Screech feedback reinforcement by coupling of twin rectangular jets

We use high-fidelity LES data to investigate aeroacoustic coupling in twin supersonic rectangular jets with an aspect ratio of 2. The LES data was validated against the experiments conducted at University of Cincinnati. Twin geometry allows two different screech feedback loops. For each jet, one loop involves with upstream disturbances originating from itself (self-excitation), which can be internal or external modes. The other feedback loop is completed by disturbances arriving from the other jet (cross-excitation). These paths are extracted from the leading SPOD modes at the fundamental screech frequency after a wavenumber decomposition in the streamwise direction. Assuming the maximum receptivity at the nozzle exit, the cross-correlation analysis identifies points of return where upstream disturbances originating from such a point satisfy the resonance condition. The current analysis suggests that, while both internal and external modes play a role in the self-excitation feedback loop, some of the identified points of return for the cross-excitation are synchronized with the internal mode self-excitation. Such synchronization of the self- and cross-excitation modes disappears at non-resonating frequencies.