長津　雄一郎NAGATSU Yuichiroナガツ　ユウイチロウ

業績情報

氏名・連絡先

• 氏名

  ナガツ　ユウイチロウ, 長津　雄一郎, NAGATSU Yuichiro

• 生年

  1975

• eメールアドレス

  nagatsucc.tuat.ac.jp

• 個人ホームページ

  http://www.tuat.ac.jp/~nagatsu/

主たる所属・職名

• 工学研究院　応用化学部門, 教授

その他の所属

• 工学部　化学システム工学科
• 工学府　応用化学専攻

経歴

• -
  日本学術振興会特別研究員（DC2）
  自 2002年04月01日, 至 2003年09月30日
• -
  名古屋工業大学大学院 工学研究科 物質工学専攻 助教（助手）
  自 2003年10月01日, 至 2011年12月15日
• -
  日本学術振興会 海外特別研究員（受入研究者：ベルギー、ブリュッセル自由大学、Anne De Wit教授）
  自 2008年04月01日, 至 2009年09月29日
• -
  東京農工大学大学院 工学研究院 応用化学部門　准教授
  自 2011年12月16日
• -
  JSTさきがけ研究者（「エネルギー高効率利用と相界面」領域）
  自 2013年10月01日, 至 2017年03月31日

学歴

• 慶應義塾大学
  理工学部
  機械工学科
  至 1998年03月, 卒業
• 慶應義塾大学
  理工学研究科
  至 2000年03月, 修了, 博士前期
• 慶應義塾大学
  理工学研究科
  至 2003年09月, 単位取得満期退学, 博士後期

学位

• 博士（工学）
  慶應義塾大学
  2005年03月

研究分野

• A689　ものづくり技術（機械・電気電子・化学工学）, A19010　流体工学
• A689　ものづくり技術（機械・電気電子・化学工学）, A27010　移動現象、単位操作

研究キーワード

• 反応流、反応輸送現象

研究テーマ

• 反応流、反応輸送現象
  自 9999

担当授業科目

• 移動現象論および演習
  2020年
• 化学プロセス数学
  2020年
• 物質機能設計特論I
  2020年
• 物質機能設計特論II
  2020年
• 化学物理工学実験I
  2020年
• 化学物理工学概論
  2020年
• 化学システム工学演習
  2020年
• 化学システム工学実験III
  2020年
• BASE概論
  2020年
• 化学物理工学基礎プロジェクト演習
  2020年
• 移動現象論および演習
  2019年
• 化学プロセス数学
  2019年
• 化学システム工学実験III
  2019年
• 移動現象論
  2018年
• 化学プロセス数学
  2018年
• 化学システム工学実験III
  2018年
• 分子情報工学特論Ⅰ
  2017年
• 移動現象論および演習
  2017年
• 化学プロセス数学
  2017年
• 化学システム工学実験Ⅲ
  2017年
• 基礎プロジェクト演習
  2017年
• 分子情報工学特論Ⅱ
  2017年
• 応用化学セミナーⅣ
  2017年
• 特別計画研究
  2017年
• 応用化学セミナーⅡ
  2017年
• 応用化学特別実験
  2017年
• 応用化学特別研究
  2017年
• Chemical Reaction Engineering
  2017年
• 分子情報工学特論Ⅱ
  2016年
• Chemical Reaction Engineering
  2016年
• 特別計画研究
  2016年
• 応用化学セミナーⅢ
  2016年
• 化学プロセス数学
  2016年
• 化学システム工学実験Ⅲ
  2016年
• 応用化学セミナーⅠ
  2016年
• 応用化学セミナーⅡ
  2016年
• 応用化学特別実験
  2016年
• 応用化学特別研究
  2016年
• 化学システム工学演習
  2016年
• 移動現象論および演習
  2016年
• 応用化学セミナーⅡ
  2015年
• 応用化学特別実験
  2015年
• 応用化学特別研究
  2015年
• インターンシップⅠ
  2015年
• 分子情報工学特論Ⅰ
  2015年
• 化学プロセス数学
  2015年
• システム工学概論
  2015年
• 化学工学基礎演習Ⅰ
  2015年
• 化学システム工学実験Ⅲ
  2015年
• Chemical Reaction Engineering
  2015年
• 特別計画研究
  2015年
• 化学システム工学演習
  2014年
• システム工学概論
  2014年
• 化学プロセス数学
  2014年
• Chemical Reaction Engineering
  2014年
• 化学工学基礎演習Ⅰ
  2014年
• 応用化学セミナーⅡ
  2014年
• 応用化学特別実験
  2014年
• 応用化学特別研究
  2014年
• 化学システム工学実験Ⅲ
  2014年
• 分子情報工学特論I
  2013年
• 化学工学基礎演習Ⅰ
  2013年
• 化学システム工学実験Ⅲ
  2013年
• システム工学概論
  2013年
• 化学プロセス数学
  2013年
• 化学システム工学演習
  2013年
• 化学システム工学実験Ⅲ
  2013年
• システム工学概論
  2013年
• 化学工学基礎演習Ⅰ
  2013年
• 分子情報工学特論Ⅰ
  2013年
• 化学プロセス数学
  2013年
• 化学システム工学演習
  2013年
• 応用化学特別実験
  2013年
• 化学工学基礎演習Ⅰ
  2012年
• 化学システム工学演習
  2012年
• 論文・文献講読
  2012年
• システム工学概論
  2012年
• 特別計画研究
  2012年
• 化学プロセス数学
  2012年

科学研究費助成事業

• 基盤研究(A)
  粘弾性マイクロジェットの能動制御と次世代製造プロセスへの展開
  自 2021年, 至 2021年
• 基盤研究(A)
  粘弾性マイクロジェットの能動制御と次世代製造プロセスへの展開
  自 2020年, 至 2020年
• 基盤研究(C)
  部分混和系におけるKorteweg効果を伴う界面流体力学の数値解析
  自 2019年, 至 2021年
• 基盤研究(A)
  高機能性マイクロジェットの生成法確立と医工学利用基盤の構築
  自 2019年, 至 2019年
• 基盤研究(A)
  高機能性マイクロジェットの生成法確立と医工学利用基盤の構築
  自 2018年, 至 2018年
• 基盤研究(A)
  高機能性マイクロジェットの生成法確立と医工学利用基盤の構築
  自 2017年, 至 2017年
• 基盤研究(C)
  反応界面レオロジーを基軸とする液相反応流研究の展開
  自 2016年, 至 2018年
• 挑戦的萌芽研究
  液液反応界面に生成されるゲルの粘弾性測定手法の確立とゲル生成を伴う反応流の研究
  自 2013年, 至 2015年

