Aspects of numerically solving Euler's equations for aeroacoustic problems

Kurzfassung

The main topic of the presentation is the discussion of various numerical difficulties associated with solving Euler's equations numerically in order to compute aerodynamic noise. This concerns not only the sound propagation though generally moving media, but -even more important- also the simulation of the very noise generation. Considering modern high order, dispersion relation preserving numerical schemes for the unsteady Euler equations (CAA methods) as potential means of computing, say the interaction of vorticity with geometric inhomogeneities, and thus the noise generation directly, also implies certain fundamental difficulties. These arise, unavoidably by e.g. introducing artificial selective damping into the numerical representation of the equations. But also other potential pitfalls in an Euler simulation of a noise generation process are discussed as well as possible work-arounds. The presentation shows examples of "artificial noise generation" and "physical noise generation", both computed numerically by solving Euler's equations. an attempt is made to estimate the "signal to (numerical) noise ratio" in an acoustic simulation.