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The results of numerical simulation of the puffing regime of a pure thermal plume, which forms above a slightly inclined (with respect to the horizon) surface have been presented. The flow structure in the near-wall region was investigated and the fields of the velocity components were analyzed. Particular attention was paid to the analysis of the distribution of instantaneous, time- and surface-averaged values of the heat transfer coefficient α. Based on the presented results, it was concluded that there was an optimal angle of inclination of the surface maintaining the most efficient heat transfer with a developed periodic flow regime.

The results of an experimental study of a free convective boundary layer on a vertical heated surface are presented in this paper. Particular attention was paid to studying the laminar-turbulent transition zone and determining the boundaries of this zone. The main goal of the present work was to study the possibility of controlling the transition processes by acting on it with various large-scale obstacles located in the region of the laminar section of the boundary layer. A studied free-convection boundary layer is formed on a vertical aluminum plate 90 cm wide and 4.95 m high. Based on the obtained results, it can be confidently stated that with the help of large-scale obstacles, it is possible to significantly reduce the length of the transition zone and thereby bring the beginning of the region with developed turbulent heat transfer closer to the front edge of the surface. Thus, obstacles can be considered as passive elements for controlling the intensity of heat transfer.

New experimental data that quantitatively characterize fields of the mean velocity and temperature, the intensity of temperature and velocity pulsations, and also velocity-temperature correlations in the near zone of a circular cylinder placed on the vertical heated surface at the height corresponding to the fully turbulent flow regime have been presented. Systematic measurements in the middle vertical plane (the plane that contains the cylinder axis) were performed using constant temperature anemometer and resistance temperature detectors. The experimental data was compared with numerical simulation one obtained through solving the RANS equations. The overall data were in good agreement and indicated the cardinal restructuring of the flows both before the cylinder (where the horseshoe-shaped vortex formed) and behind the obstacle (in the near separated area and the recovery one of the natural convective near-wall layer).