Hybrid computational aeroacoustics approach based on the synthetic turbulence model in Eulerian description

A low-cost hybrid computational aeroacoustics (CAA) approach based on the synthetic turbulence and acoustic perturbation equations (APE) is established. A statistic model based on Reynolds Averaged Navier-Stokes (RANS) simulation is introduced to generate the unsteady synthetic turbulence. The spatial correlation of the turbulence is realized via the spatial filtering of a white noise field. Instead of using the Lagrangian convective particles of the fast random particle-mesh (fRPM) method, the presented model is entirely established in Eulerian description by introducing a convection-attenuation equation of the synthesized turbulent velocity. Therefore, the same discretization is applied for both synthetic turbulence model and APE solver. Without the requirement of the interpolation between different discretization systems, this modified model is more concise to implement numerically and more accessible to extend to parallel processing. Since the convection-attenuation equation only operates in the sound source domain, additional boundary conditions are established. The recommended parameters for mesh generation are discussed through a validation case. The hybrid CAA approach based on the presented model is applied to the slat noise prediction of a two-dimensional high-lift airfoil. Good agreement is found through the comparison with the reference data, and the computational costs are acceptable.