著者

高橋 護 岩野 耕治 酒井 康彦 伊藤 靖仁

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.850, pp.17-00004-17-00004, 2017 (Released:2017-06-25)

参考文献数

26

被引用文献数

1

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Simultaneous measurement of the velocity-gradient and fluctuating static pressure was carried out in a turbulent planar jet. We use a constant-temperature hot-wire anemometry and a miniature pressure probe for velocity measurement and fluctuating static pressure measurement, respectively. Two types of the combined probe are introduced for simultaneous measurement of the velocity-gradient and fluctuating static pressure. One consists of an X-type hot-wire probe and a pressure probe and the other consists of two I-type hot-wire probes arranged in vertical direction and a pressure probe. For improvement of the measurement accuracy, the responsivity of the pressure probe, the time-lag due to the spatial distance between the hot-wire probe and the pressure probe, and the attenuation of the velocity-gradient measurement due to the finite difference method, are corrected. In this paper, we compare the various statistics of the turbulent planar jet acquired using the combined probes and those acquired using hot-wire probe or pressure probe alone. Through the results, it is confirmed that the simultaneous measurements were well-performed in the turbulent planar jet expect for the outside of the velocity half-width. Further, it is revealed that the Pressure Rate-of-Strain Correlation, which appears in the Reynolds stress transport equation, is almost dominated by (p´/ρ)(∂u´2/∂x1) and (p´/ρ)(∂u´1/∂x2) barely contributes to the Reynolds stress transport in the cases of Re ≥ 10,000.

著者

岩野 耕治 後藤 優典 深尾 勇也 酒井 康彦 伊藤 靖仁 長田 孝二 酒井 雅晴 落合 利徳 小田 修三

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.849, pp.16-00541-16-00541, 2017 (Released:2017-05-25)

参考文献数

10

被引用文献数

2

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The relationship between flow structure and generation of aerodynamic sound from a multi-blade fan is experimentally investigated with enlarged two-dimensional blade models. Two blade models with different shapes are used. Sound pressure level and blade surface pressure are measured simultaneously where the sound transmittable board is used to find the position of sound source. In addition, flow velocity and blade surface pressure are also measured simultaneously. The results show that the sound pressure level takes highest values near the reattachment point of the flow on blade suction surface, where the RMS value of the surface pressure fluctuation takes highest value, and where coherence between the sound pressure and surface pressure takes high values. These values vary with the shape of blades. The size of separation bubble and the intensity of velocity fluctuation also differ by the shape of the blades. The large scale vortical flow structures are extracted by conditional averaging for blade surface pressure fluctuations. Sizes of the large scale vortices correspond to the peak frequencies of the blade surface pressure fluctuation and frequency characteristic of surface pressure fluctuation is explained by the convections of the vortices. In addition, the sizes of large scale vortices correspond to the size of separation bubble. This fact suggests that making separation bubble smaller is an efficient way for reduction of aerodynamic noise of a multi-blade fan.