著者

飯田 明由 岩崎 正志 水野 明哲

出版者

日本流体力学会

雑誌

ながれ : 日本流体力学会誌 (ISSN:02863154)

巻号頁・発行日

vol.25, no.6, pp.543-551, 2006-12-25

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鳥人間用滑空機の設計製作はものづくり教育のひとつとして効果的であるが,事前に飛行テストを行うことが難しいこと,設計要素が多岐にわたることなどから設計の最適化が難しいという問題があった.本研究では,鳥人間用滑空機の設計の最適化を図るため,滑空機の三次元飛翔解析プログラムと遺伝的アルゴリズムを用いた最適化手法について検討した.主翼,尾翼の寸法,機体長さなどの8つの設計変数と飛び出し時の速度や飛び出し角度を遺伝情報化し,飛行距離を目的関数として遺伝的アルゴリズムを用いて解析を行った.各世代の個体数を200とし,50世代にわたり解析を行い,飛翔性能に強く関係する優性遺伝子を抽出した.解析によって得られた結果を用いて外乱に強い機体の設計を行い,コンテストで確実に飛行する機体を提案した.提案されたモデルは2005年度の鳥人間コンテストで4位に入賞,審査員特別賞を受賞し,遺伝的アルゴリズムによる最適化の有効性を確認した.

著者

飯田 明由 小久保 あゆみ 塚本 裕一 本田 拓 横山 博史 貴島 敬 加藤 千幸

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 B編 (ISSN:03875016)

巻号頁・発行日

vol.73, no.732, pp.1637-1646, 2007-08-25 (Released:2011-03-03)

参考文献数

10

被引用文献数

4 1 7

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The aim of this investigation is to understand the generation mechanism of aero-acoustic feedback noise radiated from rear-view mirrors. In order to clarify the relationship between the velocity fluctuation and radiated noise, correlation in terms of aerodynamic noise and velocity fluctuations were measured in a low-noise wind tunnel. The experimental results showed that noise level of the tonal-noise depended on the ratio of the height of the bump to the thickness of the boundary layer. Strong tonal-noise was generated when the height of the bump was almost equal to 40% of the height of the boundary layer. The tonal-noise level also depended on the length between the trailing-edge of the bump and the edge of rear-view mirror. The frequency of the tonal noise can be calculated by modified Rossiter equation. The tonal-noise was disappeared in the case of the bump was placed at separated boundary layer. It revealed that the seed of the tonal noise was small disturbances generated by the bump on the surface of the rear-view mirror.

著者

内田 孝紀 小野 謙二 飯田 明由 吉村 忍 加藤 千幸 山出 吉伸 今村 博 植田 祐子

出版者

一般社団法人 日本風力エネルギー学会

雑誌

風力エネルギー学会 論文集 (ISSN:24363952)

巻号頁・発行日

vol.45, no.4, pp.71-82, 2021 (Released:2022-03-30)

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In the current project, the first author and the second author play a central role in conducting high-speed tuning and wind turbine wake analysis of the supercomputer version of RIAM-COMPACT. In this report, we applied the supercomputer version RIAM-COMPACT to the wind turbine wake simulation from the wind tunnel scale to the utility-scale wind turbine wakes. As a result, we clarified unsteady wake aerodynamics of wind turbines including multiple wake interactions with high precision and high reality.

著者

荻野 琢己 飯田 明由 大田 浩嗣 杉田 光弘

出版者

一般社団法人 日本機械学会

雑誌

流体工学部門講演会講演論文集 2019 (ISSN:24242896)

巻号頁・発行日

pp.IS-29, 2019 (Released:2020-07-25)

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The aim of this investigation is to estimate drag force acting on a bicycle helmet and power required for wind speed of bicycle race. It is known that a helmet of bicycle race has not only role to protect the head but also reduce aerodynamic drag force. Since the required power of caused by aerodynamic force acting on the helmet and head is about 18% of the total power of cycling, development of the low drag force helmet is required. To evaluate and understand the unsteady aerodynamic force and its generation mechanism, LES analysis was performed. As a result, the streamlined shape helmet placed in straight against the flow has low drag, but the drag force rapidly increases in the posture during goal sprinting. Therefore, the power required for top speed of bicycle race is more than three times that in steady state. Since, the flow around the helmet is unsteady, the maximum fluid force reaches 3.5 times that of the average. For this reason, it is required to develop robust shape helmet against changes in posture with small fluctuating drag force.

