遠心羽根車の後流と円柱との干渉によって発生する離散周波数騒音に関する研究 : 第2 報干渉騒音の予測

概要

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In the first report, in order to clarify the influence of the cutoff of the scroll casing on the discrete frequency noise, the dependence of the diameter of a cylinder on the discrete frequency noise generated from interaction with the wake of a centrifugal impeller was discussed. From results of the analysis on the interaction noise and flow around the cylinder, a several experimental characteristics have been obtained. In the second report, in order to predict the interaction noise generated from a centrifugal fan, the prediction theory of the noise level based on the wake characteristics of the centrifugal impeller is proposed. In the prediction theory, the drag in the wake of the centrifugal impeller is applied for the periodic fluctuation phenomenon of the momentum on the solid surface of the cylinder. The noise level of the predicted value was able to estimate quantitatively decrease of the interaction noise by the diffusion of the wake.