Tertiary Flow Effects on a Co-axial Ducted Jet.

Authors: Mihaescu, M, Kastner, J.F., Gutmark, E.
Document Type: Conference
Pubstate: Published
Journal: 50th AIAA Aerospace Sciences Meeting, 9-12 January 2012, Nashville, TN, USA
Volume: AIAA-2012-0064   14 pages
Year: 2012


Long duct mixed flow exhaust systems operate as noise suppression devices under the concept that the surrounding secondary long duct shields some of the fine-scale turbulent mixing noise generated between the primary and secondary streams. Numerical results concerning a round co-axial ducted jet at Baseline (without tertiary flow effects) are compared against data obtained for two tertiary flow conditions of 0.15 and 0.30 co-flow Mach numbers (Mcf), respectively. The computations are carried out by using the Reynolds-Averaged Navier-Stokes (RANS) formulation with Realizable k-? turbulence model. At Baseline, comparisons between the computational predictions and Stereoscopic Particle Imaging Velocimetry (SPIV) experimental data just downstream of the nozzle exit show a good agreement. In the fully merged zone of the jet, self-similarity is achieved at the downstream axial location of x ~ 9D (Baseline case, Mcf = 0), where D is the diameter of the long duct nozzle’s exit. The tertiary flow increases the length of the potential core region while limiting the radial spread of the jet. With tertiary flow, self-similarity is achieved at x ~ 11D and at x ~ 13D for the co-flow Mach numbers (Mcf) of 0.15 and 0.30, respectively. When considering a tertiary flow of Mcf = 0.30, the maximum turbulence intensity levels in the outer shear layer of the jet decreased to about 20% of the baseline case.