Numerical Simulation of the Sound Generation and the Sound Propagation from Air Intakes in an Aircraft Cabin

Abstract

The paper presents results of unsteady Reynolds-averaged Navier-Stokes simulations (URANS), Delayed Detached Eddy Simulations (DDES) and Large Eddy Simulations (LES) of the flow and the noise propagation in a segment of the DLR's cabin test facility Do728. Since the weakly compressible Navier-Stokes equations were solved in all cases, spectra of the sound pressure levels (SPL) were analyzed based on Fast Fourier Transforms of the predicted pressure fields. It was shown that LES on hexahedral meshes predict SPLs in good agreement with microphone measurements in the Do728 cabin. A comparison with predictions based on a hybrid approach involving the solution of a wave equation together with non-reflective boundary conditions on the one hand, and a Ffowcs Williams-Hawkings (FW-H) model on the other hand, revealed that the impact of the imperfect acoustic boundary condition in the LES on the sound pressure level at the receiver point is negligible. Thus, it was demonstrated that reliable predictions of SPLs in an aircraft cabin are possible if the corresponding LES can be performed.