Shock separation and resonance in rocket nozzles

This paper aims to identify if a screech-like resonance loop is responsible for the side-load generation in rocket nozzles as hypothesized in recent studies. Reynolds-averaged Navier-Stokes (RANS) simulations are conducted for the flow inside a subscale thrust-optimised parabolic (TOP) nozzle for different nozzle pressure ratios (NPRs). Linear stability analysis (LSA) is performed on the resultant mean flow fields to characterise the waves involved in the resonance loop. Finally, the weakest-link model is implemented across several streamwise positions to provide a prediction for the peak frequency at which resonance may occur. The LSA suggests the presence of both upstream and downstream-propagating waves associated with the helical m = ±1 azimuthal mode. Moreover, the predicted peak frequencies from the weakest-link model show a strong agreement with past literature hence strengthening the proposed hypothesis.