論文

• Three-dimensional visualization of the alkaline flooding process with in-situ emulsification for oil recovery in porous media
  She, Yun; Mahardika, Mohammad Azis; Hu, Yingxue; Patmonoaji, Anindityo; Matsushita, Shintaro; Suekane, Tetsuya; Nagatsu, Yuichiro
  JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
  ELSEVIER
  Alkaline flooding is a promising application for enhanced oil recovery through the in-situ formation of oil-inwater emulsions. However, the emulsification behavior for the improved oil sweeping efficiency varying from the total acid number (TAN) of crude oil is still vague, especially in porous media filled with high acidic oil. This study initially performs three-dimensional (3D) oil displacement experiments to investigate the effects of the TAN and the injected flow rate on the oil recovery performance using X-ray computed tomography. Consequently, the oil recoveries are confirmed to increase with the increasing acid concentration from multi-angle of the oil displacement patterns, fractal dimension, slice average concentration of the alkaline solution, and oil recovery curves. The optimum injected flow rate is confirmed to be 360 ml/h based on different series of flow rate experiments. Meanwhile, the fingering structure evolution is observed with respect to the immiscible fluid?fluid displacement. Nonlinear finger?finger interactions, such as tip-splitting, shielding, and coalescence, are also confirmed in the 3D porous media. Subsequently, two-dimensional pore-scale micromodel experiments are performed to verify the oil displacement mechanism that may occur in 3D porous media. With an increase in the acid concentration, the emulsification ability becomes stronger in the form of an emulsified transition from partial to full emulsification during the alkaline flooding process as a result of formed average emulsion droplet size ranging 156.1?78.8 ?m. Partial emulsification is predominated by the snap-off, splitting, and division processes, leading to many oil ganglia and/or oil droplets formation that are bigger than pores (128 ?m) and throats (39 ?m). Full emulsification is characterized by the proper size of oil droplet formation by the shearing action mechanism. Far smaller oil droplets are effectively entrained in the aqueous phase and passed through the pores and throats as a continuous phase, resulting in the most favorable oil displacement. The study results suggest that high oil recovery could only be achieved under the condition of the proper sizes of emulsion droplets matched with the pore?throat structure. Finally, we propose herein that in engineering application, alkaline flooding has the highest potential of improving oil recovery in high-acidity oil reservoirs because of full emulsification.
  2021年07月, 研究論文（学術雑誌）, 共同, 202, 0920-4105, DOI(公開)(r-map)
• Viscous fingering of miscible annular ring
  Sharma, Vandita; Othman, Hamirul Bin; Nagatsu, Yuichiro; Mishra, Manoranjan
  JOURNAL OF FLUID MECHANICS
  CAMBRIDGE UNIV PRESS
  Miscible viscous fingering (VF) of the annulus of a more viscous fluid radially displaced by a less viscous fluid is investigated through both numerical computations and experimental study. We aim to understand how VF with finiteness in a radial displacement different from the classical radial VF and the instability of a slice displaced rectilinearly with a uniform velocity. It is observed that the VF of a miscible annular ring is a persistent phenomenon in contrast to the transient nature of VF of a miscible slice. Although new fingers cease to appear after some time but due to the radial spreading of the area available for VF, a finite number of fingers always remain at a later time when diffusion is the ultimate dominating force. A statistical analysis is performed for the numerical data and it is found that the second moment of the averaged profile, variance, is a non-monotonic function of time, contrary to variance in classical radial VF and rectilinear VF with one fluid sandwiched between layers of another. The minimum in the variance indicates the interaction of two fronts which is visible in terms of pressure fingers, but not the concentration fingers indicating a faster growth of pressure than the concentration growth. In addition, for existence of critical parameters for instability in terms of viscosity contrast and amount of sample, the variation of the finger length with flow rate is found to be dependent on the amount of the more viscous fluid confined in the annulus.
  2021年04月06日, 研究論文（学術雑誌）, 共同, 916, 0022-1120, DOI(公開)(r-map)
• Enhanced Heavy Oil Recovery by Calcium Hydroxide Flooding with the Production of Viscoelastic Materials: Study with 3-D X-Ray Tomography and 2-D Glass Micromodels
  Mahardika, Mohammad Azis; She, Yun; Shori, Fujiura; Patmonoaji, Anindityo; Matsushita, Shintaro; Suekane, Tetsuya; Nagatsu, Yuichiro
  ENERGY & FUELS
  AMER CHEMICAL SOC
  In this study, the performance of calcium hydroxide (Ca(OH)(2)) flooding (CHF) was investigated with three-dimensional (3-D) experiments with microcomputed tomography and two-dimensional (2-D) micromodel experiments. In 3-D experiments for CHF, two stages of displacement occurred at high capillary numbers. First, streak-like patterns of viscous fingering developed up to the exit of the packed bed. After that, a stable displacement front propagated in the flow direction and resulted in an oil recovery of >50% of the initial oil in place. During the propagation of the stable displacement front, a high-pressure drop was established along the porous media. If CHF is followed by water flooding (WF), the stable front did not propagate and oil production declined promptly. CHF oil recovery is higher by approximately 30% than that of WF for all permeability ratios of heterogeneous layered porous media. We successfully demonstrated that CHF could improve significantly in homogeneous porous media and heterogeneous layered media. 2-D micromodel experiments suggest that a ganglion of Ca(OH)(2) blobs and folded membranes pushed out heavy oil at pore scale in a stable displacement front.
  2021年07月15日, 研究論文（学術雑誌）, 共同, 35, 14, 0887-0624, DOI(公開)(r-map), 11210, 11222
• Tunable Hydrodynamic Interfacial Instability by Controlling a Thermodynamic Parameter of Liquid-Liquid Phase Separation
  Suzuki, Ryuta X.; Kobayashi, Shuntaro; Nagatsu, Yuichiro; Ban, Takahiko
  JOURNAL OF PHYSICAL CHEMISTRY B
  AMER CHEMICAL SOC
