FINITE-DIFFERENCE SOLUTIONS TO SOUND RADIATION FROM CYLINDRICAL DUCTS

A numerical analysis is developed for sound radiation from cylindrical ducts. The structure of the radiated field is numerically obtained fo r unflanged, flanged, and horned-type ducts, including the effect of m ean flow field. The governing equation for acoustic disturbances is a linearized unsteady Euler equation about a steady compressible mean fl ow. The numerical simulation is conducted by a fourth-order accurate f inite difference scheme. The present result for the reflection coeffic ient shows good agreement with the experiment and available theory. Th e results also show that a nonuniform mean flow reduces the sound pres sure level, although this is not valid for a uniform mean flow.