The Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF)
Online ISSN : 2424-2888
2005
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VORTEX DYNAMICS IN STARTING SQUARE JETS(Special Nozzle)
S.C.M. YuJiaoJian AiAdrian Wing-Keung Law
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CONFERENCE PROCEEDINGS FREE ACCESS

Pages 209-214

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Abstract
This paper presents the results of an experimental study on starting square jets at three Reynolds numbers (R_e=2358, 3528, 4716) utilizing Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV). Vortex leapfrogging and coalescence were found to appear at the lowest Reynolds number investigated while vortex pinch-off tended to appear at higher Reynolds numbers. The 'imperfect' leapfrogging between the third and the fourth vortex rings appears to promote growth of instability which leads to the transition to turbulence. The maximum circulation that a vortex ring can attain during its formation is reached at the non-dimensional time (t*=tW_0/D_e) within the range of 1.0〜2.33 which is lower than the universal time scale obtained by Gharib et al. for the circular jets with uniform initial velocity distribution. Axis switching was found to play an important role for the vortex development in square jets.
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© 2005 The Japan Society of Mechanical Engineers
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