  Herein, we report on the hydrodynamic interfacial instability controlled by a thermodynamic parameter driving the liquid-liquid phase separation during fluid displacement in a Hele-Shaw cell. This instability remains even when the solution is guaranteed to be hydrodynamically stable. Adjusting the salt concentration helps control the miscibility of the solutions and change the pattern of the interface. We observe stable circular, fingering, and droplet formation patterns as the salt concentration is decreased from equilibrium. In addition, we analyze this interfacial instability using thermodynamic flux, which is determined from the growth rate of the interface, and provide a theoretical framework to quantitatively predict the transition points between the patterns. We find that the patterns transition to a state having higher entropy production.
  2021年07月15日, 研究論文（学術雑誌）, 共同, 125, 27, 1520-6106, DOI(公開)(r-map), 7508, 7514
• Anomalous patterns of Saffman-Taylor fingering instability during a metastable phase separation
  Suzuki, Ryuta X.; Tada, Hikari; Hirano, Sae; Ban, Takahiko; Mishra, Manoranjan; Takeda, Risa; Nagatsu, Yuichiro
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS
  ROYAL SOC CHEMISTRY
  Phase separation is important in biology, biochemistry, industry, and other areas and is divided into two types: a spinodal decomposition type and a nucleation and growth type. The spinodal decomposition type phase separation occurs under the thermodynamically unstable conditions, and the nucleation and growth type phase separation occurs under thermodynamically metastable conditions. On the other hand, when a less viscous fluid displaces a more viscous one in porous media, the interface of the two fluids becomes hydrodynamically unstable and forms a finger-like pattern. The coupling of the hydrodynamic instability with the thermodynamic instability has been studied. It is reported that the hydrodynamic instability under thermodynamically unstable conditions, where spinodal decomposition type phase separation occurs, creates multiple moving droplets with a radius of 3-4 mm because of the spontaneous convection induced by the Korteweg force, which is driven by a compositional gradient during phase separation. However, the hydrodynamic instability under metastable conditions, where the phase separation of nucleation and growth type occurs, is still unrevealed. In this study, we applied fingering instability (hydrodynamic instability) under the metastable conditions, where the patterns are changed from fingering or droplets to anomalous patterns such as tip-widening or needle-like (top-pointed) fingering patterns when the initial concentration is metastable, which is considered near a binodal curve. These patterns are ubiquitous in nature, similar to dendrite crystals (snowflakes) or our body's cells. Thus, the patterns created can be controlled through hydrodynamic conditions such as the injection flow and thermodynamic conditions such as spinodal decomposition (thermodynamically unstable conditions) and metastable conditions.
  2021年05月14日, 研究論文（学術雑誌）, 共同, 23, 18, 1463-9076, DOI(公開)(r-map), 10926, 10935
• Effect of gas generation by chemical reaction on viscous fingering in a Hele-Shaw cell
  Wang, Weicen; Zhang, Chunwei; Patmonoaji, Anindityo; Hu, Yingxue; Matsushita, Shintaro; Suekane, Tetsuya; Nagatsu, Yuichiro
  PHYSICS OF FLUIDS
  AIP Publishing
  Herein, the effect of gas-bubble generation by a chemical reaction on viscous fingering (VF) is investigated using a Hele-Shaw cell in a miscible two-phase liquid. Sodium bicarbonate (NaHCO3) and citric acid (C6H8O7) solutions were used as displacing and displaced fluids, respectively. As factors affecting the displacement pattern with gas bubbles, four characteristic times of displacement, chemical reaction, bubble nucleation, and bubble coalescence, as well as the viscosity ratio, were discussed. In the experiments conducted herein, the characteristic time of the chemical reaction was shorter than those of other characteristic factors. Bubble coalescence occurred quickly, and the coalescence time was almost the same as the nucleation time. Therefore, if the displacement time changes with the injection flow rate, then the flow pattern changes depending on the competition between the displacement and nucleation times. When the displacement time was shorter than the nucleation time, the bubble generation did not follow the onset of VF. First, a VF pattern was formed, and small gas bubbles were then generated in the mixture inside the fingers. On the backbone of the fingers, small gas bubbles lined up and grew bigger with time. Moreover, when the nucleation time was lower than the displacement time, the bubbles coalesced more rapidly, thereby inducing outward flow with gas nucleation in addition to fluid injection. These gas bubbles prevented the mixing of the displacing and displaced fluids. Furthermore, the effects of C6H8O7 concentration and the viscosity ratio were discussed from the viewpoint of the characteristic time.
  2021年09月, 研究論文（学術雑誌）, 共同, 33, 9, 1070-6631, DOI(公開)(r-map)
• Growing Interface with Phase Separation and Spontaneous Convection during Hydrodynamically Stable Displacement
  Ban, Takahiko; Tanaka, Ryohei; Suzuki, Ryuta X.; Nagatsu, Yuichiro
  MATERIALS
  MDPI
  The displacement of one fluid by another is an important process, not only in industrial and environmental fields, such as chromatography, enhanced oil recovery, and CO2 sequestration, but also material processing, such as Lost Foam Casting. Even during hydrodynamically stable fluid displacement where a more viscous fluid displaces a less viscous fluid in porous media or in Hele-Shaw cells, the growing interface fluctuates slightly. This fluctuation is attributed to thermodynamic conditions, which can be categorized as the following systems: fully miscible, partially miscible, and immiscible. The dynamics of these three systems differ significantly. Here, we analyze interfacial fluctuations under the three systems using Family-Vicsek scaling and calculate the scaling indexes. We discovered that the roughness exponent, alpha, and growth exponent, beta, of the partially miscible case are larger than those of the immiscible and fully miscible cases due to the effects of the Korteweg convection as induced during phase separation. Moreover, it is confirmed that fluctuations in all systems with steady values of alpha and beta are represented as a single curve, which implies that accurate predictions for the growing interface with fluctuations in Hele-Shaw flows can be accomplished at any scale and time, regardless of the miscibility conditions.

