Simultaneous Finite Element Computation of Direct and Diffracted Flow Noise in Domains with Static and Moving Walls

Curle’s acoustic analogy allows one to compute aerodynamic noise due to flow motion in the presence of rigid bodies. However, the strength of the dipolar term in the analogy depends on the values of the total flow pressure on the body’s surface. At low Mach numbers, that pressure cannot be obtained from the computational fluid dynamics (CFD) simulation of an incompressible flow, because the acoustic component cannot be captured. To circumvent this problem, and still being able to separate the flow and body noise contributions at a far-field point, an alternative approach was recently proposed which does not rely on an integral formulation. Rather, the acoustic pressure is split into incident and diffracted components giving rise to two differential acoustic problems that are solved together with the flow dynamics, in a single finite element computational run. In this work, we will revisit the acoustics of that approach and show how it can be extended to predict the flow noise generated in domains with moving walls.