Large-Eddy Simulation of a Mach 0.75 Jet

Paper in proceeding, 2003

A large-eddy simulation (LES) of a compressible nozzle/jet configuration has been carried out. A cold Mach 0.75 jet was simulated. The Reynolds number based on the jet velocity at the nozzle exit plane and the nozzle diameter was 50,000. The Favre filtered Navier-Stokes equations were solved using a finite volume method with a low dissipative third order upwind scheme for the convective fluxes, a second order centered difference approach for the viscous fluxes and a three-stage second order Runge-Kutta time marching technique. A compressible form of Smagorinsky's sub-grid scale model was used for computation of the sub-grid scale stresses. The calculations were performed using a block structured boundary fitted mesh with approximately 3,000,000 cells. The calculations have been performed on a parallel computer, using message-passing interface (MPI). Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries. Velocity components specified at the entrainment boundaries were estimated from a corresponding Reynolds Averaged Navier-Stokes (RANS) calculation. In order to diminish disturbances caused by the outlet boundary a buffer layer was added at the domain outlet. Kirchhoff surface integration has been utilized to obtain far-field sound pressure levels in a number of observer locations using instantaneous pressure from the LES. Aerodynamic results and predicted sound pressure levels are both in good agreement with experiments. Experimental data were provided by Laboratoire d’Etude Aeròdynamiques, Poiters, France.