  
  2021年10月, 研究論文（学術雑誌）, 共同, 14, 20, DOI(公開)(r-map)
• Enhancement of sonochemical reaction with the addition of aluminum powder in a sonoreactor
  Jingsong Zhou, Yutaka Tada, Yoshihito Kato, Yuichiro Nagatsu, Kyoichi Iwata, Katsufumi Yasui, Yuya Sakaguchi, Ryo Takebayashi
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  Enhancement of sonochemical reaction with the addition of aluminum powder in a sonoreactor is studied. The decolorization reaction between iodine and disodium hydrogenphosphate in a starch solution in the presence of aluminum powder proceeds at a maximum of 2 times faster than that in the absence of aluminum powder. The fast liquid flow is observed due to the reflection at the surface of the aluminum powder, which is in the shape of flakes in the water. The effect of the amount of aluminum powder on the chemical reaction is investigated.
  2010年04月20日, 研究論文（学術雑誌）, 共同, 43, 4, DOI(公開)(r-map), 389, 393
• Miscible viscous fingering involving viscosity changes of the displacing fluid by chemical reactions
  Yuichiro Nagatsu, Chika Iguchi, Kenji Matsuda, Yoshihito Kato, and Yutaka Tada
  Physics of Fluids
  AIP
  In our previous study, we experimentally studied the effects of changes in the viscosity of the displaced more-viscous liquid by instantaneous reactions on miscible viscous fingering pattern [Y. Nagatsu, K. Matsuda, Y. Kato, and Y. Tada, “Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions,” J. Fluid Mech. 571, 475 (2007)]. In the present study, experiments have been performed on the miscible viscous fingering involving changes in the viscosity of the displacing less-viscous liquid by instantaneous reactions in a radial Hele-Shaw cell. We have found that the shielding effect is suppressed and the fingers are widened when the viscosity is increased. As a result, the reaction makes the fingering pattern denser. In contrast, the shielding effect is enhanced, and the fingers are narrowed when the viscosity is decreased. As a result, the reaction makes the fingering pattern less dense. These results are essentially same as those obtained by the above-mentioned previous study. This shows that the effects of changes in the viscosity due to the instantaneous reactions are independent of whether the changes occur in the displaced liquid or in the displacing liquid. A mechanism for the independence is discussed.
  2010年02月, 研究論文（学術雑誌）, 共同, 22, 2, DOI(公開)(r-map), 024101
• 皿底円筒槽と平底円筒槽における撹拌所要動力の差異
  加藤禎人， 多田豊， 浦野邦彦， 中岡梓， 長津雄一郎
  化学工学論文集
  公益社団法人 化学工学会
  これまで撹拌槽に関する研究は非常に多くなされてきたが，大学側の研究対象は装置作成が容易である平底円筒槽に関するものがほとんどであり，実機に採用されている皿底円筒槽に関するデータは少なく，スケールアップにおいて，しばしば問題点とされてきた．本報では，皿底槽と平底槽との撹拌所要動力の差異がどのような撹拌槽で大きく現れるかを検討した．その結果，最も差が顕著に表れる撹拌槽の条件は，標準邪魔板条件の乱流状態で，放射流翼（主にパドル翼）を用いた場合であった．その際，皿底槽の撹拌所要動力は平底槽のそれに比べて最大約20%低下した．また，ピッチドパドル翼やプロペラ翼等の軸流が強い翼を使用した場合は，皿底槽と平底槽の間に動力の差異はなかった．さらに，邪魔板無し撹拌槽の場合は，旋回流支配になるためいずれの翼を使用しても，槽形状による動力の差異はなかった．
  2010年01月20日, 研究論文（学術雑誌）, 共同, 36, 1, DOI(公開)(r-map), 25, 29
• 乱流撹拌槽における羽根板面積が同じパドル翼の所要動力の差異
  加藤禎人， 多田豊， 浦野邦彦， 服部正寛， 長津雄一郎， 高承台， 李泳世
  化学工学論文集
  公益社団法人 化学工学会
  これまで撹拌所要動力に関する研究は非常に多くなされてきており，邪魔板無し撹拌槽に関しては永田の式をはじめとして種々の相関式が提案されている．しかし，邪魔板付き乱流撹拌槽に関しては翼の取り付け位置や槽の幾何形状によって所要動力が変動し，しばしば実機と実験装置との差異が問題になってきた．本研究では，永田の式の考え方では従来同じ動力を示すとされてきた幾何形状の撹拌翼に対し槽底形状，羽根枚数，羽根配置を変えた動力数を測定し，邪魔板付き乱流撹拌槽に関しては，それが大きく異なることを示した．ただし，邪魔板無し撹拌槽に関しては従来の永田の式の考え方が翼取り付け位置によらず成立していた．
  2010年01月20日, 研究論文（学術雑誌）, 共同, 36, 1, DOI(公開)(r-map), 30, 33
• Prediction of Mixing Pattern by Using Power Number Diagram in Baffled and Unbaffled Mixing Vessels
  Yoshihito Kato, Yutaka Tada, Yasuhiro Takeda, Naoka Atsumi, Yuichiro Nagatsu
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  Mixing patterns generated in stirred vessels for a wide range of Reynolds numbers were observed using a decolorization method based on the reaction between sodium thiosulfate and iodine. A relationship was established between the power number diagram (NP–Re diagram) and the shape of the isolated zone was observed. At low Reynolds numbers (laminar regime), the isolated zone resembled a doughnut ring, while a cylindrically rotating zone isolated at high Reynolds numbers (turbulent regime). Even with a small change in Reynolds number, the doughnut-ring-shaped isolated zone suddenly changed to a cylindrically rotating zone in an unbaffled vessel. The cylindrically rotating zone was not observed in baffled vessels at high Reynolds numbers. The clearance between the propeller impeller and the vessel bottom brought about a change in the mixing patterns, although the power consumption the remained constant.
  2010年01月20日, 研究論文（学術雑誌）, 43, 1, DOI(公開)(r-map), 46, 51
• Flow visualization and numerical analysis of a new mixing equipment with vibratory fins
  Yoshihito Kato, Setsuro Hiraoka, Shogo Fukumoto, Yutaka Tada, Yuichiro Nagatsu, Ryushin Ohmasa, Sung Tae Koh, Young Sei Lee
  Korean journal of chemical engineering
  Springer US
  The mixing performance of a new type of mixing equipment which has several fin oscillators on a pair of shafts with a vibrating motor was investigated. This mixing equipment, which is mainly used for industrial plating processes, was usually operated at a vibrating frequency of about 40 Hz with the amplitude 1 mm. The flow visualization in this equipment showed that the flow in the vessel at laminar flow region was vertically divided into two distinct symmetric regions. The numerical simulation of the flow and the mixing patterns agreed well with the visualization result at laminar flow region.
  2010年01月01日, 研究論文（学術雑誌）, 27, 1, DOI(公開)(r-map), 1, 5
• Hydrodynamics and Power Consumption of Rotating Baffled Shaking Cylindrical Vessel
  Yoshihito Kato, Yutaka Tada, Mami Inoue, Yuichiro Nagatsu, Young-Sei Lee, Song-Tae Koh
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  The hydrodynamics of a rotating baffled shaking cylindrical vessel was studied. When shaking frequency exceeded a critical value, the baffled shaking cylindrical vessel was operated in the out of phase mode and the wave height of liquid free surface in the vessel suddenly decreased. The mixing performance of the baffled vessel was lower than that of the nonbaffled vessel because of the sudden transition of the flow pattern in the baffled vessel from a rotational-wave type to a progressive-wave type at low shaking frequency. The shaking frequency can be correlated with the Froude number and the baffle conditions only, and it did not depend on the Reynolds number.
