Linear stability of a compressible coaxial jet with continuous velocity and temperature profiles

This paper describes an investigation of the stability of a jet with velocity and temperature profiles characteristic of the exit region for a turbofan engine. Because the bypass stream mixes with both the exhaust and the ambient air, these profiles contain thin layers in which the velocity and temperature may vary rapidly. As a consequence, multiple instability modes are possible. In accordance with Rayleigh's theorem for axisymmetric incompressible shear flows, it turns out that there are three possible modes, only two of which are unstable. We consider the effect on spatial growth rates of varying the diameter and velocity ratios, compressibility, and azimuthal wavenumber. Radiating modes, that are possible when the primary jet is heated, are also studied. (c) American Institute of Physics.