中央に長方形切欠を持つ長方形ノズルから流出する乱流噴流 : 第1報,平均速度場(流体工学,流体機械)

概要

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The mean velocity field of turbulent jet issuing from rectangular nozzle (Aspect Ratio=12.5) with a rectangular notch at the midspan, has been investigated experimentally. Four aspect ratios of rectangular notch (NAR) were 2.5, 7.5, 12.5 and 165. The Reynolds number based on the nozzle width d and the exit mean velocity U_e, was kept constant 30000 (NAR=2.5 and 7.5), 15000 (NAR=12.5) and 13000 (NAR=165), respectively. In this experiment, the variation of the potential core length and the changing rate of both the velocity and the length scales in the characteristic decay region were examined, and the present study suggested the possibility of the engineering applications. From the relationship between these results and the inward secondary flow producing both on the rectangular jet axis and the rectangular notch axis, effects of the rectangular notch on the development of the rectangular jet were clarified. Furthermore, the difference of the NAR value changes both the magnitude and the direction of the secondary flow. Finally, it is revealed that the potential core length takes the maximum value in the case of NAR=12.5, and the half velocity width b_z/d on the rectangular jet axis shows the minimum value in the case of NAR=165.
2006-05-25