The linear stability analysis of Huang [1995] has been adapted to ignore the effects of
swirl, and to allow calculation of the eigenvalues and eigenfunctions for integer, fractional, and
multiple modes of excitation. The investigation was intended to be exploratory; to gain the best
possible insights into the flow characteristics from analysis of the linearized Euler equations. All
of the azimuthal modes investigated (one-half, one, three-halves, and two) were found to lead to
the continuous, helical, vortical structure evolution in the streamwise direction of the jet. The
analysis for fractional modes of excitation predicted aphysical behavior near the jet center that
has been attributed to a unresolved questions in the mathematical analysis of the problem.
Multiple mode excitation at the axisymmetric mode and one or more azimuthal modes were
found to result in un-even, periodic, vortex-ring growth in the shear layer. An argument was
presented for the axisymmetric mode (m=O) resulting in the highest levels of entrainment for all
integer, fractional, and multiple modes of excitation. Finally the importance of the azimuthal
component of vorticity in the entrainment process was identified.
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