中国物理B ›› 2014, Vol. 23 ›› Issue (12): 124703-124703.doi: 10.1088/1674-1056/23/12/124703

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

Effect of noncircular orifice plates on the near flow field of turbulent free jets

徐敏义a, 童杏清a, 岳丹婷a, 张健鹏b, 米建春b, Nathan G. J.c, Kalt P. A. M.c   

  1. a Marine Engineering College, Dalian Maritime University, Dalian 116026, China;
    b State Key Laboratory of Turbulence & Complex Systems, College of Engineering, Peking University, Beijing 100871, China;
    c Centre for Energy Technology and School of Mechanical Engineering, University of Adelaide, SA 5005, Australia
  • 收稿日期:2014-03-20 修回日期:2014-06-12 出版日期:2014-12-15 发布日期:2014-12-15
  • 基金资助:

    Project supported by the Fundamental Research Funds for the Central Universities, China (Grant No. 3132014050), the General Science Research Project of the Education Department of Liaoning Province, China (Grant No. L2013198), the Natural Science Foundation of Liaoning Province, China (Grant No. L2014025012), and the National Natural Science Foundation of China (Grant Nos. 10921202 and 11072005).

Effect of noncircular orifice plates on the near flow field of turbulent free jets

Xu Min-Yi (徐敏义)a, Tong Xing-Qing (童杏清)a, Yue Dan-Ting (岳丹婷)a, Zhang Jian-Peng (张健鹏)b, Mi Jian-Chun (米建春)b, Nathan G. J.c, Kalt P. A. M.c   

  1. a Marine Engineering College, Dalian Maritime University, Dalian 116026, China;
    b State Key Laboratory of Turbulence & Complex Systems, College of Engineering, Peking University, Beijing 100871, China;
    c Centre for Energy Technology and School of Mechanical Engineering, University of Adelaide, SA 5005, Australia
  • Received:2014-03-20 Revised:2014-06-12 Online:2014-12-15 Published:2014-12-15
  • Contact: Xu Min-Yi E-mail:xuminyi@dlmu.edu.cn
  • Supported by:

    Project supported by the Fundamental Research Funds for the Central Universities, China (Grant No. 3132014050), the General Science Research Project of the Education Department of Liaoning Province, China (Grant No. L2013198), the Natural Science Foundation of Liaoning Province, China (Grant No. L2014025012), and the National Natural Science Foundation of China (Grant Nos. 10921202 and 11072005).

摘要:

In this paper, we experimentally investigate the near-field flow characteristics of turbulent free jets respectively issued from circular, triangular, diamond, rectangular, and notched-rectangular orifice plates into air surroundings. All the orifice plates have identical opening areas or equivalent diameters (De) and their aspect ratios (AR) range from 1 to 6.5. Planar particle image velocimetry (PIV) is used to measure the velocity field at the same Reynolds number of Re= 5×104, where Re= UeDe/ν with Ue being the exit bulk velocity and ν the kinematic viscosity of fluid. The mean and turbulent velocity fields of all the five jets are compared in detail. Results show that the noncircular jets can enhance the entrainment rate, reflected by the higher acceleration rates of mean velocity decay and spread, shorten the length of the unmixed core, expedite the increase of turbulent intensity compared with the circular counterpart shortened unmixed core, and increase turbulent intensity comparing to the circular counterpart. Among the five jets, the rectangular jet (AR= 6.5) produces the greatest decay rate of the near-field mean velocity, postpones the position at which the 鈥榓xis-switching鈥檖phenomenon occurs. This supports that axis switching phenomenon strongly depends on jet initial conditions. In addition, the hump in the centerline variation of the turbulence intensity is observed in the rectangular and triangular jets, but not in the circular jet, nor in diamond jet nor in notched-rectangular jet.

关键词: noncircular jet, free jet, turbulence mixing, axis-switching

Abstract:

In this paper, we experimentally investigate the near-field flow characteristics of turbulent free jets respectively issued from circular, triangular, diamond, rectangular, and notched-rectangular orifice plates into air surroundings. All the orifice plates have identical opening areas or equivalent diameters (De) and their aspect ratios (AR) range from 1 to 6.5. Planar particle image velocimetry (PIV) is used to measure the velocity field at the same Reynolds number of Re= 5×104, where Re= UeDe/ν with Ue being the exit bulk velocity and ν the kinematic viscosity of fluid. The mean and turbulent velocity fields of all the five jets are compared in detail. Results show that the noncircular jets can enhance the entrainment rate, reflected by the higher acceleration rates of mean velocity decay and spread, shorten the length of the unmixed core, expedite the increase of turbulent intensity compared with the circular counterpart shortened unmixed core, and increase turbulent intensity comparing to the circular counterpart. Among the five jets, the rectangular jet (AR= 6.5) produces the greatest decay rate of the near-field mean velocity, postpones the position at which the 鈥榓xis-switching鈥檖phenomenon occurs. This supports that axis switching phenomenon strongly depends on jet initial conditions. In addition, the hump in the centerline variation of the turbulence intensity is observed in the rectangular and triangular jets, but not in the circular jet, nor in diamond jet nor in notched-rectangular jet.

Key words: noncircular jet, free jet, turbulence mixing, axis-switching

中图分类号:  (Turbulent jets)

  • 47.27.wg
47.80.Cb (Velocity measurements) 47.85.lk (Mixing enhancement)