Analysis of self-sustained oscillation sources in segmented flows

Abstract.

The analysis of self-sustained oscillations in segmented flow generated through porous walls has been carried out over a wide range of velocity levels; in fact, we studied a cold gas flow induced by injection through different wall injecting blocks. We have attempted in this study to analyse the potential unstable development occurring in solid propellant rocket motors. We lay emphasis upon the phenomenon of wall vortex shedding insofar as it conduces to acoustic mode resonance in the whole chamber, within whose confines impingement of such structures generates a source of noise. It is on account of segmented flow that the thin shear layer develops and that the aforementioned vortex shedding comes to induce aero-acoustic coupling. Subsequent experimental results highlight a link in such flows between these two noise sources – they also allow one to observe a pronounced form of selectivity in the energy transfer, i.e. in longitudinal acoustic mode amplification, which has an attested effect upon all of the pressure oscillations in the chamber.