Flow induced acoustical resonance in exhaust gas economizer tube arrays

Staggered arrays of closely packed rigid tubes have been tested, in a wind tunnel of varying the flow velocity, to investigate the conditions under which acoustical resonances do or do not occur. Among the aspects which have been investigated are the Stouhal numbers at which flow periodicities occur; the relation between these Stouhal numbers and those at which acoustical resonances occur; the effect of the Reynolds numbers and the longitudinal tube spacing on the occurrence of acoustical resonance. This investigation has shown that: 1) The acoustical resonance can be produced at a frequency well removed from that of vortex shedding. The results also show evidence of both phenomena existing, simultaneously at different frequencies. 2) The acoustical resonances behaviour is consistent with that of a self excited system. 3) An alternative model of this phenomenon provides a better procedure for avoiding these resonances in closely packed tube banks.