Numerical Computation of Combustion Induced Noise Using Compressible LES and Hybrid CFD/CAA Methods

Fully compressible Large Eddy Simulations (LES) and hybrid CFD (Computational Fluid Dynamics)/CAA (Computational Aero-Acoustics) methods have been carried out to study the generation mechanism and propagation of combustion induced noise by means of two non-confined turbulent flames (premixed and non-premixed). On one hand, the sound in the near and far field was computed directly by the compressible LES. On the other hand, Lighthill's acoustic equation was simultaneously solved to quantify the acoustic sources and the resulting sound pressure level (SPL) due to turbulent flow and combustion. Also, a spectral method was applied to evaluate the noise spectrum by post-processing of RANS (Reynolds Averaged Navier Stokes) simulation. For computation of the turbulent reacting flows, the newly developed UTFC (Unified Turbulent Flame speed Closure) combustion model was employed in conjunction with both turbulence models (RANS/LES). The comparison of the results with measured data show good agreement for both flow field and noise level spectra.