著者

横山 博史 北宮 克哉 飯田 明由

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B編 (ISSN:18848346)

巻号頁・発行日

vol.79, no.804, pp.1419-1433, 2013 (Released:2013-08-25)

参考文献数

16

被引用文献数

1 1

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To clarify the mechanism of acoustic radiation in flows around a cascade of flat plates, fluid structures and acoustic fields were elucidated by direct simulations. The simulations were mainly performed for flows around 5 parallel plates and the separation-to-thickness ratio s/d was 6.0. The freestream velocity was changed from 30 m/sec to 60 m/sec, and the acoustic resonance occurs between plates at the freestream velocity of 44 m/sec. At that velocity, the Reynolds number based on the chord length and the freestream velocity was 8.7×104 and that based on the plate thickness was 5.8×103. Computational results were validated by the experimental results performed in the present research. The computational results showed that large-scale vortices composed of fine-scale vortices are shed in the wakes of the plates independently of the acoustic resonance. When the large-scale vortex is shed from the upper or lower face, an expansion wave is radiated around the downstream edge of the upper or lower face, respectively. The compression wave is radiated around the downstream edge of the opposite face. The simulation for the flow around a single plate was also performed, and the results confirmed the above-mentioned acoustic radiation mechanism. For the flows around a cascade of flat plates, the sheddings of the vortices from neighboring plates are synchronized when the acoustic resonance occurs. It was also clarified that the mode of the synchronization is an anti-phase mode and the standing waves generated between plates are reinforced.

著者

飯田 明由 岩崎 正志 水野 明哲

出版者

社団法人 日本流体力学会

雑誌

日本流体力学会誌「ながれ」 (ISSN:02863154)

巻号頁・発行日

vol.25, no.6, pp.543-551, 2006-12-25 (Released:2010-10-22)

参考文献数

7

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鳥人間用滑空機の設計製作はものづくり教育のひとつとして効果的であるが, 事前に飛行テストを行うことが難しいこと, 設計要素が多岐にわたることなどから設計の最適化が難しいという問題があった. 本研究では, 鳥人間用滑空機の設計の最適化を図るため, 滑空機の三次元飛翔解析プログラムと遺伝的アルゴリズムを用いた最適化手法について検討した. 主翼, 尾翼の寸法, 機体長さなどの8つの設計変数と飛び出し時の速度や飛び出し角度を遺伝情報化し, 飛行距離を目的関数として遺伝的アルゴリズムを用いて解析を行った. 各世代の個体数を200とし, 50世代にわたり解析を行い, 飛翔性能に強く関係する優性遺伝子を抽出した. 解析によって得られた結果を用いて外乱に強い機体の設計を行い, コンテストで確実に飛行する機体を提案した.提案されたモデルは2005年度の鳥人間コンテストで4位に入賞, 審査員特別賞を受賞し, 遺伝的アルゴリズムによる最適化の有効性を確認した.

著者

水野 明哲 飯田 明由 福留 桂子

出版者

一般社団法人 日本機械学会

雑誌

年次大会講演論文集 2004.2 (ISSN:24331325)

巻号頁・発行日

pp.145-146, 2004-09-04 (Released:2017-08-01)

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In order to improve the aerodynamic performance of vertical axis wind turbines (VAWT), effects of pitch angle of rotor blades were numerically investigated. To solve the complicated turbulent flow field around moving airfoils with small computers, discreet vortex methods were utilized. The numerical result shows that the pitch angle is important factor to improve the aerodynamic performance. In the case of pitch angle is 1 degree, an angle of attack becomes small at upwind position of the rotor blade, and therefore, flow separation is restrained at upwind part of the VAWT. As a result, the power coefficient is 10 % larger than that of the conventional (pitch angel is 0 degree) VAWT.