  2009年11月20日, 研究論文（学術雑誌）, 共同, 42, 11, DOI(公開)(r-map), 857, 860
• Effects of Sparger Geometry on Power Consumption and Mass Transfer in a Gas–Liquid Agitated Vessel with Disk Turbine
  Noboru Kamei, Yoshihito Kato, Yutaka Tada, Junichi Ando, Yuichiro Nagatsu
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  The power consumption, gas dispersion, and mass transfer volumetric coefficients are investigated in a gas–liquid agitated vessel with a disk turbine for various geometries, positions of the sparger, and directions of gas discharge. A sparger larger than the impeller is effective for obtaining high aeration power consumption and a high mass transfer volumetric coefficient. When the sparger is used, the flooding phenomenon does not occur easily. The gas is sufficiently dispersed when the large sparger is used, even if the gas is not blown directly into the impeller.
  2009年09月20日, 研究論文（学術雑誌）, 共同, 42, 9, DOI(公開)(r-map), 664, 668
• Effects of reflection plate on ultrasonic reaction in a sonoreactor
  Jingsong Zhou, Yutaka Tada, Yoshihito Kato, Yuichiro Nagatsu, Katsufumi Yasui, Yuya Sakaguchi, Ryo Takebayashi, Kyoichi Iwata
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  In order to improve the sonochemical efficiency of a sonoreactor, a metallic reflection plate is set in liquid. With the placement position and the diameter of the reflection plate varied at the same liquid height, a decolorization experiment using iodine and disodium hydrogenphosphate in starch solution has been carried out in order to examine the effects of the reflection plate on ultrasonic reaction. With the placement position of the reflection plate close to the liquid surface, the range of reaction field becomes much larger and the reaction proceeds more quickly. The diameter of the reflection plate has an optimum value for the sonochemical efficiency of the sonoreactor.
  2009年08月20日, 研究論文（学術雑誌）, 共同, 42, 8, DOI(公開)(r-map), 570, 575
• An experimental study of non-isothermal miscible displacements in a Hele-Shaw cell
  Yuichiro Nagatsu, Norihito Fujita, Yoshihito Kato, and Yutaka Tada
  Experimental Thermal and Fluid Science
  Elsevier
  Non-isothermal miscible displacements in a radial Hele-Shaw cell were experimentally investigated using a scheme in which room temperature liquids of relatively high viscosity were displaced by high-temperature (80 °C), less-viscous liquids. Fundamental characteristics have been presented regarding how the effect of a non-isothermal field on miscible displacement patterns varies in terms of factors such as the viscosity ratio of the more- and less-viscous liquids at 20 °C, M20, the rate of an increase in the pattern’s area, R, and the gap width of the cell, b. The concept of area density was used to quantitatively evaluate the effect of the non-isothermal fields on the patterns. We have found that the effect of the non-isothermal field on the patterns does not monotonically vary with M20 and b. In contrast, it increases with R in the present experimental condition. The experimental results can be explained by introducing an assumption in which heat is transferred mainly to the plates of the cell, in other words, the temperature of the more-viscous liquid remains constant, whereas that of the less-viscous liquid spatiotemporally decreases and the viscosity of it increases along with the temperature decrease. Visualization of non-isothermal field in the cell has been done by means of a thermo sheet and the results support the assumption mentioned above.
  2009年04月, 研究論文（学術雑誌）, 共同, 33, 4, DOI(公開)(r-map), 695, 705
• Effects of moderate Damköhler number on miscible viscous fingering involving viscosity decrease due to a chemical reaction
  Yuichiro Nagatsu, Yusuke Kondo, Yoshihito Kato, and Yutaka Tada
  Journal of Fluid Mechanics
  Cambridge University Press
  We have succeeded in experimentally investigating the effects of a moderate Damköhler number, Da (defined as the ratio between a characteristic time of fluid motion and that of a chemical reaction), for various Péclet numbers, Pe, on miscible viscous fingering involving a decrease in the viscosity of the displaced liquid due to a chemical reaction in Hele-Shaw cells. We achieved this by using a chemical reaction between a polymer solution and metal ions. Main analysis has been done for the radial fingering. In the range of Pe employed here, the fingering patterns without the reaction (Da = 0) were independent of Pe. The fingering patterns with the reaction depended on the single parameter, Da, and the area occupied by the fingering pattern near the injection hole increased with Da in the range of Da employed here. The ratio of the area occupied by the fingering pattern within the circle radius of which is the length of longest finger to the area of the circle increased with Da in the range of Da employed here. This result is opposite to that of Nagatsu et al. (J. Fluid Mech., vol. 571, 2007, p. 475), in which the area was decreased by the reaction decreasing the viscosity involving significantly high Da. Experiments in the linear geometry show that the shape of a single finger also depended on the single parameter, Da, and the finger width increased near the base with Da. This result is also opposite to that in the previous case in which the width of a single finger was considered to be decreased by the reaction. These results, interestingly, show that the effects of the decrease in the displaced liquid's viscosity due to chemical reaction on the fingering pattern for moderate Da are opposite to those for significantly high Da. A mechanism for the opposite effects on the fingering pattern depending on Da is discussed.
  2009年04月, 研究論文（学術雑誌）, 共同, 625, DOI(公開)(r-map), 97, 124
• Investigation of reacting flow fields in miscible viscous fingering by a novel experimental method
