The following example illustrates the application of the SDES and SBES models to a jet
emanating from a nozzle. Figure 4.8: The Computational Domain and Mesh for the Subsonic Jet Flow shows the geometry and mesh.
The round jet flow has been experimentally investigated by Viswanathan [675] at a Mach number of 
=0.9 and at a Reynolds number of 
=1.3 x 106, based on the jet diameter 
and on the bulk velocity at the nozzle exit 
. The computational mesh consisted of 4.1 x 106
hexahedral cells.
Figure 4.9: Iso-Surfaces of the Q-Criterion Colored with the Velocity Magnitude shows the turbulence structures developing with the different models. The main goal of hybrid RANS-LES models is to “transition” as quickly as possible from the steady RANS mode into the scale resolving three-dimensional LES mode.
As seen from Figure 4.9: Iso-Surfaces of the Q-Criterion Colored with the Velocity Magnitude, SDES and SBES provide a relatively rapid transition from the two-dimensional RANS to three-dimensional LES structures. The fastest transition is achieved by the SBES formulation, followed by SDES. DDES yields almost axisymmetric structures, which prevail for a noticeably longer distance from the nozzle.
Figure 4.10: Distribution of the Mean (Left) and RMS (Right) Velocity along the Jet Centerline shows the comparison with experimental data. The left plot shows the mean axial velocity along the centerline of the jet, and the right plot shows the corresponding streamwise RMS fluctuations. It is clear from both comparisons that the agreement with the data improves with the models’ ability to quickly switch into LES mode.
