Screech predictions in military-style rectangular nozzles

In this work, the characteristics of the screech resonance loop of a military-style, convergingdiverging nozzle are explored using a range of experimental and modelling techniques. Schlieren measurements at both major and minor axes were performed at a range of nozzle pressure ratios (NPR), on which spectral-proper orthogonal decomposition was performed. This allowed for the identification of the staging behaviour in these nozzles, and also provided some information about the symmetry of the waves involved in the resonance loop. Further analysis was performed using particle-image velocimetry (PIV) data, where the velocity fields associated with the different screech modes were obtained by modal decomposition. The PIV data was also used to provide mean flows for linear-stability analysis (LSA), which was used to predict the wavenumbers of the different waves involved in the resonance loop.