The scientific field of aeroacoustics deals with the interaction between a background mean flow and an acoustic field propagating in this flow. In general, this concerns both the very complex description of the creation of sound by turbulence in the background flow, that is, flow induced noise and the influence the background mean flow has on the propagation of an externally created sound field, that is, flow borne noise or flow borne sound. The computational aeroacoustics (CAA) capabilities of the aeroacoustics interfaces in COMSOL Multiphysics only cover the flow borne noise/sound situation.

Aeroacoustic simulations would ideally involve solving the fully compressible continuity, momentum (Navier-Stokes equations), and energy equations in the time domain. The acoustic pressure waves would then form a subset of the fluid solution. This approach is often impractical for real-world computational aeroacoustics (CAA) applications due to the required computational time and memory resources. Instead, for solving many practical engineering problems, a decoupled two-step approach is used: first solve for the fluid flow, then the acoustic perturbations of the flow.

is the sum of the background mean pressure p0 and the acoustic pressure variations p (sometimes labeled p’ or p1).