The effect of diffuser dimple's shape on its flow-around pattern
Fluid, gas and plasma mechanics
Аuthors*, **, ***,
Kazan National Research Technical University named after A.N. Tupolev, KNRTU-KAI, 10, Karl Marks str., Kazan, 420111, Russia
This experimental study is aimed at the searching an easy-to-manufacture shape of the previously submitted by the authors highly efficient surface thermal exchange intensifier of a separation type with high functioning intensity of large-scale vortex structures, namely two-cavity diffuser dimple. This dimple, placed in an array of dimples demonstrated a higher level of heat dissipation, exceeding more than three times the heat dissipation while a smooth plate flow-around. It was accepted as reference. The high level of thermal effectiveness of this dimple is associated with implementation of optimal relative height of the rib separating its hollows, the diffuser shape of its hollows for the backflow, as well as with their slope in plan view of the relative direction of the main flow.
Based on visualization of the flows and determination of the pressure coefficient Cp in the bottom part of the studied dimple’s variants the experimental data was obtained on its shape in terms of the self-organizing large-scale vortex structures.
The ways of geometric shape of the two-hollow diffuser dimples’ simplifying were studied, and, hence, its manufacturing technology under condition of preserving the intensity and continuity of large-scale vortex structures functioning.
The authors established that without the hollows’ separating rib, when the entry edge is described by the line of radial contour, two-hollow dimple passes into the class of one-hollow dimples with permanently functioning single large-scale vortex structure. The rarefaction level, however, in the in the dimple’s epicenter decreases compared to the two-hollow diffuser dimples.
The performed comparative studies revealed the existence of the rational geometry of one-hollow diffusor dimple of a separation type ensuring permanent functioning of vortex structures. This dimple allows much simpler manufacturing technology compared to the two-hollow diffuser dimples. However, it is inferior to the latter in the intensity of large-scale vortex structures. Thus, following the two-hollow diffuser dimple structure it is necessary to explore and find such installation angle relative to the main flow that provides maximum vortex intensity. This is essentially the algorithm for further optimization of the easy-to-manufacture one-hollow diffuser dimple of separation-type studied here.
Keywords:visualization, dimple, turbulent flow, pressure coefficient, self-organizing large-scale vortex structure, manufacturability
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