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Third Symposium on Turbulence and Shear Flow Phenomena
June, 25-27, 2003, International Center, Sendai, Japan

DOI: 10.1615/TSFP3

INTERACTION OF ACOUSTIC EXCITATION WITH A PASSIVE RING IN AN AXISYMMETRIC JET

pages 519-524
DOI: 10.1615/TSFP3.880
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RESUMO

Although the application to jet flows of both acoustic excitation and passive control methods has been studied extensively, the interaction between the two however has received little attention. In this study the interaction between acoustic excitation and a passive ring is investigated experimentally in a circular jet.
Several significant acoustic excitation modes have been identified, but in this study we concentrate on two modes namely the jet column mode of stable pairing (StD = 0.85) and the preferred mode (StD = 0.36 for the jet facility used). The jet column mode of stable pairing has been identified as promoting the formation and subsequent pairing of vortex rings which in turn leads to an enhancement in large scale transport. The preferred mode is significant as it corresponds to the most dominant and frequently occurring large-scale structures in the unperturbed circular jet (Hussain and Zaman 1981). A thin wire ring with an outer diameter slightly less than that of the nozzle is placed concentric to and a short distance downstream of the nozzle exit is used for passive control.
The introduction of the ring reduces turbulence levels and mixing layer growth rate for both modes of excitation. The ring effectively suppresses the stable pairing mode eliminating vortex pairing and dramatically altering near field development.

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