A combined time and frequency domain approach for acoustic resonance prediction

A general hybrid time- and frequency-domain methodology has been developed to identify acoustic resonance conditions of internal flow configurations. The acoustic modes are determined by imposing onto the flow a time-dependent excitation at several locations on the boundary. The resulting time-domain pressure responses, which are computed via an unsteady Favre-Reynolds averaged Navier-Stokes solver, are used to determine the frequency response function matrix of the fluid which can be considered to be a multiple-input multiple-output system. The main test case was selected to be a closed-end cylindrical duct for which the effect of different excitation techniques on the predicted acoustic modes is discussed in detail. The last test case deals with the acoustic characterization of a 2-D channel with symmetric bumps and an inlet flow velocity of 17 m s- 1. It is shown that the methodology was suitable for identifying axial and transverse acoustic modes up to 3 kHz. 2007 Elsevier Ltd. All rights reserved.