  Yuichiro Nagatsu, Takashi Ogawa, Yoshihito Kato, and Yutaka Tada
  AIChE Journal
  Wiley Subscription Services, Inc., A Wiley Company
  The reacting flow fields in reactive miscible viscous fingering in a Hele‐Shaw cell studied by Nagatsu and Ueda had not been completely elucidated, mainly because one cannot exactly recognize where and when the reaction takes place in the reactive fingering pattern. We developed a novel experimental method that allowed us to identify the reaction region in the fingering pattern employed in the previous studies. The novel method involves switching of the less‐viscous liquid injected in both the nonreactive and reactive experiments. By using the novel method, we succeeded in showing how the reaction region in the fingering pattern was affected by the initial reactant concentrations, the Péclet number, and time. We propose physical models of the reacting flow field in the cell's gap direction that can explain the obtained experimental results.
  2009年03月, 研究論文（学術雑誌）, 共同, 55, 3, DOI(公開)(r-map), 563, 580
• 乱流撹拌槽における非定常撹拌の効果
  加藤禎人， 多田豊， 武田康弘， 長津雄一郎， 岩田修一， 岩石真一， 梶原進， 李泳世， 高承台
  化学工学論文集
  公益社団法人 化学工学会
  ロボットなどに多く用いられているサーボモーターを乱流撹拌操作に応用した．モーターの断続的な運転，回転方向を反転させるなどの非定常な操作を撹拌操作に応用し，低粘度領域で邪魔板を使用しなくても効果的に混合できることがわかった．翼の断続的な運転操作は液混合に有効であり，回転方向を変動させるとより効果的だった．切換頻度は，正逆運転においては小さくした方が効果的だったが，運転切り替え時間を2秒以下にすると混合性能は低下した．トルクは，断続運転よりも正逆運転の方がより高い値を示した．単位体積当たりの動力で混合時間を評価した結果，非定常撹拌はかなり効果的であることが分かった．
  2009年01月20日, 研究論文（学術雑誌）, 共同, 35, 1, DOI(公開)(r-map), 152, 157
• Correlation of power consumption for propeller and pfaudler type impellers
  Yoshihito Kato, Yutaka Tada, Yasuhiro Takeda, Yasuhiro Hirai, Yuichiro Nagatsu
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  Power consumption in unbaffled and baffled agitated vessels with propeller and pfaudler type impellers is measured over a wide range of Reynolds numbers from laminar to turbulent flow regions. The power correlation for the propeller and pfaudler type impellers is derived from modification of the previously proposed power correlation for a paddle impeller. The calculated correlation values agree well with experimental ones, and the same correlation can be applied to both propeller and pfaudler type impellers.
  2009年01月20日, 研究論文（学術雑誌）, 共同, 42, 1, DOI(公開)(r-map), 6, 9
• ボルテックスリングの液体混合に及ぼす効果
  加藤禎人， 多田豊， 原田拡， 長津雄一郎， 中谷哲治
  化学工学論文集
  公益社団法人 化学工学会
  ボルテックスリングが液体混合に及ぼす効果を検討した．円形のパイプからボルテックスリングを発生させ，容器内の流速を測定した結果，ボルテックスリングの流速はほとんど減衰しなかった．また，同じ平均流量でリングが発生する系とリングが発生しないジェット撹拌とを比較した結果，リングを発生する系のほうが混合時間が短くなった．これにより，ボルテックスリングが混合促進効果を持つことが実験的に明らかとなった．
  2008年11月20日, 研究論文（学術雑誌）, 34, 6, DOI(公開)(r-map), 562, 565
• Effect of Ultrasonic Irradiation on Chemical Reaction in Iodine Solution Decolorization Experiment
  Jingsong Zhou, Yutaka Tada, Yoshihito Kato, Yuichiro Nagatsu, Katsufumi Yasui
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  In order to investigate the region of effective chemical reaction field in a sonoreactor, the power input per unit volume of liquid and the liquid height were varied. Decolorization experiments using iodine and disodium hydrogenphosphate in a starch solution under chemical reaction rate control conditions were carried out and the effect of ultrasonic irradiation on the chemical reaction was examined. The region of the effective chemical reaction field depended on the power input per unit volume dissipated in the liquid but did not depend on the liquid height. With increasing the power input per unit volume of the liquid, the region of the effective chemical reaction field became larger and the effective chemical reaction rate increased.
  2008年11月20日, 研究論文（学術雑誌）, 共同, 41, 11, DOI(公開)(r-map), 1055, 1060
• Spiral pattern in a radial displacement involving a reaction producing gel
  Yuichiro Nagatsu, Atsushi Hayashi, Mitsumasa. Ban, Yoshihito Kato, and Yutaka Tada
  Physical Review E
  American Physical Society
  We have shown experimentally that the pattern created by the displacement of a more viscous fluid by a less viscous one in a radial Hele-Shaw cell develops not radially but spirally when a more viscous sodium polyacrylate solution is displaced by a less viscous trivalent iron ion (Fe3+) solution with a sufficiently high concentration of Fe3+. Another experiment revealed that an instantaneous chemical reaction takes place between the two fluids, and at high Fe3+ concentrations it produces a film of the gel at the contact plane. The gel film is proposed to be responsible for the spiral pattern.
  2008年08月26日, 研究論文（学術雑誌）, 共同, 78, 2, DOI(公開)(r-map), 026307
• Miscible viscous fingering with a chemical reaction involving precipitation
  Yuichiro Nagatsu, Si-Kyun Bae, Yoshihito Kato, and Yutaka Tada
  Physical Review E
  American Physical Society
  We experimentally investigated the effects of a chemical reaction involving precipitation on the miscible viscous fingering pattern formed in a Hele-Shaw cell. The precipitation concentration, the ratio of the reactant concentrations initially included in the more- and less-viscous liquids, and the Péclet number were varied. For a Péclet number at the stoichiometric ratio the precipitation had significant effects on the fingering pattern when its concentration exceeded a threshold value. Interestingly, the type of effect of the precipitation on the pattern depended on its concentration. At moderate concentration, a straight-shaped finger was observed. At high concentration, the finger was bent in an almost perpendicular direction. The effect of precipitation on the pattern also depended on the ratio of reactant concentrations.
  2008年06月18日, 研究論文（学術雑誌）, 共同, 77, 6, DOI(公開)(r-map), 067302
• Miscible displacements with a chemical reaction in a capillary tube
  Yuichiro Nagatsu, Yuji Hosokawa, Toshihisa Ueda, Yoshihito Kato, and Yutaka Tada
  AIChE Journal
  Wiley Subscription Services, Inc., A Wiley Company
