Large Eddy Simulation for the Analysis of Jet Noise Suppression Devices

Licentiatavhandling, 2007

Stricter noise regulations for commercial aircraft have increased interest in noise reduction techniques within the aerospace industry. To meet the requirements new noise suppression technologies have to be delveoped and the numerical methods need to be validated and possibly improved for the correct assessment of these new technologies. This thesis deals with numerical predictions of flow and far-field acoustic signature for mixer-ejector nozzle configurations including acoustic liners. The flow field predictions are obtained using large eddy simulation and Kirchhoff's surface integration technique is used for predicting the far-field noise. A time-domain broadband impedance boundary condition formulation is used for modeling a Helmholts type acoustic liner. In all cases studied, the nozzle geometry is included in the calculation domain. For the mixer-ejector nozzle configuration the flow field is well captured and the target mass flows were obtained indicating that the prediction was successful. For the acoustic liner model the implementation has proven to be robust and cost effective. In validations against experimental benchmark test cases the model has given very good agreement in cases with both stagnant conditions and grazing flow.