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The present research examines the relationship between the large-scale structure
dynamics of a controlled jet and the far-field sound. This was achieved by exploring the
flowfield and the far field of an axisymmetric Mach 0.9 jet with a Reynolds number
based on jet diameter of approximately 7.6 x 105. The jet is controlled by eight localized
arc filament plasma actuators (LAFPA), which operate over a frequency range that spans
the jet column instability, the initial shear layer instability, and higher. Varying the phase
between the eight actuators allows excitation of azimuthal modes (m) 0, 1, 2, and 3.
The flowfield is investigated using flow visualization and particle image
velocimetry (PIV). A Reynolds decomposition of the PIV results showed the importance
of the streamwise velocity fluctuations for the symmetric azimuthal modes (m = 0 and 2),
and the cross-stream velocity fluctuations for the asymmetric azimuthal modes (m = 1
and 3). A proper orthogonal decomposition (POD) of the PIV data was performed to
extract information about how forcing affects the large-scale flow features. The first
POD mode based on v′ shows the existence has large-scale flow features from forcing
over a large range of StDF’s (0.09 to 1.08), while the first POD mode based on u′ only has
large-scale flow features from forcing around the preferred StDF of 0.36.
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