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216 results on '"Nakakita, Kazuyuki"'

2. Time-series image denoising of pressure-sensitive paint data by projected multivariate singular spectrum analysis

Author

Ohmichi, Yuya, Takahashi, Kohmi, and Nakakita, Kazuyuki

Subjects
Electrical Engineering and Systems Science - Image and Video Processing, Computer Science - Machine Learning, Physics - Fluid Dynamics
Abstract

Time-series data, such as unsteady pressure-sensitive paint (PSP) measurement data, may contain a significant amount of random noise. Thus, in this study, we investigated a noise-reduction method that combines multivariate singular spectrum analysis (MSSA) with low-dimensional data representation. MSSA is a state-space reconstruction technique that utilizes time-delay embedding, and the low-dimensional representation is achieved by projecting data onto the singular value decomposition (SVD) basis. The noise-reduction performance of the proposed method for unsteady PSP data, i.e., the projected MSSA, is compared with that of the truncated SVD method, one of the most employed noise-reduction methods. The result shows that the projected MSSA exhibits better performance in reducing random noise than the truncated SVD method. Additionally, in contrast to that of the truncated SVD method, the performance of the projected MSSA is less sensitive to the truncation rank. Furthermore, the projected MSSA achieves denoising effectively by extracting smooth trajectories in a state space from noisy input data. Expectedly, the projected MSSA will be effective for reducing random noise in not only PSP measurement data, but also various high-dimensional time-series data.

Published
2022
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3. Stable Dynamic Mode Decomposition Algorithm for Noisy Pressure-Sensitive Paint Measurement Data

Author

Ohmichi, Yuya, Sugioka, Yosuke, and Nakakita, Kazuyuki

Subjects
Computer Science - Machine Learning, Mathematics - Dynamical Systems, Physics - Fluid Dynamics
Abstract

In this study, we investigated the stability of dynamic mode decomposition (DMD) algorithms to noisy data. To achieve a stable DMD algorithm, we applied the truncated total least squares (T-TLS) regression and optimal truncation level selection to the TLS DMD algorithm. By adding truncation regularization to the TLS DMD algorithm, T-TLS DMD improves the stability of the computation while maintaining the accuracy of TLS DMD. The effectiveness of the T-TLS DMD was evaluated by the analysis of the wake behind a cylinder and practical pressure-sensitive paint (PSP) data for the buffet cell phenomenon. The results showed the importance of regularization in the DMD algorithm. With respect to the eigenvalues, T-TLS DMD was less affected by noise, and accurate eigenvalues could be obtained stably, whereas the eigenvalues of TLS and subspace DMD varied greatly due to noise. It was also observed that the eigenvalues of the standard and exact DMD had the problem of shifting to the damping side, as reported in previous studies. With respect to eigenvectors, T-TLS and exact DMD captured the characteristic flow patterns clearly even in the presence of noise, whereas TLS and subspace DMD were not able to capture them clearly due to noise., Comment: 8 pages, 7 figures

Published
2021
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7. Dual-luminophore pressure-sensitive paint measurement using three-gate lifetime method with photodegradation correction.

Author

Uchida, Kazuki, Nakakita, Kazuyuki, Sugioka, Yosuke, Asai, Keisuke, and Nonomura, Taku

Subjects
*PRESSURE-sensitive paint, *JET impingement, *PRESSURE measurement, *LUMINOPHORES
Abstract

In this paper, we propose a photodegradation correction method for the dual-luminophore pressure-sensitive paint (PSP) measurement using lifetime-based imaging, which was proposed for correction of the temperature-induced error but has suffered from photodegradation in the previous studies. We introduced a parameter that characterizes the photodegradation of a dual-luminophore PSP as the intensity ratio between the two luminophores. The changes in the calibration coefficients for the pressure and the temperature due to photodegradation were corrected based on this parameter. In this study, a coupon-based calibration test was performed, and the luminescence characteristics of the dual-luminophore PSP including photodegradation were investigated. Then, the proposed method was applied to a coupon-based validation test and a jet impingement test, and the effectiveness of the method was evaluated by comparing results with and without correction. The pressure measurement accuracy was significantly improved by photodegradation correction. [ABSTRACT FROM AUTHOR]

Published
2024
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17. パネルディスカッション 「我が国の航空科学技術における 数値シミュレーション・ビジョン策定を目指して」

