Use of linearized Euler equations for subsonic flow noise prediction

Abstract

The introduction of efficient numerical techniques like Tam’s DRP scheme allows one to develop aeroacoustic modeling based on Euler equation solvers and applied on realistic configurations. It is already clear that the system of Euler equations is the most complete one in order to compute acoustic propagation in fluids, but the way to calculate noise generation with the same equations needs to be established. So, it is necessary to introduce in the propagation calculation some information coming from a previous or a simultaneous flow calculation. One approach is to try to define source terms for the Euler equations as it was set up for Lighthill’s or Lilley’s equation. Others approaches can rely on the coupling of the two equation systems by domain decomposition or by introducing disturbances linked to flow calculation. The SNGR model belongs to the first category. A source term is defined by analogy with Lilley’s equation. A stochastic space time turbulent field is used in order to avoid expensive LES or DNS flow computations. This approach is mainly applied to the calculation of noise radiated by internal flows where the methods based on the classical acoustic analogy do not work easily.