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FLAPPING MOTION OF A SUPERSONIC RECTANGULAR JET, A REDUCED ORDER MODEL STUDY

Vincent Jaunet
PPRIME Institute-UPR 3346 CNRS - University of Poitiers - ENSMA

Erwan Collin
Laboratoire d'Etudes Aérodynamiques, UMR CNRS 6609 - Université de Poitiers - ENSMA CE.A.T., 43, route de l'Aérodrome F-86036 Poitiers - France

Joel Delville
Department of Fluid Flow, Heat Transfer and Combustion Institute Pprime - UPR 3346 - CNRS - Universite de Poitiers - ENSMA CEAT - F86036 Poitiers cedex, France

Sinopsis

This article describes an aeroacoustic feedback resonant mechanism observed in a rectangular supersonic jet operating at off design conditions. Strong acoustic waves, that have a narrow band non-linear behavior, are observed in the external flow field and the jet undergoes a strong coherent flapping motion.
A low order model study, based on POD analysis, is performed on dual-time schlieren visualization, allowing to relate the external acoustic waves and the coherent motion of the jet.
The main characteristics of this aero-acoustic feedback loop are investigated and it is shown that the behavior of the jet is not exactly similar to the well known screech phenomenon. Differences between the case studied here and a classical screech phenomenon are then discussed.