Author

TAKAHASHI, Takashi, HASHIMOTO, Atsushi, MITSUO, Kazunori, and NAKAKITA, Kazuyuki

Abstract

流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム2020オンライン (2020年9月28日-30日. 日本航空宇宙学会 : 宇宙航空研究開発機構(JAXA)オンライン会議), Fluid Dynamics Conference / Aerospace Numerical Simulation Symposium 2020 Online (September 28-30, 2020. The Japan Society for Aeronautical and Space Sciences : Japan Aerospace Exploration Agency (JAXA), Online meeting), 海外では、NASAの『CFD Vision 2030』など、長期的なビジョンが策定されており、我が国においても数値解析技術に関するビジョン・方策の策定が期待されている。2019年度のJAXA航空技術部門の主務大臣評価結果において、「数値シミュレーション技術レベルを国際比較で高い水準に保つための長期的な方策を示すことを望む。」と指摘されたことも受けて、航空技術部門長の諮問委員会として「数値シミュレーション技術に関する外部有識者委員会」（以下、諮問委員会）を立ち上げ、40年後の2060年、及び20年後の2040年時点での航空科学技術における我が国の数値シミュレーション・ビジョン、並びにそれを達成するための具体的な方策の策定を行うこととなった。 本パネルディスカッションでは、これまで本委員会において議論されてきた内容を共有するとともに、パネリストである委員と参加者との間で有意義な議論を交わすことによって、より洗練されたビジョン・方策の策定に繋げる場として企画された。, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2030013001, レポート番号: JAXA-SP-20-008

Published
2021

22. Research on Prediction Technology of Water Spray Generated from Aircraft Tire

Author

Kubota, Kenichi, Koga, Seigo, Iijima, Yoshimi, Koike, Shunsuke, and Nakakita, Kazuyuki

Abstract

第51回流体力学講演会/第37回航空宇宙数値シミュレーション技術シンポジウム (2019年7月1日-3日. 早稲田大学早稲田キャンパス国際会議場), 新宿区, 東京, 51st Fluid Dynamics Conference / the 37th Aerospace Numerical Simulation Symposium (July 1-3, 2019. International Conference Center, Waseda University), Shinjuku-ku, Tokyo, Japan, Research on prediction technology of water spray generated from aircraft tires is going on in JAXA. As a prediction tool, a numerical code using the explicit MPS (Moving Particle Simulation) method, which is one of the particle methods, is being developed to simulate the water spray. As a benchmark problem, the water spray test conducted by NASA was simulated under a simplified condition. It was found that the angle of side spray observed behind the tire is consistent with the experimental data when the deformation of the tire due to load is taken into account, whereas the angle was underestimated when the deformation was ignored. Experimental efforts to obtain in-house data are also being made to validate the simulation. A laboratory model has been fabricated to establish the technology to measure the water behavior, and a test using actual tire is also planned in the near future., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1930011019, レポート番号: JAXA-SP-19-007

Published
2020

27. Development of the Magnetic Pulse Compression Circuit for DBD-PA（ Dielectric-Barrier-Discharge Plasma-Actuator） and the Application for Dynamic Stall control

Author

Suzuki, Kento, Komuro, Atsushi, Kanno, Shouki, Koike, Motomi, Nankai, Kouki, Takashima, Keisuke, Yasuda, Hidemasa, Ochi, Akio, Hayama, Kenji, Tsujiuchi, Tomoka, Nakakita, Kazuyuki, Mitsuo, Kazunori, Nonomura, Taku, Kaneko, Toshiro, Ando, Akira, and Asai, Keisuke

Subjects
磁気パルス圧縮回路, ダイナミックストール, プラズマアクチュエータ, ナノ秒パルス放電
Abstract

形態: 図版あり, Physical characteristics: Original contains illustrations, Accepted: 2018-12-15, 資料番号: PA1920036000

Published
2019

31. Experimental Study of Slat Noise from 30P30N Three-Element High-Lift Airfoil in JAXA Hard-Wall Low-Speed Wind Tunnel

Author

Murayama, Mitsuhiro, Nakakita, Kazuyuki, Yamamoto, Kazuomi, Ura, Hiroki, Ito, Yasushi, and Choudhari, Meelan M

Subjects
Aerodynamics
Abstract

Aeroacoustic measurements associated with noise radiation from the leading edge slat of the canonical, unswept 30P30N three-element high-lift airfoil configuration have been obtained in a 2 m x 2 m hard-wall wind tunnel at the Japan Aerospace Exploration Agency (JAXA). Performed as part of a collaborative effort on airframe noise between JAXA and the National Aeronautics and Space Administration (NASA), the model geometry and majority of instrumentation details are identical to a NASA model with the exception of a larger span. For an angle of attack up to 10 degrees, the mean surface Cp distributions agree well with free-air computational fluid dynamics predictions corresponding to a corrected angle of attack. After employing suitable acoustic treatment for the brackets and end-wall effects, an approximately 2D noise source map is obtained from microphone array measurements, thus supporting the feasibility of generating a measurement database that can be used for comparison with free-air numerical simulations. Both surface pressure spectra obtained via KuliteTM transducers and the acoustic spectra derived from microphone array measurements display a mixture of a broad band component and narrow-band peaks (NBPs), both of which are most intense at the lower angles of attack and become progressively weaker as the angle of attack is increased. The NBPs exhibit a substantially higher spanwise coherence in comparison to the broadband portion of the spectrum and, hence, confirm the trends observed in previous numerical simulations. Somewhat surprisingly, measurements show that the presence of trip dots between the stagnation point and slat cusp enhances the NBP levels rather than mitigating them as found in a previous experiment.

