多翼ファンから発生する広帯域騒音に及ぼすカルマン渦列の影響(流体工学,流体機械)

概要

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In the prediction theory for the broadband noise generated from a multi-blade fan, the vortices in the Karman vortex street was divided into n pieces. The local lift produced by the multiple vortices was substituted for the sound pressure of the fan noise. The frequency distribution of the noise was estimated so that the Strouhal number could become constant even if the wake is spread by the diffusion. From the results of the measurement of the internal flow of the fan, it was found that the noise was related to the wake characteristics of the specific location in the scroll casing where the relative velocity was high. The noise operating in the vicinity of the maximum efficiency point of the fan was distributed over the domain from 500Hz to 1250Hz. The sound pressure within the frequency domain was in proportion to the sixth power of the flow rate coefficient, and it was inversely proportional to the second power of the frequency. It was experimentally proved that the influence of the Karman vortex street on the noise in the domains of high and low frequencies did not exist when the distribution of the estimated sound pressure level corresponded to the measured broadband noise.
一般社団法人日本機械学会の論文
2005-11-25