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Simulation of pulsated separated turbulent gas flow with positive pressure gradient in refrigerating systems channels

UDC 534-13+532.526.5:621.45.[032+034.4]

Simulation of pulsated separated turbulent gas flow with positive pressure gradient in refrigerating systems channels

Boldyrev S. V., Boldyrev A. V., Israphilov I.K., Kharchuk S.I.

Abstract
Numerical simulation of compressible gas pulsated separated turbulent flow in diffuser behind diaphragm in axisymmetric setup is carried out. High-Reynolds number quadratic turbulence model is applied. The data for distribution of skin-friction and pressure coefficients on channel wall and of kinetic turbulent energy along channel axis are obtained at Re = 33000 for three values of angle between the channel axis and wall. The good agreement between the simulation results and the experimental data with regard to the critical Strouhal number value (Sh) of 0.054 (which determines minimal length of separated zone) is achieved for cylindrical channel (α = 0o). Under conditions in question it has been observed that critical Strouhal number value had no detectable fluctuation in the α angle range between 0о and +3о. More significant reduction of recirculating zone length by comparison with the one observed in cylindrical channel is at α angle value of +1o, whereas just slight stabilization of the separation zone size in the Strouhal number range from 0.05 to 0.0076 is discovered at the angle of +3о. It has been known that RANS equations applying in turbulent models leads to overestimation of recirculating zone length in separated turbulent flow at high frequencies of imposed pulsations and thus additional researches are necessary for improvement of the results obtained. Nevertheless, the data of critical Strouhal number value might be useful for the research of the boundary layer separation control possibilities.

Keywords: numerical simulation, pulsated flow, separated flow, turbulent flow, pressure gradient

All references

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