The linear stability dynamics of incompressible and compressible isothermal jets are
investigated by means of their optimal initial perturbations and of their temporal
eigenmodes. The transient growth analysis of optimal perturbations is robust and allows
physical interpretation of the salient instability mechanisms. In contrast, the modal
representation appears to be inadequate, as neither the computed eigenvalue spectrum nor
the eigenmode shapes allow a characterization of the flow dynamics in these settings. More …