izvestiya KGASU. 2016. №2(36) P.140-145.

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