Interaction Between Acoustic Resonance and Fluidelastic Instability in a Normal Triangular Tube Array

Abstract

The interaction between acoustic resonance and damping controlled fluidelastic instability (FEI) in a normal triangular tube array (P∕d=1.32) has been investigated. The duct acoustics were excited with speakers placed adjacent to the tube array to artificially replicate flow-induced acoustic resonance. The paper deals with the effect on the rms level of tube vibration of three independent parameters: imposed acoustic sound pressure level, freestream flow velocity, and structural damping. A fall in the FEI vibration amplitude with increasing sound pressure level in the tube array has been observed. In addition, the imposed acoustic field delays the onset of damping controlled fluidelastic instability. The effects of flow velocity and structural damping in conjunction with acoustic resonance on the rms of tube displacement are discussed. While the current study has clearly captured the phenomenon of interaction between the fluidelastic motion at approximately 10Hz and the acoustic field at approximately 1kHz, it is not apparent what the physical mechanism at work might be.