Numerical and physical simulations of a laminar separation fl ow over a single spherical dimple built in the lower wall of the rectangular-section plane-parallel channel of a water tunnel were performed on the basis of the multiblock computational technologies realized in the VP2/3 package. The vortex mechanism of intensifi cation of the heattransfer processes in this dimple was analyzed with special emphasis on the identifi cation of the vortex-jet structures self-generated in it.Keywords: separation fl ow, spherical dimple, plane-parallel channel, hydraulic losses, heat exchange, water tunnel, procedure of pressure correction, Rhie-Chow approach, multiblock computational technologies, VP2/3 package, visualization.Introduction. Identifi cation of the tornado-like vortex-jet structures self-generated in the separation fl ow over a single spherical dimple built in the wall of a channel continues to attract the attention of researchers to the present day [1-6]. The main reason for this interest is the need for a comprehensive knowledge of the vortex mechanism of intensifi cation of the heat exchange on surfaces with dimples. A pressing problem is also the verifi cation of the results of a corresponding computer imitation analysis. In this connection, a complex numerical and physical investigation on the visualization of a fl ow over a single spherical shallow dimple built in the lower wall of the rectangular-section plane-parallel channel of the water tunnel of the A. N. Krylov Central Scientifi c-Research Institute, performed by us with the use of the VP2/3 package developed at the St. Petersburg State University of Civil Aviation seems to be urgent.Genesis of the Problem. During more than 50 years the problem of the vortex intensifi cation of the heat exchange on surfaces with dimples has attracted the attention of scientists engaged in investigations related to thermal physics. The most important methodological aspect of this interesting problem is consideration of the mechanism of the indicated process by the example of the heat exchange in the neighborhood of a single spherical shallow dimple built in a plane wall. It is precisely this aspect that is the focus of attention for us in the present work. Therefore, we will briefl y review physical and numerical investigations on the convective heat exchange in the neighborhood of a single dimple. It makes sense to restrict our consideration to a spherical dimple because such dimples are most easy to manufacture. It should be noted that it is precisely these dimples for which the most complete results have been obtained.One of the fi rst signifi cant investigations on the fl ow over a single dimple in the form of a hemispherical cavity has been performed by R. Snideker and K. Donaldson in the 1960s and presented in the format of a two-page article [7], in which the transformation of the vortex structures formed within such a cavity as a result of the cyclic transfer of the tornadolike jets self-generated in it from one half of the cavity to its other half and backw...

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The creation of all heat exchangers supposes the establishment of a quantitative and qualitative relationship between the flow and heat flux distribution at heat transfer surfaces. The paper presents the study’s results of the vortex flow’s structure and heat transfer near two circular cylinders. The distance between the cylinders ranged from 0.5d to 4d during the experiments (here d is the diameter of the cylinders). The vortex flow’s patterns in hydro- and wind tunnels in the Reynolds numbers’ range from 4000 to 40,000 are compared. To study heat transfer near the cylinders, gradient heat flux measurement was used. In aerodynamic experiments, both cylinders were heated with saturated steam, ensuring a constant surface temperature of the cylinder. The results showed an agreement of the flow patterns. The effect of distance and flow velocity on the flow around the second cylinder is revealed: there may be cases when the second cylinder is at rest, in other cases it fluctuates. Gradient heatmetry revealed a decrease in the level of fluctuations near the second cylinder. However, the average Nusselt number for the second cylinder is expectedly lower than for the first.

Object and purpose of research. The object of the research is the flow pattern around ship models and engineering structures. The purpose is to optimize their outer lines. Materials and methods. The studies were carried out in a vertical hydrodynamic tunnel with a transparent test section using flow visualization methods. Main results. After the series of studies, technical solutions have been developed and implemented on sea-going ships and marine engineering structures. The paper shows that these studies are strongly recommended at early stages of ship design, especially for the structures with flow separations, like funnels, helipads, upper decks, air inlets, bridge spans, etc. Conclusion. The results indicate that the vertical hydrodynamic tunnel can be successfully used for development of outer lines for hulls and other engineering structures with flow separations.