Back to Search Start Over

A closure mechanism for screech coupling in rectangular twin jets.

Authors :
Jinah Jeun
Gao Jun Wu
Lele, Sanjiva K.
Source :
Journal of Fluid Mechanics; 5/25/2024, Vol. 987, p1-26, 26p
Publication Year :
2024

Abstract

The twin-jet configuration allows two different scenarios to close the screech feedback. For each jet, there is one loop involving disturbances which originate in that jet and arrive at its own receptivity point in phase (self-excitation). The other loop is associated with free-stream acoustic waves that radiate from the other jet, reinforcing the self-excited screech (cross-excitation). In this work, the role of the free-stream acoustic mode and the guided-jet mode as a closure mechanism for twin rectangular jet screech is explored by identifying eligible points of return for each path, where upstream waves propagating from such a point arrive at the receptivity location with an appropriate phase relation. Screech tones generated by these jets are found to be intermittent with an out-of-phase coupling as a dominant coupling mode. The instantaneous phase difference between the twin jets computed by the Hilbert transform suggests that a competition between out-of-phase and in-phase coupling is responsible for the intermittency. To model wave components of the screech feedback while ensuring perfect phase locking, an ensemble average of leading spectral proper orthogonal decomposition modes is obtained from several segments of large-eddy simulation data that correspond to periods of invariant phase difference between the two jets. Each mode is then extracted by retaining relevant wavenumber components produced via a streamwise Fourier transform. Spatial cross-correlation analysis of the resulting modes shows that most of the identified points of return for the cross-excitation are synchronised with the guided jet mode self-excitation, supporting that it is preferred in closing rectangular twin-jet screech coupling. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00221120
Volume :
987
Database :
Complementary Index
Journal :
Journal of Fluid Mechanics
Publication Type :
Academic Journal
Accession number :
178499802
Full Text :
https://doi.org/10.1017/jfm.2024.376