Radiation of Sound From a Point Source in a Short Duct

It is the purpose of this paper to provide, in relatively brief form, a summary of a boundary integral approach that has been developed for calculating the sound field radiated from short ducts in uniform axial motion. The method was devised primarily to study sound generated by rotating sources in the duct, as is of current practical interest in connection with ducted-fan aircraft engines. Detailed background on the fan source application of the technique can be found. The author has not previously discussed the simpler monopole source case of interest in these proceedings. However, readers desiring a more detailed treatment than will be included here should have little difficulty in extracting it from those references after making the relatively minor modifications necessary to adapt the analyses to the monopole case. It should be noted that other authors have also considered radiation from short ducts. In particular, readers may find the finite-element approach of Eversman of interest as well as the alternate boundary integral method treatments of Martinez and of Dunn, Tweed, and Farassat.