LAUSR

Normal mode radiation properties of ducts issuing a subsonic mean flow have been thoroughly investigated in the past. The behavior of the radiation characteristics, such as the magnitude of the reflection coefficient and the length correction, are well understood. Nevertheless, the behavior of the same features in the presence of an incoming low Mach number flow has not been investigated in detail, particularly in the case of the length correction. This work presents a numerical study of the reflection coefficient and length correction of unflanged pipes and pipes terminated by circular horns of different radii in the presence of an incoming flow. The investigations are conducted with a tridimensional lattice Boltzmann scheme. The results suggest that the detachment and reattachment of the incoming flow inside the duct play a significant role on the transfer of kinetic energy from the flow to the internal acoustic field. Moreover, the results show that the mechanism of flow detachment and reattachment is ...