流れ中のフィン付き円柱から発生する渦放出音に及ぼす螺旋状側板の効果

概要

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In the present paper the attention is focused on effect of helical strakes around a finned tube on Aeolian Tone. The helical strakes are mounted spirally around a twist serrated finned tube. We measured the turbulence intensity in the wake, spectrum of velocity fluctuation, the coherence of velocity fluctuations in the spanwise direction and SPL. The Aeolian tone radiated from the finned tube with helical strakes at high Reynolds number was smaller than the case of no helical strakes. The helical stakes were effective to reduce the Aeolian tone radiated from the finned tube. However, the effect of helical strakes of small diameter on vortex shedding depended on the Reynolds number. The Karman vortex was clearly formed even in the case of helical strakes of small diameter at low Reynolds number. The existence of helical strakes of small diameter around a finned tube caused the increase of the periodicity of vortex shedding from a finned tube. The coherent scale of Karman vortex in the spanwise direction was larger than that of a finned tube without helical strakes.