Experimental-Numerical Analysis of Turbulent Incompressible Isothermal Jets
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An experimental investigation was conducted to study the effects of Reynolds number on mixing characteristics and turbulent transport phenomena in the near and intermediate regions of free equilateral triangular and round jets issuing from modified contoured nozzles (nozzles with sharp linear contractions). Detailed velocity measurements were made using a particle image velocimetry at Reynolds numbers of 6000, 10000, 13800 and 20000. Computational fluid dynamics (CFD) was also applied to understand the flow behaviors in different Reynolds numbers. We applied standard k- turbulence model in an axisymmetric domain to conduct the numerical simulation of the round jet cases. The potential core length was the system response quantity to evaluate our simulation against the experimental results. The geometrical comparative study shows enhanced mixing in the near field of the triangular jets compared to the round jets, regardless of Reynolds number. This conclusion is supported by shorter potential core length and faster growth of turbulence intensity on the centerline of the triangular jets. The obtained data in the round jets exhibit that the jet at the lowest Reynolds number has the most effective mixing with the ambient fluid, while increase in Reynolds number reduces the mixing performance. In the triangular jets almost there is no Reynolds number effect on the measured quantities including the length of the potential core, the decay rate and the axis-switching locations. The results revealed that the asymptotic values of the turbulence intensities on the jet centerline are not only independent of the Reynolds number but also they are the same for both the round and triangular jets. Due to the specific shape of the triangular nozzle, a skewed flow pattern is observed in the near field region in the major plane while the jet is absolutely symmetric in the minor plane. The turbulence structures in all the jets studied become larger as streamwise distance increases, while there is no considerable Reynolds number or nozzle geometry effects on the size of the structures on the jet centerline.
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Volume 1C, Symposia: Gas-Liquid Two-Phase Flows; Gas and Liquid-Solid Two-Phase Flows; Numerical Methods for Multiphase Flow; Turbulent Flows: Issues and Perspectives; Flow Applications in Aerospace; Fluid Power; Bio-Inspired Fluid Mechanics; Flow Manipulation and Active Control; Fundamental Issues and Perspectives in Fluid Mechanics; Transport Phenomena in Energy Conversion From Clean and Sustainable Resources; Transport Phenomena in Materials Processing and Manufacturing Processes
