研究者詳細 - 坪井　伸幸

論文 - 坪井　伸幸

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Numerical simulation on ignition with shock tube - Effect of reflected shock wave - Boundary layer at adiabatic wall interaction on ignition 査読有り

Asahara M., Machida T., Yamada E., Hayashi A., Tsuboi N.

Science and Technology of Energetic Materials 75 ( 1-2 ) 50 - 58 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

A reflected shock wave in two-dimensional shock tube is studied numerically using Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. The results reproduced mild and strong ignition behind the reflected shock wave, in particular, the detailed mild ignition process, which was not shown well in past research. Owing to the interaction between the viscous boundary layer and the reflected shock wave, the latter has a lambda shock configuration. The flow behind the lambda shock wave becomes a complex vortical structure ; thus, the reactive gas mixture flowing along the detached vortices reaches high temperature and pressure because of compression at the tube side walls. The chemical reaction starts at the location that reaches the auto-ignition temperature to create flame kernels. The above history is appropriate for the process in which a flame kernel appears at the location between the triple point of the lambda shock wave and the tube wall but is insufficient for the process in which a flame kernel appears near the tube center, which is above the triple point of the lambda shock wave.

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84904443456&origin=inward

Numerical simulation on H<inf>2</inf>-O<inf>2</inf> detonation induced by direct initiation near detonation limits 査読有り

Asahara M., Hayashi A., Tsuboi N.

Science and Technology of Energetic Materials 75 ( 3-4 ) 99 - 105 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

In order to prevent an accidental explosion by detonation it is necessary to clarify detonation limit and to comprehend its ignition condition. In the past experimental studies were performed to understand critical initiation energy and critical energy density and to propose detonation limit by initiation energy and energy density. However extracting dominant parameters for detonation continuation is difficult because various experimental conditions to compare for detonation continuation are not definitely consistent Therefore these parameters will be put in order by numerically analyzing 2D direct initiation of detonation in oxyhydrogen mixture assuming ideal ignition conditions, and will be clarified for detonation limits. As a result it is found that there exist the conditions for detonation and explosion. These conditions are organized to obtain a detonation limit curve which is quite similar curve shown by Watt and Sharpe. The obtained detonation limit curve is found to be a function of a radius and pressure of initial source region and to give a prediction of the critical source energy for detonation with those initial conditions Additionally a local explosion is predicted near the x-axis boundary under a quasi-steady state condition because of a disturbance there and this type of local explosion was observed by Bach et aL.

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84916939418&origin=inward

An analysis of the quantum effect on the thermodynamic and transport properties of cryogenic hydrogen using molecular dynamics method 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Hayashi A., Tokumasu T.

Journal of Physics: Conference Series 490 ( 1 ) 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

In this paper, we have analysed an effect of quantum nature of the hydrogen molecule on its thermodynamic and transport properties using molecular dynamics (MD) method based on the path integral method. We performed NVE constant MD simulation and the quantum effect on the molecular mechanism was analysed. The simulation results were compared with experimental data. As a result, we clarified that the quantum nature makes the virial pressure larger than in classical mechanics and taking account the quantum nature makes smaller intermolecular interaction energy and larger repulsive force than classical representation. Besides, we have confirmed that the path-integral-based MD method well reproduces the thermal conductivity and quantum effect on the transport properties is also large. © Published under licence by IOP Publishing Ltd.

DOI： 10.1088/1742-6596/490/1/012160

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84896979582&origin=inward

A molecular dynamics study of nuclear quantum effect on the diffusion of hydrogen in condensed phase 査読有り

Nagashima H., Tsuda S., Tsuboi N., Koshi M., Hayashie A., Tokumasu T.

AIP Conference Proceedings 1618 950 - 953 2014年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2014 AIP Publishing LLC.In this paper, the quantum effect of hydrogen molecule on its diffusivity is analyzed using Molecular Dynamics (MD) method. The path integral centroid MD (CMD) method is applied for the reproduction method of time evolution of the molecules. The diffusion coefficient of liquid hydrogen is calculated using the Green-Kubo method. The simulation is performed at wide temperature region and the temperature dependence of the quantum effect of hydrogen molecule is addressed. The calculation results are compared with those of classical MD results. As a result, it is confirmed that the diffusivity of hydrogen molecule is changed depending on temperature by the quantum effect. It is clarified that this result can be explained that the dominant factor by quantum effect on the diffusivity of hydrogen changes from the swollening the potential to the shallowing the potential well around 30 K. Moreover, it is found that this tendency is related to the temperature dependency of the ratio of the quantum kinetic energy and classical kinetic energy.

