Large-eddy simulations of co-annular turbulent jet using a Voronoi-based mesh generation framework

Large eddy simulations are performed for a cold ideally-expanded dual-stream jet issued from cylindrical co-axial nozzles, with supersonic primary stream (Mach number M_1 = 1.55) and subsonic secondary stream (M_2 = 0.9). The geometry includes the internal screw holes used to fasten the two nozzles together and to the plenum chamber. These slanted cylindrical holes over which the secondary stream flows were not covered in the experiment and were seamlessly captured in the computational mesh thanks to a novel grid generation paradigm based on the computation of Voronoi diagrams. A simulation with the screw holes covered is also performed and the preliminary results tends to indicate that these features have minimal impact on the flow and acoustic fields for the present operating conditions. As expected, the present dual-stream configuration with subsonic annular stream surrounding the primary supersonic stream features a reduced shear-layer growth, a longer potential core and a lack of strong Mach wave radiation. A long LES database is currently being collected for analysis and modeling of wavepackets and noise sources in such complex turbulent jets.