1 0 0 0 前方流速場nudgeによる衝撃波変調~波面消失原理実証と応用展開
本研究では、衝撃波面前方に僅かな流速場を誘起すること(流速場nudge)によって波面を消失させるくらい積極的に背後圧力の増加を抑制する方法を原理実証し、ソニックブームなどの衝撃波被害緩和に応用することを目的とする。主要実験装置として「流動衝撃波管」を開発し、既設の屋内自由空間も活用して実験サイトを整備し、数値解析と光学可視化計測と密接にタイアップして研究を推進する。流速変化領域の有限長さや多次元性の影響等も含めて、関連する流体力学現象を解明し、衝撃波緩和・消失デバイスを原理実証、機能評価し、応用展開につなげる。
1 0 0 0 OA 多翼送風機の翼間の流れ構造と発生音に関する実験的研究
- 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
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.