Investigation of an isothermal Mach 0.75 jet and its radiated sound using large-eddy simulation and Kirchhoff surface integration

A large-eddy simulation (LES) of a compressible nozzle/jet configuration has been carried out. An isothermal Mach 0.75 jet was simulated. The Reynolds number based on the jet velocity at the nozzle exit plane and the nozzle diameter was 5.0 × 104. The Favre filtered Navier–Stokes equations were solved using a finite volume method solver with a low-dissipation 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 subgrid scale model was used for computation of the subgrid scale stresses. The computational domain was discretized using a block structured boundary fitted mesh with approximately 3.0 × 106 cells. The calculations were 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, which enabled the use of a rather narrow domain. In order to diminish disturbances caused by the outlet boundary, a buffer layer was added at the domain outlet. Kirchhoff surface integration using instantaneous pressure data from the LES was utilized to obtain far-field sound pressure levels in a number of observer locations. The predicted sound pressure levels were for all observer locations within a 3 dB deviation from the measured levels and for most observer locations within a 1 dB deviation. Aerodynamic results and predicted sound pressure levels are both in good agreement with experiments. Experimental data were provided by Laboratoire d’Etude Aeródynamiques, Poitiers, France [Jordan, P., Gervais, Y., Valiére, J.-C., Foulon, H., 2002. Final results from single point measurements. Project deliverable D3.4, JEAN—EU 5th Framework Programme, G4RD-CT2000-00313, Laboratoire d’Etude Aeródynamiques, Poitiers; Jordan, P., Gervais, Y., Valiére, J.-C., Foulon, H., 2002. Results from acoustic field measurements. Project deliverable D3.6, JEAN—EU 5th Framework Programme, G4RD-CT2000-00313, Laboratoire d’Etude Aeródynamiques, Poitiers; Jordan, P., Gervais, Y., 2003. Modeling self and shear noise mechanisms in anisotropic turbulence. In: The 9th AIAA/CEAS Aeroacoustics Conference. No. 8743 in AIAA 2003. Hilton Head, SC].