**DEFINITION**:

Computational methods for the numerical propagation of sound through internal and external flows. Computational predictions are most often split into noise source modelling and numerical simulation of acoustic propagation. Noise source modelling is strongly problem-dependent (turbulence, blade loads fluctuations,

cavity resonances, combustion, vibrations) and is assumed to be covered by domain 302.

Methods for the numerical propagation of sound through internal and external flows can be split into two categories, (1) integral methods and (2) discretised methods.

- Integral methods mostly used for external problems in which acoustic propagation is assumed by the analytical Green’s function in free field and uniform flow. The sound is computed at any observer point through a surface or volume integral.
- Discretized methods assume the discretisation of relevant continuous equations over the propagation medium. Flow nonhomogeneities (spatial and temporal) are taken into account from CFD results. Internal and external flows are concerned.

(Source: ACARE Domain 110)

**SUBDOMAINS:**

**Noise source modelling.****Numerical simulation of acoustic propagation**: meters, accelerometers, photogrammetry, moiré.