Structure of the natural convective flow above to the horizontal surface with localized heating

• Published in: International journal of heat and mass transfer 2020-05, Vol.152, p.119492, Article 119492
• Main Authors: Khrapunov, Evgenii, Chumakov, Yuri
• Format: Article
• Language: English
• Subjects: Bifurcations; Computer simulation; Convective flow; Flow characteristics; Flow regimes; Heat transfer; Identification methods; Natural convection; Numerical methods; Puffing; Temperature distribution; Thermal plumes
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2020.119492

•The increase of the surface temperature of the plume source (the equivalent of an increase of Grashof number) leads to the appearance of a second stable flow regime.•The steady flow regime of the plume (observed at small Grashof numbers) is replaced by a periodic one the near-wall layer of the plume is destroyed as a result of the periodic formation of toroidal vortices.•The periodic formation of toroidal vortices leads to a change in the distribution of average values temperature and velocity in the plume.•Shown how the form of instantaneous values of temperature transforms in time and from the periphery of the disk to its center.•The change in the local and integral heat transfer coefficients as a result of the presence of “puffing” is presented. Pure thermal plumes have been the subject of study for the past decades. The active development of experimental and numerical research methods allowed to identify the flow characteristics in the entire region of the plume formation. Nevertheless, the bifurcation discovered in the last ten years remains to be studied, in the authors' opinion, poorly. Until now, there is no general conception of the existence of several stable flow regimes and the key features of the unsteady regime. In this paper results of an experimental and numerical study of pure thermal plume structure in the near-hot-wall region at moderate Grashof numbers are presented. Experimental data on the general flow structure and temperature field are supplemented by the results of numerical simulation. The analysis of changes in instantaneous and average values is carried out, in particular, the geometric characteristics of the near-wall layer are determined. Additionally, data on the characteristics of heat transfer, information on which in modern studies is usually limited and is fragmentary, are presented.