Frequency-domain prediction of sound propagation through axisymmetric flow ducts

A frequency-domain approach for computational aeroacoustics is developed for the prediction of azimuthal sound modes propagating in axisymmetric flow ducts. Different pseudo-time marching methods are implemented and compared including an upwind scheme, a four-stage Runge-Kutta scheme and a dual-time scheme. Numerical validation for hard walled ducts including simple and complex geometries are presented to evaluate the accuracy and efficiency of the proposed methods. It is shown that all the implemented time marching methods can achieve converged numerical solutions. Comparatively, the four-stage Runge-Kutta scheme is most efficient, while the upwind scheme is the most time consuming. The local time stepping technique can accelerate numerical computation to some extent. The dual-time scheme has the advantage of improving the numerical accuracy and expanding the numerical stability range.