Theoretical prediction of sound propagation in an annular duct

Abstract

In this paper, sound propagation in an annular duct with shear mean flow is studied using the Galerkin method. A simple polynomial which satisfies the boundary conditions is selected as the basis funciton. It not only can be used in the calculation of an annular duct, but also can be used for circular ducts. The refraction effect due to shear mean flow is observed in upstream and downstream propagation. It is more apparent in the upstream case. The sound attenuation due to acoustic liners is investigated and the optimum liner which causes the maximum attenuation is also demonstrated. ft Sm ' x*(tf®íiT^umMmmmmz¥¿m > msm&fSMcmzntimïï