DOI: 10.1615/TSFP3
INTERACTION OF ACOUSTIC EXCITATION WITH A PASSIVE RING IN AN AXISYMMETRIC JET
RÉSUMÉ
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.