Vorticity formation inside and near cross-streamlined semi-cylindrical trench on flat surface
The article are devoted to elucidation of current macro- and microstructure inside of semi-cylindrical trench and near its in boundary layer on flat plate by means of investigation of vorticity distributions. Vorticity defines rotational components and physics of any liquid and gas motion, but in turbulent flows on working surfaces with geometric large-scale irregularities by indentations type and in currents with coherent vortical structures the vorticity takes the most important part in processes of mass, momentum and energy transfer. For better understanding of mechanism of indicated phenomenon this paper offers some new scientific results on experimental research of vorticity and its fluctuations fields in the region of the cross-streamlined semi-cylindrical trench on a flat surface for different flow regimes according to Reynolds numbers range (by trench diameter) Red = 1,48∙103 ÷ 2,68∙104. The experimental investigation was carried out on open-circuit wind tunnell equipped by constant temperature anemometer with hot-wire probes, laser instrumentation, vibration and acoustic analyzer. The measurements of local time-averaged velocities and velocity fluctuations discovered that the most levels of mean vorticity take place near by the streamlined surfaces and in the angular areas of trench where boundary layer is separated and vortex structures of the shear blending layer are interacted with back wall of the trench. Zones of increased voticity fluctuation levels are disposed mainly between maximum mean vorticity regions and in area formed by interaction of coherent vortical structures of shear blending layer with quasi-stable large-scale eddy generated owing to impact interaction of blending layer with trench back wall. Results of investigation may be used for efficiency estimations of transfer processes on streamlined elements of heat exchangers, engines, ships, aircrafts etc.