Abstract
The effect of spiral fin around a bare tube on aerodynamic noise was experimentally investigated. This fin was made from a thin plate and mounted spirally around a bare tube surface. We measured the intensity of velocity fluctuation, the spectrum of velocity fluctuation, the coherence distribution in the spanwise direction and the spectra of sound pressure level of noises. As a result it was made clear that the periodic velocity fluctuation caused by Karman vortex was observed in the wake of the fin tube although the fin mounted around a bare tube. The large scale vortices in the spanwise direction were formed in the wake of the fin tube. Aeolian tone induced by Karman vortex shedding was observed in the case of fin tube. However, as the pitch of the fins decreased, the peak levels of spectra of sound pressure level decreased.