DOI： 10.1063/1.4897890

Scopus

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84947543854&origin=inward

Numerical Study of Real Gas Effects on Shock Tube Problems at Supercritical Conditions 査読有り

MUTO Daiki, TSUBOI Nobuyuki, TERASHIMA Hiroshi

TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN ( 一般社団法人日本航空宇宙学会 ) 12 ( 29 ) Po_2_39 - Po_2_44 2014年01月

記述言語：英語掲載種別：研究論文（学術雑誌）

Investigations of real gas effects of supercritical fluids on shock tube problems were numerically performed. Understandings of fluid behaviors under supercritical conditions are essential for the design of high pressure combustors. We developed a numerical code for simulations of flow fields under the supercritical conditions. Cubic types of equation of state are applied to evaluate properties of nearcritical and supercritical fluids. The present code was tested on shock tube problems, and the present result agreed well with a reference result. Comparisons of results between the real gas equations of state and the ideal gas equation of state showed differences in position of shock waves, contact discontinuities, and expansion fans due to the specific thermodynamic features of the supercritical fluids. In a condition that crosses the critical point, the results showed a large density jump with a small temperature jump at the contact discontinuity because of drastic changes of thermodynamic properties. This indicated that the real gas effects obviously appear when the initial condition is close to the critical point of the working fluids.

DOI： 10.2322/tastj.12.Po_2_39

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130004956821

J0550204 分子動力学法による液体水素の輸送物性に対する量子効果の影響解析([J055-02]マイクロ・ナノスケール熱流体現象(2))

永島浩樹, 津田伸一, 坪井伸幸, 越光男, 林光一, 徳増崇

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _J0550204 - -_J0550204- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we conducted analysis of quantum effect of hydrogen molecules on the energy transport of liquid hydrogen using classical Molecular Dynamics (MD) and path integral Centroid MD (CMD) method. We performed MD simulation across a wide temperature region in the constant density and compared the thermal conductivity of each method. The thermal conductivity was calculated using non-equilibrium MD method. As a result, it was confirmed that CMD shows lower thermal conductivity than classical MD and this tendency is consistent with experimental data. Moreover, it was clarified that because of the change of intermolecular potential due to the quantum effect, the potential energy transport by molecular motion and the energy transport by intermolecular interaction decrease.

DOI： 10.1299/jsmemecj.2014._J0550204-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943927

J0550104 分子動力学シミュレーションによる臨界点近傍のニ原子分子流体に対する密度ゆらぎの評価([J055-01]マイクロ・ナノスケール熱流体現象(1))

井川祥平, 徳増崇, 坪井伸幸, 津田伸一

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _J0550104 - -_J0550104- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we investigated the density fluctuation of diatomic fluids around the critical points for evaluation of the principle of corresponding state. We used Molecular Dynamics (MD) simulation against the 2-Center Lennard-Jones (2CLJ) fluids for extraction of structure of fluctuation around the critical points. We evaluated the density fluctuation by two methods. One is the dispersion of number of molecules at certain domain as time-averaged quantity. The other is the calculation of static structure factor. As the results, in 2CLJ fluids that have shorter molecular elongations comparatively, the principle of corresponding state is satisfied because of the small difference in the fluctuation structure extracted by the present two methods.

DOI： 10.1299/jsmemecj.2014._J0550104-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943922

G0510306 3次元数値解析による高圧水素噴流の管内における自着火機構の解明([G051-03]流体工学部門一般セッション(3),流体工学部門)

横山瑛紀, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510306 - -_G0510306- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

One of self-ignition mechanisms of high-pressure hydrogen jet occurs by vortex caused from instability. Several studies about self-ignition of high-pressure hydrogen spouted from a tube attached with a tank are reported. In this analysis, the numerical study is performed to find out mechanism of self-ignition of hydrogen jet in a tube with a 10mm in diameter connected to a high pressure tank of 9.0MPa. Hydrogen and air are mixed at their contact surface to yield vortices, and the mixture ignites because the high temperature and high pressure regions are yielded behind the precursor shock wave.

DOI： 10.1299/jsmemecj.2014._G0510306-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943304

G0510305 反射衝撃波と境界層の干渉による流れの3次元挙動に関する数値解析([G051-03]流体工学部門一般セッション(3),流体工学部門)

若林諒, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510305 - -_G0510305- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

At the reflected shock rear, a chemical reaction starts at a temperature and pressure constant static premixed gas conditions by filling reactive premixed gas in the shock tube, and reflects the shock wave in the pipe ends. Meyer and Oppenheim were classified into ignition two forms Mild Ignition and Strong Ignition, the start of the H2/O2 detonation due to the reflected shock wave. In order to ignite instantly in the tube cross-section of the entire near-wall reflection, Strong Ignition is a form ignition reaction theory. Mild Ignition is a firing mode hydrodynamic, under the influence of lambda shock wave generated by the mutual interference between the boundary layer and are reaching the ignition shock wave backward flow becomes multidimensional. Mark was revealed from the experiment due to the mutual interference between the boundary layer and the reflected shock, lambda shock wave to be formed in connection with this phenomenon. Thus, experiments by the reflected shock ignition is performed, there are cases in which ignition occurs is unexpected due to the interference of the reflected shock wave and boundary layer. In this study, we focus on the flow field due to the interference of the boundary layer and reflected shock, it is an object of the present invention to elucidate the flow three-dimensional.