Published
2014

32. Effect of Vortex Generators on Three-Dimensional Wings in Transonic Flows

Author

Koike, Shunsuke, Ito, Yasushi, Kusunose, Kazuhiro, Murayama, Mitsuhiro, Nakakita, Kazuyuki, and Yamamoto, Kazuomi

Subjects
Streamwise vortex, NASA Common Research Model, Vortex generator, Transonic buffet, Shock wave boundary layer interaction
Abstract

本報告書は, 2011年から2015年にかけJAXAで実施した遷音速バフェット抑制のためのVortex Generator (VG)に関する研究結果をまとめたものである. 既報「遷音速二次元翼に対するVortex Generator効果」の続編にあたる. 既報では, 後退角のない2次元翼に限定し, VGの効果をまとめた. 本報告書では, 実機を模擬した遷音速3次元翼に対するVGの効果をまとめた. 研究は, 風洞実験とComputational Fluid Dynamics(CFD)の双方を用いて行った. 風洞実験においてもCFDにおいても, 航空機形状のNASA Common Research Model (NASA CRM) の主翼を対象とした. VGについては, 矩形形状, かつ, 全てのVGの導入する縦渦の向きが等しいVG列(Co-rotating VGs)を対象とした. 本報告書を実用的な報告書にするという観点から, まず, 本研究から導かれたVGの設計指針とVGの効果に対する仮説を含む原理を示した. その上で, 風洞実験およびCFDにより調べたVGの基本的なパラメータ, 高さ, 長さ, 角度, 間隔のVGの効果に対する感度をそれぞれまとめた. 解析手法については, 風洞実験およびCFDの比較から, 本研究で行ったCFD解析は定性的にはVGの効果を適切に捉えられることが明らかとなった. VGの効果に関する新たな知見を得るために, 既報で調査した後退角のない2次元翼模型と本研究の3次元翼の結果を比較した. さらにCFDにより複数の後退角の無限後退翼について, VGの効果を調べた. その結果, 後退角のある3次元翼においては, VGの導入する縦渦の回転方向が極めて重要であること, VGの前縁が翼端を向くVG 配置 (Toe-Out VGs) が剥離抑制に効果が高いことが明らかとなった. 約30度の後退角をもつNASA CRMの主翼に対してToe-Out VGsを使用する場合は, VGの間隔をVGの高さの80倍としても, VGの効果が明瞭に現れた. この間隔は, 後退角のない2次元翼模型の場合の8倍の間隔である. VGの間隔を広くとれることはVGの設置枚数を減らすことにつながり, VGの巡航時の付加抵抗の低減につながる. 後退角のある3次元翼に対しては, VGの向きをToe-Outに取り, VG の間隔を後退角の大きさを考慮して設計することが極めて重要であることを明らかにした., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1730025000, レポート番号: JAXA-RR-17-013

Published
2018

33. Summary of Second Aerodynamics Prediction Workshop (APC-II)

Author

Hashimoto, Atsushi, Aoyama, Takashi, Matsuo, Yuichi, Ueno, Makoto, Nakakita, Kazuyuki, Hamamoto, Shigeru, Sawada, Keisuke, Matsushima, Kisa, Imamura, Taro, Ochi, Akio, and Yoshimoto, Minoru

Subjects
Aerodynamics, CFD, Workshop
Abstract

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2017-07-18, 資料番号: PA1820015000

Published
2018

34. Summary of First Aerodynamics Prediction Workshop (APC-I)

Author

Hashimoto, Atsushi, Aoyama, Takashi, Matsuo, Yuichi, Ueno, Makoto, Nakakita, Kazuyuki, Hamamoto, Shigeru, Sawada, Keisuke, Matsushima, Kisa, Imamura, Taro, Ochi, Akio, and Yoshimoto, Minoru

Subjects
Aerodynamics, CFD, Workshop
Abstract

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2017-07-18, 資料番号: PA1820014000

