Analysis of Unsteady Flow in Over-expanded Nozzle
Résumé
An over-expanded jet in a Truncated-Ideally Contoured
(TIC) nozzle is investigated to identify the phenomena involved
in the generation of lateral pressure forces. The
operating conditions correspond to the generation of wall
pressure fluctuations of maximal amplitude for the present
geometry. Synchronized time-resolved velocity and wall
pressure data are measured in planes normal to the jet axis
downstream of the nozzle and along azimuthal rings of pressure
sensors within the separated region in the nozzle. The
first fluctuating modes of internal pressure and external velocity
are found to be significantly correlated in a narrow
frequency range. A Delayed Detached Eddy Simulation
(DDES) is carried out to reproduce the global flow dynamics.
It is shown in this case that lateral forces are dominated
by the signature of this tonal behaviour.