オリフィス自由噴流のノズル板厚さによる流動制御(流体工学,流体機械)

概要

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The effects of orifice plate thickness t on an orifice free jet for nozzle diameter of d_o=10.0mm and contraction area ratio of CR=0.27 were investigated experimentally. Visualized images of the water submerged jet showed large coherent vortex structure depending on the orifice plate thickness t.Hot-wire measurements were conducted at a high Reynolds number, Re=1.5×10^4, for various orifice plate thickness ranged from t/d_o=0.01 to 1.5. A comparison with a pipe jet flow having a fully developed velocity profile of the turbulent pipe flow was also performed. The effect of vena contracta was apparently observed for smaller t and a similar flow behavior as the pipe jet was seen with increasing t. Sudden increase of the jet center turbulent intensity at the nozzle exit occurred for the jet of t/d_o=0.5, which has shorter potential core length and lower dominant frequency than the other jets, indicating that the flow fluctuated unsteadily at the nozzle exit. It is also found that the jet of t/d_o=0.5 entrained ambient fluid remarkably and widely spread.
社団法人日本機械学会の論文
2008-09-25