Aeroacoustics can be regarded as the acoustic discipline where sound is generated by an aerodynamic turbulent field in a moving medium. In aeroacoustics, coupling exists between the aerodynamic and the acoustic field. Examples of aeroacoustic sound sources in the environmental acoustic field are the noise of airplane jet engines and the noise generated in ventilation ducts. Another application is the exhaust pipe system of road vehicles. The exhaust gases that flow through the pipe system generates sound in the pipe, the mufflers and in the free jet behind the tailpipe. The exhaust jet behind the tailpipe refracts the radiated sound waves. Also, energy conversion from the acoustic field to the aerodynamic field (the vortex street of the shear layer) occurs.
Sound radiation from a tailpipe in a hot jet.
In the EXPLICA project, the radiated sound from the tailpipe in the presence of the exhaust jet flow and in the presence of an automotive body and road has been investigated numerically. The computational approach is an hybrid computational aero acoustic (CAA) approach, where the aerodynamic field is separated from the sound propagation model (paper J09). The main focus of the research has been on the modeling of the sound propagation by advanced computational methods. In particular, the discontinuous Galerkin method and pseudospectral methods are utilised (papers C19 and C21). The final results of the project can be found in paper J21.