Methodology for analysis of postshock oscillations during pulse-triggered instability

Past experimental studies have suggested that the propagating shock wave as sociated with pulse-triggered instability in solid rocket motors is followe d by postshock oscillations. A new methodology was developed to confirm the existence and evaluate the nature of these oscillations. This methodology is composed of a new time-marching frequency and a time-frequency analysis. The new time-marching analysis follows the evolution of the time-averaged frequency content of the postshock oscillations throughout a firing, wherea s with the time-frequency analysis, it is possible to obtain a qualitative estimate of the temporal evolution of the amplitude of the frequency conten t of postshock oscillations for a single shock-wave cycle. The new methodol ogy was developed and tested with model signals and then successfully appli ed to a sample experimental signal.