著者

達 晃一 篠原 直秀 金 勲 鍵 直樹 坂口 淳 飯田 明由 山内 康 安原 幸生 坪倉 誠 内藤 航

出版者

公益社団法人 自動車技術会

雑誌

自動車技術会論文集 (ISSN:02878321)

巻号頁・発行日

vol.52, no.5, pp.1013-1020, 2021 (Released:2021-08-16)

参考文献数

10

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本研究では、① ウイルスの感染対策を講じる上で必要な現象(換気や飛沫・飛沫核の挙動や表面汚染など)について、実測・実験室実験・シミュレーションを組み合わせて明らかにすること、② 場ごとの経路別リスク評価を行い、場ごとに対策によるリスク低減効果を推定すること、③ 飛沫核に対する対策技術の開発を行うことを目的とする.今回の報告では、①路線バスの換気実態調査結果および③エアロゾルフィルタ(本研究では粒子捕集のフィルタをエアロゾルフィルタと呼ぶこととする)の効果について報告する.

著者

飯田 明由 岩崎 正志 水野 明哲 Iida Akiyoshi Iwasaki Masashi Mizuno Akisato

出版者

宇宙航空研究開発機構

雑誌

宇宙航空研究開発機構特別資料: 境界層遷移の解明と制御研究会講演論文集 第37回・第38回 = JAXA Special Publication: Proceedings of the 37th and 38th JAXA Workshops on Investigation and Control of Boundary-Layer Transition (ISSN:1349113X)

巻号頁・発行日

vol.JAXA-SP-06-013, pp.43-46, 2007-02-23

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Nowadays, the flight distance of champion team of the birdman rally contest was over 400 m. In order to break the record, we have to consider the weather conditions, flight conditions and design optimization of the glider. For this purpose, we developed the three-dimensional flight simulator and the optimization program based on genetic algorithm. The simulation result of the three-dimensional flight simulator was reasonably agreement with the real flight. GA (Genetic Algorithm) optimization was carried out with two hundreds samples and fifty generations. The dominant genes of airplane for the contest were obtained with GA. The performance map showed the optimal airplanes such as the champion team were sensitive and not easy-handle. The simulator was suggested another optimized model with flexible wing that was not sensitive to flight conditions. The proposed model got the fourth prize and the referee's award of the birdman rally contest 2005.

著者

田所 真樹 横山 博史 水野 雅隆 飯田 明由 若松 幹生 Phan Vinh Long 田中 博

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.84, no.863, pp.18-00199, 2018 (Released:2018-07-25)

参考文献数

19

被引用文献数

2

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Aerodynamic noise generated around a step such as front pillars of automobiles, which is transmitted into the cabin through the window glass, can negatively affect the comfort of the passengers. For the reduction of this noise, it is necessary to clarify the acoustic source and process of the propagation of the acoustic waves from the step. To do this, direct aeroacoustic simulations were performed along with wind tunnel experiments for flows around a forward step in a turbulent boundary layer, where the freestream Mach number was 0.1 and the Reynolds number based on the incoming boundary layer thickness, δ, and the freestream velocity was 2.73×104. The computations were performed for the height of h/δ = 0.9 and 3.4, where the effects of the step height on the radiated sound were investigated. The radiated sound becomes more intense for the higher step of h/δ = 3.4 particularly in a low frequency range of St ≤ 1.5, where St is the non-dimensional frequency based on the step height and freestream velocity, due to the occurrence of the large-scale vortices in the separated flow. To elucidate the radiation of the acoustic waves, the pressure fluctuations were decomposed into non-radiating convective and radiating acoustic components by usage of two methods. One is utilizing wavenumber-frequency spectra and the other one is spatial Gaussian filtering for the fluctuations at each frequency, which is proposed in this paper. The results by the former method present that the level of convective components is larger than the acoustic components by 20 - 40 dB. Moreover, the radiating components by the proposed spatial filtering method show that the radiation occurs around the step edge and the reattachment point. It is indicated that the proposed method is effective for the investigation of the acoustic radiation for the pressure fluctuations composed of convective and acoustic components.