Published
2018

35. Temperature correction of pressure-sensitive paint for industrial wind tunnel testing

Author

Kurita, Mitsuru, Nakakita, Kazuyuki, Mitsuo, Kazunori, and Watanabe, Shigeya

Subjects
Wind tunnel models -- Materials, Pressure -- Measurement, Pressure -- Methods, Aerospace and defense industries, Business, Science and technology
Abstract

Pressure-sensitive paint measurement can obtain a much more detailed surface pressure distribution than can be obtained using conventional pressure taps. However, the pressure-sensitive paint is sensitive not only to pressure but also to temperature, and where high accuracy is required, it is essential to compensate for this temperature dependency. This paper discusses data processing methods for pressure-sensitive paint measurement in transonic industrial wind tunnel testing, and proposes three methods to compensate for temperature dependency of the pressure-sensitive paint: an in situ method, an a priori method, and a hybrid of a priori and in situ methods. The pressure distributions from the pressure-sensitive paint data obtained by these proposed methods are compared with pressure tap data measured by conventional pressure transducers, and it is confirmed that the proposed methods are effective in compensating the temperature dependency of pressure-sensitive paint and improve the accuracy of the obtained data. It is also found that the hybrid of a priori and in situ methods is widely applicable to the industrial wind tunnel testing even if the pressure range of the pressure tap data is limited.

Published
2006

36. 非定常空力現象兆候検出へのデータマイニング試行

Author

Chiba, Kazuhisa, Watanabe, Shinya, Nakata, Masaya, Umeda, Yuhei, Hamada, Naoki, Yasue, Kanako, Suzuki, Koji, Kuchiishi, Shigeru, Nakakita, Kazuyuki, and Ito, Takeshi

Subjects
Transonic buffet, Sign detection, Airplane, Unsteady aerodynamic data, Data mining
Abstract

第49回流体力学講演会/第35回航空宇宙数値シミュレーション技術シンポジウム (2017年6月28日-30日. 国際オリンピック記念青少年総合センター), 渋谷区, 東京, 49th Fluid Dynamics Conference /the 35th Aerospace Numerical Simulation Symposium (June 28-30, 2017. National Olympics Memorial Youth Center), Shibuya-ku, Tokyo, Japan, The transonic buffet degrades the aerodynamic performance of the aircraft during cruise. It is a phenomenon that should be avoided absolutely as it may lead to accidents. However, the mechanism of occurrence has yet to be elucidated. To understand this phenomenon, large-scale unsteady data is accumulated using computational fluid dynamics. In contrast, data mining of time series data such as unsteady data is a recent topic in that field. In this study, we have attempted to perform unsteady data mining with capacity exceeding Tera’s order. As a result, the behavior of the physical quantity before the transonic buffet arises was suggested to be different from the data just before the transonic buffet occurs. Moreover, a topological data analysis revealed abnormalities before the temporal origination determined by visualizing flow structure. Based on the results, we visualized the data over time, and found the characteristic change of the viscosity distribution on the wing surface. This should be a clue to elucidate this phenomenon., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1730011020, レポート番号: JAXA-SP-17-004

Published
2017

38. Dynamic Stall Control around Practical Airfoil Using Nanosecond-Pulse-Driven Dielectric Barrier Discharge Plasma Actuators

Author

Iwasaki, Yuto, primary, Nonomura, Taku, additional, Nankai, Koki, additional, Asai, Keisuke, additional, Kanno, Shoki, additional, Suzuki, Kento, additional, Komuro, Atsushi, additional, Ando, Akira, additional, Takashima, Keisuke, additional, Kaneko, Toshiro, additional, Yasuda, Hidemasa, additional, Hayama, Kenji, additional, Tsujiuchi, Tomoka, additional, Nakajima, Tsutomu, additional, and Nakakita, Kazuyuki, additional

Published
2020
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44. Evaluation of Sprayable Unsteady PSP for Application in a Transonic Wind Tunnel

Author

Sugioka, Yosuke, Numata, Daiju, Asai, Keisuke, Koike, Shunsuke, Nakakita, Kazuyuki, and Koga, Seigo

Subjects
Pressure-Sensitive Paint, Unsteady measurement, Transonic flow
Abstract

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: PA1720029000

Published
2016

45. 遷音速流れ場における非定常圧力計測のための感圧塗料技術の現状

Author

Sugioka, Yousuke, Numata, Daiju, Asai, Keisuke, Nakakita, Kazuyuki, Koike, Shunsuke, and Nakajima, Tsutomu

Abstract

Second Aerodynamics Prediction Challenge (APC-II) ワークショップ (2016年7月6日. 金沢歌劇座), 金沢市, 石川, 注記: 第48回流体力学講演会/第34回航空宇宙数値シミュレーション技術シンポジウム内で実施, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630028013, レポート番号: JAXA-SP-16-004

Published
2016

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