Numerical Simulation of the Flow-Sound Interaction Mechanisms of Two Side-by-Side Cylinders in Cross-Flow

A numerical simulation of the flow-excited acoustic resonance for the case of two side-by-side cylinders in cross-flow is performed. One spacing ratio between the cylinders, T/D = 1.25, is investigated, where D is the diameter of the cylinders and T is the center-to-center distance between them. The unsteady flow field is simulated using a finite-volume method at a Reynolds number of 25000. This simulation is then coupled with a finite element simulation of the resonant sound field, by means of Howe’s theory of aerodynamics sound, to reveal the details of flow-sound interaction mechanisms, including the nature and the locations of the aeroacoustic sources in the flow field. At the off resonance conditions two distinct vortex shedding frequencies are observed. These are associated with the wider and narrower wakes of the cylinders. However, when acoustic resonance is initiated the bi-stable flow phenomenon is eliminated and the vortex shedding from both cylinders occurs at a single frequency that is between those observed before the onset of acoustic resonance. Moreover, three main aeroacoustic sources are observed in the wake of the two cylinders. Two aeroacoustic sources are located just downstream of each cylinder and one aeroacoustic source is located in the gap between the cylinders. The numerical results are compared with the experimental results presented in a previous investigation and favourable agreement is obtained.