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Trailing edge noise generated by turbulent flow traveling past an edge of anairfoil is one of the most essential aeroacoustic sound generation mechanisms.It is of great interest for noise problems in various areas of industrialapplication. First principle based CAA with short response time are needed inthe industrial design process for reliable prediction of spectral differencesin turbulent-boundary-layer trailing-edge noise due to design modifications. Inthis paper, an aeroacoustic method is studied, resting on a hybrid CFD/CAAprocedure. In a first step RANS simulation provides a time-averaged solution,including the mean-flow and turbulence statistics such as length-scale,time-scale and turbulence kinetic energy. Based on these, fluctuating soundsources are then stochastically generated by the Fast Random Particle-MeshMethod to simulate in a second CAA step broadband aeroacoustic sound. Fromexperimental findings it is well known that porous trailing edges significantlylower trailing edge noise level over a large range of frequencies reaching upto 8dB reduction. Furthermore, sound reduction depends on the porous materialparameters, e.g. geometry, porosity, permeability and pore size. The paperpresents first results for an extended hybrid CFD/CAA method including porousmaterials with prescribed parameters. To incorporate the effect of porosity, anextended formulation of the Acoustic Perturbation Equations with source termsis derived based on a reformulation of the volume averaged Navier-Stokesequations into perturbation form. Proper implementation of the Darcy andForchheimer terms is verified for sound propagation in homogeneous andanisotropic porous medium. Sound generation is studied for a generic symmetricNACA0012 airfoil without lift to separate secondary effects of lift and camberon sound from those of the basic edge noise treatments.

Efficient prediction of broadband trailing edge noise and application to porous edge treatment