• hybrid model
• bluff-body

A new hybrid RANS/LES approach is proposed.
The key feature of this approach is a blending between
two eddy-viscosities, one given by the k-epsilon RANS
model and the other by the Smagorinsky VMS-LES
(variational multiscale LES) closure. The blending
is set by a parameter teta: VMS-LES mode is active when teta=0,
RANS mode if teta=1, a hybrid mode for 0<theta<1.
The proposed hybrid model has been applied to the numerical
simulation of the flow around a square cylinder at Re_L=22000.
Three different parameters (based on viscosity ratio,
time ratio and length ratio) are tested.
The results obtained with this new hybrid
approach are compared with those obtained
using the LNS approach for two different grid resolutions; comparisons
with experimental data in the litterature are also provided.
The sensitivity of the model to some setting parameters
(the inflow value of the turbulent kinetic
energy, k_0 and the parameter delta in the
approximate wall treatment) is also analysed.
The hybrid model has been also applied to the simulation of the flow
around a circular cylinder at Re_D=140000.The results are compared
with those obtained using the DES approach. Also for this case,
comparisons with experimental data in the litterature are provided.