Shear Layer Instability in the Gap of Tandem Cylinders and Its Coupling With Higher Order Acoustic Modes

Abstract This paper presents an experimental investigation of the aeroacoustic response from tandem cylinders in cross flow at different positions with respect to the acoustic particle velocity nodes and anti-nodes of different cross-modes. The objective is to better understand the role of the shear layer instability in the gap between the cylinders on the excitation of acoustic resonance and its coupling with higher-order acoustic modes. The results show that the tandem cylinders’ position with respect to the acoustic particle velocity anti-nodes of the cross-modes is a significant factor in determining the excitation of the dominant acoustic mode. Moreover, placing multiple rows of tandem cylinders at various positions with respect to the acoustic standing waves of the cross-modes in the duct promotes the coupling between the shear layer instability and the acoustic modes, even for the cases that didn’t trigger such excitation when the tandem cylinders were placed in a single row.