  The present work is concerned with a study of large eddy simulations (LES) of
unsteady turbulent jet flows. In particular, the present analysis is focused on
the effects of the subgrid-scale modeling used when a second-order spatial
discretization methodology is employed for the numerical simulations. The
present effort addresses perfectly expanded supersonic jets, because the
authors want to emphasize the effects of the jet mixing phenomena. The LES
formulation is discretized using the finite difference approach, after the
equations are rewritten in a generalized coordinate system. Both space and time
discretizations are second-order accurate and an explicit time march is
adopted. Special care is dedicated to the discretization of the energy equation
to appropriately model the set of filtered equations appearing in the LES
formulation. The classical Smagorinsky, the dynamic Smagorinsky and the Vreman
models are the subgrid-scale closures selected for the present work. The
computational results are compared to data in the literature to validate the
present simulation tool. Results indicate that the characteristics of numerical
discretization can be as important as the effects of the subgrid-scale models
for such low-order spatial discretization schemes. A detailed analysis is
presented for the performance of each subgrid closure in the numerical context
here considered.
