The presence of tones in the acoustic far field of isothermal round jets for angles relative to the flow direction is investigated for Mach numbers between and 2 based on data from both experiments and large-eddy simulations. For all Mach numbers, as observed in the jet near-nozzle region in previous studies, peaks are found in the far-field pressure spectra regardless of the nozzle-exit boundary-layer properties. They emerge near the cutoff frequencies of the free-stream upstream-propagating guided jet modes predicted by a vortex sheet model, sharply for but more weakly for lower Mach numbers. The variations of their characteristics with the radiation angle are shown. As the angle increases, the peaks are more prominent, and the most apparent ones are related to lower azimuthal modes. Thus, peaks associated with the axisymmetric mode strongly predominate in the upstream direction.
Tones in the Acoustic Far Field of Jets in the Upstream Direction
AIAA Journal ; 60 , 4 ; 2397-2406
2021-11-30
10 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch