Frequency selection in globally unstable round jets

Abstract : The self-sustained formation of synchronized ring vortices in hot subsonic jets is investigated by direct numerical simulation of the axisymmetric equations of motion. The onset of global instability and the global frequency of synchronized oscillations are examined as functions of the ambient-to-jet temperature ratio and the initial jet shear layer thickness. The numerical results are found to follow the predictions from nonlinear global instability theory; global instability sets in as the unperturbed flow is absolutely unstable over a region of finite streamwise extent at the inlet, and the global frequency near the global instability threshold corresponds to the absolute frequency of the inlet profile. In strongly supercritical thin shear layer jets, however, the simulations display global frequencies well above the absolute frequency, in agreement with experimental results. The inner structure of rolled-up vortices in hot jets displays fine layers of positive and negative vorticity that are produced and maintained by the action of the baroclinic torque. © 2007 American Institute of Physics.
Complete list of metadatas

Cited literature [19 references]  Display  Hide  Download

https://hal-polytechnique.archives-ouvertes.fr/hal-01023085
Contributor : Denis Roura <>
Submitted on : Sunday, July 20, 2014 - 9:29:58 AM
Last modification on : Wednesday, August 7, 2019 - 12:18:08 PM
Long-term archiving on : Thursday, November 20, 2014 - 6:14:44 PM

File

lesshafft2007rp-2pp.pdf
Publisher files allowed on an open archive

Identifiers

Citation

Lutz Lesshafft, Patrick Huerre, Pierre Sagaut. Frequency selection in globally unstable round jets. Physics of Fluids, American Institute of Physics, 2007, 19 (5), pp.054108. ⟨10.1063/1.2732247⟩. ⟨hal-01023085⟩

Share

Metrics

Record views

381

Files downloads

325