Wavepacket models for subsonic twin jets using 3D parabolized stability equations

Investigation of supersonic twin-jet coupling using spatial linear stability analysis

“…All the modes of this section are obtained as in Rodríguez et al. (2018). In summary, the spectrum containing eigenmodes related to different symmetries and azimuthal wavenumbers is obtained as a function of frequency, and the relevant modes are extracted for the analysis.…”

“…Following Rodríguez et al. (2018), the different modes in the twin-jet system can be classified using the nomenclature XY, where is the dominant azimuthal wavenumber of the disturbance in each jet, and X and Y are related to the symmetry around the and axes, which are also connected to the Floquet coefficient as shown in table 1. Thus, modes related to azimuthal wavenumber (0S and 0A) and those following the symmetry SS and SA can potentially be identified among the POD modes.…”

“…In a similar approach, Rodríguez et al. (2018) used LSA and parabolised stability equations to analyse the development of the KH mode for different spacings and mode symmetries for a subsonic jet.…”

“…(2021), and on the formulation of Rodríguez et al. (2018), adapted to take advantage of the symmetry of the problem (as in Lajús et al. 2019).…”

Intermittent modal coupling in screeching underexpanded circular twin jets

“…Firstly, the growth rate of the various azimuthal modes is a function of Mach number (and thus NPR); at certain operating conditions a change in which azimuthal mode is dominant will produce a change in tonal frequency. In twin-jet systems, this change may be a change in the coupling between the jets, rather than a change in the azimuthal mode of the individual jets (Rodríguez, Jotkar & Gennaro 2018). Secondly, a change in the number of contemporaneous vortical structures and acoustic waves can produce a discrete change in frequency, as demonstrated in Gao & Li (2010); such a change may be driven by a change in effective source location (Mercier, Castelain & Bailly 2017).…”