Numerical RANS/URANS simulation of combustion noise

In the present work, numerical simulation tools for two different combustion noise source mechanisms are presented. The generation and propagation of entropy noise is computed directly using a compressible CFD approach in combination with appropriate acoustic boundary conditions. The EntropyWave Generator (EWG) experiment is taken for validation of the proposed approach and for evaluating the acoustic sources of entropy noise. Simulation results of pressure fluctuations and their spectra for a defined standard test configuration as well as for different operating points of the EWG agree very well with the respective experimental data. Furthermore, a new numerical approach called RPM-CN approach was developed to predict broadband combustion noise. This highly efficient hybrid CFD/CAA approach can rely on a reactive RANS simulation. The RPM method is used to reconstruct stochastic broadband combustion noise sources in the time domain based on statistical turbulence quantities. Subsequently, the propagation of the combustion noise is computed by solving the acoustic perturbation equations (APE-4). The accuracy of the RPM-CN approach will be demonstrated by a good agreement of the simulation results with acoustic measurements of the DLR-A flame. The high efficiency and therefore low computational costs enable the usage of this numerical approach in the design process.

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