Inviscid spatial stability of a developing supersonic axisymmetric mixing layer

The instability characteristics of a developing supersonic axisymmetric mix ing layer, with basic velocity profiles having wake components, is investig ated numerically using linear inviscid stability theory in spatial formulat ion. The basic flow profiles are obtained by numerical solution of the comp ressible boundary-layer equations. For small convective Mach numbers, there are two unstable modes (the shear-lager and wake modes). If the convective Mach number is large enough, there are three unstable modes (the fast, slo w, and wake modes). The slow mode consists of several similar modes, perhap s due to the axisymmetric geometry. It is also found that there is a mode-i nterchange phenomenon between the fast and slow modes and within the slow m odes when the velocity profile has a wake component. Finally, the ratio bet ween the streamwise and azimuthal wavelengths of the most amplified save is almost constant. The normalized growth rate and the propagation angle of t he most amplified wave are consistent with previous plane mixing layer resu lts.