  Miscible displacement of a more‐viscous liquid by a less‐viscous one with a chemical reaction in a capillary tube was investigated experimentally and theoretically. In such a flow field, the less‐viscous liquid continuously leaks from the tip of the finger‐shaped boundary between the two liquids to form another thin finger depending on flow condition. This is called a “spike.” Experimental results show that in the spike product is clearly or scarcely observed when the initial reactant concentration in the less‐viscous liquid is sufficiently larger or smaller than the stoichiometry, respectively. On the basis of theoretical results, a model is proposed in which the difference in the reaction plane's location in either the less‐viscous liquid or in the boundary (determined by the variation in the initial reactant concentrations) results in a significant difference between the locations of the boundary and the reaction plane, this difference being affected by the spike configuration of the boundary.
  2008年03月, 研究論文（学術雑誌）, 共同, 54, 3, DOI(公開)(r-map), 601, 613
• 新型 2 軸撹拌翼オクタジットの流動特性
  加藤禎人， 多田豊， 佐藤裕子， 原田拡， 長津雄一郎， 中谷哲治
  化学工学論文集
  公益社団法人 化学工学会
  低動力で数Pa·sまでの液粘度の流体を撹拌可能な，非定常的な流れを発生させる新しい撹拌翼が野村マイクロ・サイエンス（株）によって開発された．この撹拌機は半円形の立体翼を互いに逆方向に回転する2軸で架橋した撹拌翼である．最大の特徴はボルテックスリングを連続的に発生させて液を流動させることで，比較的広い粘度範囲の液を撹拌できる．このオクタジットの性能を評価するために混合時間，循環時間分布，撹拌所要動力を測定し，乱流域では循環時間分布のピークが一つで，同等の撹拌所要動力ではディスクタービンより短い混合時間を得た．
  2007年, 研究論文（学術雑誌）, 共同, 33, 3, DOI(公開)(r-map), 195, 200
• 非定常撹拌に対する非対称翼の適用
  加藤禎人， 多田豊， 伴昌子， 長津雄一郎， 柳本和司
  化学工学論文集
  公益社団法人 化学工学会
  翼が一回転する間に撹拌速度が変化する混合性能を評価した．渦の中心が移動するために，層流撹拌で発生するドーナツ状の未混合領域は消失し，混合時間は飛躍的に減少した．低粘度撹拌に用いられる通常の翼を層流撹拌に用いた場合，非定常な撹拌操作は非常に有効であるが，非対称翼を用いることにより，さらに有用であることが確認できた．
  2007年, 研究論文（学術雑誌）, 33, 1, DOI(公開)(r-map), 16, 19
• Transport Phenomena around Cylindrical Baffle in an Agitated Vessel Measured using an Electrochemical Method
  Yoshihito Kato, Noboru Kamei, Yutaka Tada, Yushi Iwasaki, Yuichiro Nagatsu, Shuichi Iwata, Young-Sei Lee, Song-Tae Koh
  J Chem Eng Jpn
  The mass transfer coefficient of cylindrical baffles in an agitated vessel has been measured for the first time with the constant potential method using aqueous solution of 1 N-KOH + 0.2 N-K4Fe(CN)6 + 0.01 N-K3Fe(CN)6. The average mass transfer coefficient on the baffles was three to five times larger than that of the vessel wall based on the power consumption per unit volume. The average mass transfer coefficient on the baffles increased with decreasing baffle diameter. The number of baffles, the clearance between the baffles and vessel wall, the position of the baffles and the position of the impeller did not affect the average mass transfer coefficient of the baffles under these experimental conditions. The average mass transfer coefficient of the cylindrical baffles measured herein agrees with the value obtained by an equation based on one published before. The distributions of the local mass transfer coefficient of the cylindrical baffles are shown graphically for various impeller speeds. The local mass transfer coefficient of the baffles near the impeller was larger than those in other positions, and that near the liquid free surface increased up to the same level as that of the baffles near the impeller as the impeller speed increased.
  2007年, 研究論文（学術雑誌）, 40, 8, DOI(公開)(r-map), 611, 616
• Generalized Peng–Robinson equation of state with pair potential parameters for liquid n-alkanes
  Yutaka Tada, Akihiko Tamakoshi, Yoshihito Kato, Yuichiro Nagatsu
  Fluid phase equilibria
  Elsevier
  Peng–Robinson EOS is generalized with pair potential parameters for the PVT relation of liquid n-alkanes C1 to C30, C32, and C36 with the saturated vapors for temperatures near the normal boiling point to the critical point. The EOS is reduced with the Lennard–Jones pair potential depth parameter ɛ and the characteristic length d, which is determined with the pair potential parameters ɛ and σ. Two reduced parameters in the EOS, aˆ=a/(NA2εd3)andbˆ=b/(NAd3) , where NA is Avogadro number, are in the corresponding states with reduced temperature, Tˆ=kT/ε . The pair potential parameters ɛ and σ are expressed by universal functions of temperature reduced with critical temperature, Tr = T/Tc. The values of the coefficients in the functions are specific to each alkane. The vapor pressure and the liquid molar volume calculated with the EOS agreed to the observed ones with the root mean square deviation of 2.21% and 0.63%, respectively, better than those from the modified PR-EOS in the literature. The coefficients and the powers in the universal functions for ɛ and σ are expressed by generalized functions of acentric factor ω, where the calculated vapor pressure and liquid molar volume agreed well to the observed ones with the root mean square deviation of 4.16% and 1.57%, respectively.
  2007年12月15日, 研究論文（学術雑誌）, 共同, 262, 1-2, DOI(公開)(r-map), 236, 243
• 互いに混ざり合い粘度の大きく異なる二液相反応流
  長津雄一郎， 植田利久
  日本燃焼学会誌= Journal of the Combustion Society of Japan
  日本燃焼学会
  2007年08月31日, （MISC）総説・解説（学術雑誌）, 共同, 49, 149, 174, 180
• Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions
  Yuichiro Nagatsu, Kenji Matsuda, Yoshihito Kato, and Yutaka Tada
  Journal of Fluid Mechanics
  Cambridge University Press
  When a reactive and miscible less-viscous liquid displaces a more-viscous liquid in a Hele-Shaw cell, reactive miscible viscous fingering takes place. We succeed in showing experimentally how a reactive miscible viscous fingering pattern in a radial Hele-Shaw cell changes when the viscosity of the more-viscous liquid is varied owing to variation in chemical species concentration induced by an instantaneous chemical reaction. This is done by making use of a polymer solution's dependence of viscosity on pH. When the viscosity is increased by the chemical reaction, the shielding effect is suppressed and the fingers are widened. As a result, the ratio of the area occupied by the fingering pattern in a circle whose radius is the length of the longest finger is larger in the reactive case than in the non-reactive case. When the viscosity is decreased by the chemical reaction, in contrast, the shielding effect is enhanced and the fingers are narrowed. These lead to the area ratio being smaller in the reactive case than in the non-reactive case. A physical model to explain this change in the fingering pattern caused by the chemical reaction is proposed.
  2007年01月, 研究論文（学術雑誌）, 共同, 571, DOI(公開)(r-map), 475, 493
