A study of the interaction and coupling of wavepackets in supersonic twin jets using plane-marching PSE*

Supersonic twin jets are a common configuration encountered in the propulsion systems of high-speed flight vehicles and rocket launchers. The interaction between the fluctuating pressure fields of the jets leads to their coupling and results in more complex physical mechanisms than those of a single jet. In this work, we apply plane-marching Parabolized Stability Equations to model the large-scale turbulent structures, often referred to as wavepackets, responsible for the dominant part of the noise in twin-jet configurations. By analyzing several frequencies for different jet spacings, the following conclusions are reached:

First, the jet-jet interaction significantly modifies the dynamics of the wavepackets, altering their amplification and convection speed. For the non-toroidal modes, the coupling favors flapping motions of the jet plumes over the helical motions that dominate in single jets. Second, the Mach-wave noise radiation associated with the wavepackets is also altered beyond the linear superposition of emission by two incoherent jets. An overall reduction of the acoustic emission is found for most modes and azimuthal angles, while the pressure radiated in the direction perpendicular to the jet-containing plane is increased up to 50% for some oscillation modes.