The discipline of acoustics, which is a study of pressure waves in fluids, is intimately related to fluid dynamics. Many sounds that are technologically important in industrial applications are generated by and propagated in fluid flows. The phenomena associated with sounds can therefore be understood and analyzed in the general framework of fluid dynamics. The governing equations for acoustics are indeed the same as the ones governing fluid flows.
The main challenge in numerically predicting sound waves stems from the well-recognized fact that sounds have much lower energy than fluid flows, typically by several orders of magnitude. This poses a great challenge to the computation of sounds in terms of difficulty of numerically resolving sound waves, especially when one is interested in predicting sound propagation to the far field. Another challenge comes from the difficulty of predicting the very flow phenomena (e.g., turbulence) in the near field that are responsible for generating sounds.
This chapter provides an overview of FLUENT's approaches to computing aerodynamically generated sound, the underlying theories, the model setup, and the procedure for computing sound.