Comparison of computational aeroacoustics with theory using the benchmark case of sound waves excited from a semi‐infinite duct

Abstract

In this paper the benchmark problem of radiation from a semi infinite duct is discussed. The duct is modeled by an infinitesimal thin wall. Comparisons are made between the analytic solutions of R. M. Munt and the 2 nd CAA Workshop with our CAA-code. In all cases a 3D axisymmetric approach is chosen to describe the propagation of a single mode. The procedure consists of two steps.Step 1 concerns a numerical simulation of the near-field-region.Step 2 calculates the farfield-solution by means of the acoustic-analogy of Ffowcs Williams and Hawkings. Since the wall is of infinitesimal thickness, the edge needs to be treated in a special way. Two different approaches are persecuted and the results are compared.