Large Eddy Simulations of Microjets Impact on Supersonic Jet Exiting a C-D Conical Nozzle

Authors: Semlitsch, B., Mihaescu, M, Fuchs, L.F., Gutmark, E.
Document Type: Article
Pubstate: Published
Journal: 19th AIAA/CEAS Aeroacoustics Conference (34th AIAA Aeroacoustics Conference)
Volume: AIAA 2013-2139  
Year: 2013


The effect of multiple microjets on the acoustic noise production originating from a super-sonic jet exhausting a gas turbine engine is studied numerically using the Large Eddy Simulation (LES) approach. The nozzle exit design Mach-number is 1:56, while the total temperature ratio is kept to 1:27. The nozzle contour is a double cone converging-diverging nozzle. The emerging jet is slightly over-expanded. A double shock-diamond pattern develops in the supersonic flow. The study focuses on the changes in the flow pattern, the shock-associated noise and the radiated near-field acoustics when using fluidics as compared with a baseline case, (i.e. without fluidics). Just downstream of the nozzle lip, twelve cylindrical microjets are placed circumferentially, with a 60 inclination angle towards the nozzle centerline axis, in the streamwise flow direction. The pressurized mass-flow feeding the microjets is assumed to be initially at ambient conditions. The amount of pressurization is given as an Injection Pressure Ratio (IPR) and represents the investigation parameter. Acoustic based experiments performed at University of Cincinnati (UC) exhibited acoustic benefit when using the mentioned set-up for the microjets. However, the impact that injection had on the flow-field was difficult to be quantified. Thus, LES calculations have been performed to analyze the compressible flow-field, the shock-structure alteration, and to evaluate the thrust associated with the fluidics.