DOI： 10.1299/jsmemecj.2014._G0510305-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943303

G0510304 矩形管内を伝播するデトネーション波の多頭構造に関する3次元数値解析([G051-03]流体工学部門一般セッション(3),流体工学部門)

朝原誠, 長尾剛史, 坪井伸幸, 林光一

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510304 - -_G0510304- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

Three-dimensional numerical analysis using practical scale of the experiment is performed to obtain cellular structure in rectangular tube. As a result, transverse wave in three-dimensions moves in different direction comparing with two-dimensional structure at the point of propagation structure. Furthermore, each transverse wave affects to accelerate the propagation velocity in circumferential direction and makes unreacted gas pockets after transverse wave goes through each other.

DOI： 10.1299/jsmemecj.2014._G0510304-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943302

G0510303 数値解析によるローテーティングデトネーションエンジンの推力性能に関する研究([G051-03]流体工学部門一般セッション(3),流体工学部門)

吉田航, 朝原誠, 坪井伸幸

年次大会 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _G0510303 - -_G0510303- 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

Study of detonation engine has been actively carried out in order to improve the thrust performance and expected to apply rocket engine. Even among them, rotating detonation engine has attracted attention. Many experiments have been performed, but in the experiments, varying the combustion chamber size is difficult. In this study, the numerical study is carried out to find out thrust performance with changing combustion chamber size.

DOI： 10.1299/jsmemecj.2014._G0510303-

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009943301

806 ローテーティングデトネーションエンジンの運転条件と性能評価 : 格子解像度がIspに与える影響

渡辺裕介, 坪井伸幸, 原野孝也, 小島孝之, 林光一

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _806 - 1_-_806-2_ 2014年01月

802 超臨界圧力下における極低温同軸噴流への噴射器形状の及ぼす効果に関する数値解析

武藤大貴, 坪井伸幸, 寺島洋史

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _802 - 1_-_802-2_ 2014年01月

B213 分子動力学シミュレーションによる二原子分子流体の臨界点近傍における密度ゆらぎに関する研究

井川祥平, 徳増崇, 坪井伸幸, 永島浩樹, 津田伸一

熱工学コンファレンス講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _B213 - 1_-_B213-2_ 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

In this study, we evaluated the density fluctuation of diatomic fluids around the critical point. We performed Molecular Dynamics (MD) simulation against 2-Center-Lenard-Jones (2CLJ) fluids that have molecular elongation as a parameter. We compared the density fluctuation of each fluid to evaluate the principle of corresponding state of density fluctuation. We evaluated the density fluctuation by dispersion of number of molecules, static structure factor, and intermediate scattering function. As the results, in 2CLJ fluids that have shorter molecular elongation comparatively, the principle of corresponding state of static fluctuation structure was satisfied.

DOI： 10.1299/jsmeted.2014._B213-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009938965

811 ハイブリッドロケット内部の3次元非定常圧縮性流れの数値解析 : 乱流モデルによる影響

坂本まい, 武藤大貴, 坪井伸幸

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _811 - 1_-_811-2_ 2014年01月

808 数値解析によるエアロスパイクノズルの性能評価 : 内部ノズルの性能評価

芝尾将史, 坪井伸幸, 伊藤隆

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _808 - 1_-_808-2_ 2014年01月

804 Waverider形状の熱的影響に関する数値解析

浦優介, 衞藤遥, 坪井伸幸, 丸祐介, 藤田和央

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _804 - 1_-_804-2_ 2014年01月

523 固体高分子形燃料電池触媒層一次細孔内の酸素輸送挙動に関する分子動力学的解析

出口将嗣, 福島啓悟, 坪井伸幸, 徳増崇

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _523 - 1_-_523-2_ 2014年01月

219 極超音速流れにおけるランプ模型周りの場数値解析 : ランプ角度の影響

黒川久仁彦, 坪井伸幸, 倉本健史

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _219 - 1_-_219-2_ 2014年01月

1404 H_2/O_2混合気中における衝撃波収束による着火の機構に関する数値解析

朝原誠, 三谷奈々, 坪井伸幸

流体工学部門講演会講演論文集 ( 一般社団法人日本機械学会 ) 2014 ( 0 ) _1404 - 1_-_1404-2_ 2014年01月

記述言語：日本語掲載種別：研究論文（研究会，シンポジウム資料等）

A reflected shock wave by focusing reflector is simulated using the Navier-Stokes equations with the detailed oxy-hydrogen reaction mechanism. Into the tube which has focusing end wall, ignition successes around focal point under the no-ignition condition at the flat wall. The shock focusing is one of effective way of detonation initiation. However, the ignition mechanism from shock focusing is not clear. In this study, we aim to indicate the ignition phenomena induced by shock focusing.

DOI： 10.1299/jsmefed.2014._1404-1_

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009938781

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