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1 0 0 0 OA Aerodynamics of Owl-like Wing Model at Low Reynolds Numbers

著者: Hikaru AONO Katsutoshi KONDO Taku NONOMURA Masayuki ANYOJI Akira OYAMA Kozo FUJII Makoto YAMAMOTO
出版者: THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
雑誌: TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES (ISSN:05493811)
巻号頁・発行日: vol.63, no.1, pp.8-17, 2020 (Released:2020-01-04)
参考文献数: 63
被引用文献数: 7

Aerodynamics of an owl-like wing model at low Reynolds numbers (Re = O(104–5)) are investigated using large-eddy simulations with high-resolution computational schemes. The airfoil shape of the owl-like wing model is constructed based on a cross-sectional geometry of the owl wing at 40% wingspan from the root. The chord-based Re ranges from 1.0 × 104 to 5.0 × 104 and the angle of attack (α) varies from 0 to 14 deg. The time-averaged lift (Cl) and drag coefficients computed are in reasonable agreement with the results of force measurement. The results computed clarify a nonlinear change in the Cl curve slope, which is due to an increase in the suction peaks in conjunction with the change in type of separation, the formation of a laminar separation bubble (LSB), and pressure recovery on the pressure side. The generation of the LSB on the suction and/or pressure sides at the Re of 2.3 × 104 and 4.6 × 104 are seen, while reattachments are observed only on the pressure side at the Re of 1.0 × 104 due to the camber of the wing. Furthermore, the owl-like wing model demonstrates favorable aerodynamic performance in terms of a maximum lift-to-drag ratio in comparison with several airfoils at the Re range considered. This is due to the strong suction peaks and distribution of surface pressure on the pressure side. It is emphasized that the concave lower surface enhances the time-averaged aerodynamic performance at all of the α even though the LSB is generated and fluctuation in lift history is induced at low α.

2020-01-10 09:34:31
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1 0 0 0 OA 片頭痛と中枢性過眠症

著者: 鈴木圭輔
出版者: 日本神経治療学会
雑誌: 神経治療学 (ISSN:09168443)
巻号頁・発行日: vol.35, no.6, pp.S124, 2018 (Released:2018-11-12)

2020-01-10 09:15:40
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1 0 0 0 OA カオス, 周期点, エントロピー : 一次元力学系のエルゴード理論

著者: 高橋陽一郎
出版者: 一般社団法人日本物理学会
雑誌: 日本物理学会誌 (ISSN:00290181)
巻号頁・発行日: vol.35, no.2, pp.149-161, 1980-02-05 (Released:2008-04-14)
参考文献数: 21

微分方程式は, 古典力学と共に誕生した. その対象はケプラーの法則のような「秩序」であると信じられてきた. しかし, 微分方程式は自然現象を忠実に描写する, 極めて良い道具であり, 例えば, 乱流をも記述してしまっていた. さらに, 差分方程式は複雑で微分方程式は単純であるという神話も, 自由度1, 2の世界のものであり, 統計力学のレジームに入る, 乱流のようなカオティックな現象も自由度有限の世界で既に現れている自然な現象である. ここでは, 最も簡単な一次元変換について, 統計力学的な定式化に向けての, 数学的, 即ち, 愚直な試みを述べる.