著者

宮本 孟宜 横山 博史 飯田 明由

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.84, no.861, pp.18-00121-18-00121, 2018 (Released:2018-05-25)

参考文献数

19

被引用文献数

1

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Intense sound is radiated due to aeroacoustic feedback loop from a flow around the trailing edge of a curved plate with a kink shape such as a bonnet of an automobile. For the reduction of this noise, the control by a plasma actuator (PA) was investigated. The aim of this investigation is to clarify the effects of flow control by the PA on noise reduction and the noise reduction mechanism. To do this, wind tunnel experiments with a half-scale bonnet model and direct numerical simulations of flow and sound fields were performed. The investigation of the effects of the position for the installation of the PA on the control presents that the control at the position close to the flow separation point around the kink is effective for the noise reduction. Also, the control effects were compared between co-flow and counter-flow configurations regarding the direction of the mean induced flow by the actuator to the freestream. The mean velocity profiles showed that the flow separation was suppressed by the control with both configurations, while this control effect is more effective for the counter-flow configuration. The measured velocity fluctuations present that the power in broadband frequency range in the downstream of the actuator becomes larger by the control with both configurations. The predicted results show that small-scale vortices are shed near the wall around the actuator due to the large counter-flow induced flow. This introduction of the vortices and the intensification of the broadband velocity fluctuations lead to the suppression of the flow separation. Also, the development of the power of the velocity fluctuations at the fundamental frequency of the baseline tonal sound is weakened by the suppression of the flow separation. This supports the predicted results of the suppression of the two-dimensional vortices contributing to the acoustic radiation around the re-attachment point by the control. Consequently, the control can lead to the suppression of the feedback loop of the radiating mechanism of tonal sound.

著者

蒔田 秀治 飯田 明由

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.55, no.515, pp.1847-1854, 1989-07-25

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The local similarity hypothesis was verified in quasi-isotropic turbulent flow fields with turbulence Reynolds numbers of over 3000. The quasi-equilibrium range was known to exist in a turbulence field with turbulence Reynolds numbers of Re_τ >60. The lowest wave number of the quasi-equilibrium range in the energy spectrum was dependent on T_L/T_O : the ratio between the time scale of decay of turbulence energy and the characteristic time scale o an energy-containing eddy. Turbulent eddies with characteristic time scales of less than T_L/4 were statistically stable. The energy dissipation rate was theoretically determined as ε=C_1(q^2/2)^<3/2>/l_O, and the scales of turbulence were estimated from C_1 and Re_λ.

著者

飯田 明由 水野 明哲 金野 祥久

出版者

豊橋技術科学大学

雑誌

基盤研究(C)

巻号頁・発行日

2007

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トンボの飛翔を模擬した羽ばたき型MAVを開発し, 羽ばたき翼周りの流れと発生する流体力の関係を定量的に明らかにした. また, ヘリウムガスを用いてMAVの機体重量を調整することにより, 世界で始めて自由飛翔中のMAV周りの流れの非定常計測を行い, 自由飛翔中のトンボとMAV周りの流れが相似であることを定量的に示した.

著者

飯田 明由 小久保 あゆみ 塚本 裕一 本田 拓 横山 博史 貴島 敬 加藤 千幸

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.73, no.732, pp.1637-1646, 2007-08-25

被引用文献数

6

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The aim of this investigation is to understand the generation mechanism of aero-acoustic feedback noise radiated from rear-view mirrors. In order to clarify the relationship between the velocity fluctuation and radiated noise, correlation in terms of aerodynamic noise and velocity fluctuations were measured in a low-noise wind tunnel. The experimental results showed that noise level of the tonal-noise depended on the ratio of the height of the bump to the thickness of the boundary layer. Strong tonal-noise was generated when the height of the bump was almost equal to 40% of the height of the boundary layer. The tonal-noise level also depended on the length between the trailing-edge of the bump and the edge of rear-view mirror. The frequency of the tonal noise can be calculated by modified Rossiter equation. The tonal-noise was disappeared in the case of the bump was placed at separated boundary layer. It revealed that the seed of the tonal noise was small disturbances generated by the bump on the surface of the rear-view mirror.

著者

岩崎 正志 飯田 明由 水野 明哲

出版者

一般社団法人日本機械学会

雑誌

流体工学部門講演会講演論文集 (ISSN:13482882)

巻号頁・発行日

vol.2005, 2005-10-28

著者

飯田 明由 足立 節子 朴 聖煥

出版者

公益社団法人日本工学教育協会

雑誌

工学・工業教育研究講演会講演論文集

巻号頁・発行日

vol.19, pp.160-161, 2007-08-02