Duct Effects on Acoustic Source Radiation

This paper presents a detailed numerical investigation of the effects of a semi-infinite hard-walled duct on the radiation due to point dipole sources rotating around the duct axis. In particular, this study is concerned with the effect of source position relative to the duct open end and its comparison with radiation in a free field. This study was motivated by the increasing tendency of ducted propellers and fans to be located close to the open end, relative to the acoustic wavelength. In this study, the conditions under which duct effects on source radiation may be neglected are established.