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In the present paper the attention is focused on the relation between vortex shedding phenomena andacoustic resonance which occurred in the two-dimensional model of boiler.There were tube bankswith in-line arrangement for small tube pitch ratio.We measured the sound pressure level,the phasedelay of acoustic pressures,the spectrum of velocity fluctuation and the gap velocity.As a result, wefound two peak frequencies of sound pressure level with different Strouhal numbers S_t,mainly about0.26 and 0.52.The noise of S_t=0.26 was the resonance of transverse mode and S_t=0.52 waslongitudinal mode.The vortex shedding of S_t=0.15 was generated inside the tube banks withoutacoustic resonance. As gap velocity increased, we observed that the peak level of spectrum was weakand broad-banded. The onset velocity of the acoustic resonance of longitudinal mode was lower thanthat of transverse mode.
In the present paper the attention is focused on the relation between vortex shedding phenomena andacoustic resonance which occurred in the two-dimensional model of boiler.There were tube banks with in-line arrangement for small tube pitch ratio. We measured the sound pressure level, the phasedelay of acoustic pressures, the spectrum of velocity fluctuation and the gap velocity. As a result, wefound two peak frequencies of sound pressure level with different Strouhal numbers S_t, mainly about0.26 and 0.52.The noise of S_t = 0.26 was the resonance of transverse mode and S_t = 0.52 was longitudinal mode. The vortex shedding of S_t = 0.15 was generated inside the tube banks withoutacoustic resonance. As gap velocity increased, we observed that the peak level of spectrum was weakand broad- banded. The onset velocity of the acoustic resonance of longitudinal mode was lower thanthat of transverse mode.