Acoustic resonance in a staggered tube array: Tube response and the effect of baffles

Abstract

An experimental laboratory study was performed to measure the effect of acoustic noise on the magnitude of tube vibrations in a staggered tube array and to measure the effectiveness of baffles on suppressing transverse duct modes. The acoustically induced tube vibration was experimentally determined for a flexible tube in three different transverse locations in the tube array. It was found that a tube located in the center of the duct, where a nodal point of the acoustic pressure resided, was most influenced by the transverse mode. On the other hand, a tube located near the duct side wall, where the acoustic pressure oscillation was highest, was not affected by the acoustic standing wave since it produced almost imperceptible vibration. It is shown that the acoustic pressure gradient across a tube is the cause of the tube vibration. Experiments were also performed to determine the effect of baffles for reducing the noise of acoustic resonance. The results showed that a single baffle substantially reduced the first mode resonance, as long as it was located close to the center of the bundle. The insertion of two baffles, in various locations, effectively eliminated acoustic resonance in the 1st and 2nd transverse duct modes. It is seen that the third acoustic mode is not significantly affected by either one or two baffles.