Large Eddy Simulations of microjets impact on supersonic jet exiting a C-D conical nozzle

The effect of multiple microjets on the acoustic noise production originating from a supersonic 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, (i.e. without fluidics). Just downstream of the nozzle lip, twelve cylindrical microjets are placed circumfer- entially, with a 60° inclination angle towards the nozzle centerline axis, in the streamwise flow direction. The pressurized massow 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 diffcult to be quantified. Thus, LES calculations have been performed to analyze the compressible flow-fleld, the shock-structure alteration and thrust evaluations associated with the fluidics