• サーボモーターを用いた非定常撹拌の性能評価
  加藤禎人， 多田豊， 仲道真也， 長津雄一郎， 岩田修一， 岩石真一， 梶原進， 李泳世， 高承台
  化学工学論文集
  公益社団法人 化学工学会
  近年ロボットなどに多く用いられているサーボモーターを撹拌操作に応用した．モーターの断続的な運転，回転方向の反転，また，翼を上下移動させるなどの非定常な操作を撹拌操作に応用し，ディスクタービンという主に低粘度領域で使用される撹拌翼でも低レイノルズ数領域で効果的に使用できることがわかった．翼の断続的な運転操作は液混合に有効であり，切換頻度を大きくした方が効果的だった．また，翼の上下移動では移動速度と移動距離を大きくすることが効果的だった．さらに，翼の断続的な運転と上下移動を組合せれば，その相乗効果によりさらに混合性能が良くなった．また，低Re数では不等速撹拌よりも混合性能が良くなった．
  2006年, 共同, 32, 6, DOI(公開)(r-map), 465, 470
• オリジナルバッフルを備えた改良型アンカー翼 (NX Mixer) の性能評価
  加藤禎人， 多田豊， 長津雄一郎， 佐藤裕子， 岩崎雄志， 松田健次， 岩石真一， 平岡節郎
  化学工学論文集
  公益社団法人 化学工学会
  アンカー翼を改良し，広い粘度域での混合と槽壁での伝熱が良好なオリジナルバッフルを備えた新型撹拌翼（NX Mixer 1型，2型）が開発された．NX Mixerの混合性能を評価するため脱色法により混合時間を測定したところ，NX Mixer 2型で混合時間が短縮されることが確認された．また，NX Mixerの性能を評価するために固液物質移動係数を電気伝導度法により測定した．消費動力と固液物質移動係数の関係は他の大型翼の関係と同様であった．通気下ではNX Mixerの固液物質移動係数は他の大型翼より大きくなった．NX Mixerの気液物質移動係数をダイナミック法を用いて測定したところ，気液物質移動係数はラシュトンタービン翼より小さくなった．これはNX Mixerのガスホールドアップがラシュトンタービン翼より小さいからであると考えられる．気液物質移動係数はHiraoka et al.（2001）による式を修正することにより相関された．さらに，撹拌槽の槽壁近傍での平均物質移動係数および局所物質移動係数を希薄溶液系のイオン移動を利用して測定した結果，NX Mixerは槽壁と翼とのクリアランスが狭いアンカー翼を主翼とするために他の大型翼より槽壁の上部から下部にわたって高い局所物質移動係数が得られた．
  2005年, 研究論文（学術雑誌）, 共同, 31, 3, DOI(公開)(r-map), 159, 167
• 8 の字振とうによる揺動撹拌槽における混合条件と固液および気液物質移動
  加藤禎人， 多田豊， 渡辺祥子， 長津雄一郎， 岩田修一， 李泳世， 高承台
  化学工学論文集
  公益社団法人 化学工学会
  8の字揺動撹拌について実験的に流動状態を観察，固液および気液物質移動係数を測定した．槽内の流動状態は振動数の増加とともにある振動数を境にして数パターン（進行波型，旋回流反転型，旋回流安定型，進行波型）の変化を伴うが，液混合に適した操作範囲が往復揺動撹拌よりも若干広くなった．また，固液間物質移動係数は旋回揺動撹拌と全く同じ式で相関でき，気液間物質移動容量係数も定数項は異なるものの旋回揺動撹拌の式と同型の相関式で表された．
  2005年, 研究論文（学術雑誌）, 共同, 31, 6, DOI(公開)(r-map), 394, 398
• Improvement of mixing efficiencies of conventional impeller with unsteady speed in an impeller revolution
  Yoshihito Kato, Yutaka Tada, Masako Ban, Yuichiro Nagatsu, Shuichi Iwata, Kazushi Yanagimoto
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  An unsteady mixing speed was applied to laminar mixing in a vessel containing a conventional impeller. Three non-circle cams were combined to generate the unsteady speed in an impeller revolution. The mixing performances of the unsteady speed impeller were compared with those of a conventional impeller operated under a steady speed. The mixing time and the flow pattern were measured by flow visualization using the discoloration method in which sodium thiosulfate reacts with an iodine solution. Because the unsteady motion moved the center of the vortices, the doughnut rings above and below the impeller disappeared when unsteady mixing was employed.
  2005年, 研究論文（学術雑誌）, 38, 9, DOI(公開)(r-map), 688, 691
• Effects of Liquid Film Formed on Flask Surface on Oxygen Transfer Rate in Shaking Flask and Development of Baffled Shaking Vessel by Optical Method Based on Sulfite Oxidation
  Yoshihito Kato, Yutaka Tada, Eri Iwanaga, Yuichiro Nagatsu, Shuichi Iwata, Young-Sei Lee, Song-Tae Koh
  Journal of Chemical Engineering of Japan
  [Tokyo] Society of Chemical Engineers, Japan.
  The gas liquid mass transfer volumetric coefficients KLa in several kinds of small size shaking flasks were measured with an optical method based on sulfite oxidation without oxygen concentration probe and liquid sampling. It was found that the liquid film on the inner surface of a flask was one of the very important factors to increase KLa. The baffled flask was effective to obtain a larger oxygen transfer rate than the normal flask. A new developed baffled cylindrical vessel based on the baffled small flask has about three times larger KLa than the normal vessel.
  2005年, 研究論文（学術雑誌）, 38, 11, DOI(公開)(r-map), 873, 877
• Analytical study on effects of finger-growth velocity on reaction characteristics of reactive miscible viscous fingering by using a convection-diffusion-reaction model
  Yuichiro Nagatsu and Toshihisa Ueda
  Chemical Engineering Science
  Pergamon
  Reactive miscible viscous fingering occurs when a reactive and miscible less-viscous liquid displaces a more-viscous liquid. Effects of bulk finger-growth velocity on reaction characteristics of miscible viscous fingering with a chemical reaction were studied analytically by using a convection–diffusion–reaction model. The model assumes the existence of a distinct interface between both liquids, assumes the existence of a two-dimensional, steady, stagnated flow field in the less-viscous liquid, and assumes an infinite chemical reaction rate. The model was then used to determine the reaction characteristics, such as the location of the reaction surface and the profile of the product, as functions of the velocity and initial reactant concentrations. The results reveal that the effects of the velocity on the reaction characteristics can be divided into low-, intermediate-, and high-velocity regions. In the low-velocity region, the reaction characteristics strongly depend on the reactant concentrations. In the intermediate-velocity region, the dependence of the reaction characteristics on the reactant concentrations decreases with increasing velocity. In the high-velocity region, the reaction characteristics are nearly independent of the reactant concentrations. Experiments confirm the existence of these three velocity regions predicted by the model.
  2004年09月, 研究論文（学術雑誌）, 共同, 59, 18, DOI(公開)(r-map), 3817, 3826
• Effects of finger-growth velocity on reactive miscible viscous fingering
  Yuichiro Nagatsu and Toshihisa Ueda
  AIChE Journal
  Wiley Subscription Services, Inc., A Wiley Company
  2003年03月, 研究論文（学術雑誌）, 共同, 49, 3, DOI(公開)(r-map), 789, 792
• Effects of reactant concentrations on reactive miscible viscous fingering
  Yuichiro Nagatsu and Toshihisa Ueda,
  AIChE Journal
  Wiley Subscription Services, Inc., A Wiley Company
  Effects of reactant concentrations on the characteristics of reactive miscible viscous fingering in a Hele‐Shaw cell at low finger‐growth velocity were studied both experimentally and theoretically. The product distribution varies with the variations in the initial reactant concentrations and depends on the location of a reaction zone. When the reaction zone is located in the more‐viscous‐liquid region the product concentrates at the fingertips, but when it is located in the less‐viscous‐liquid region, the product spreads in a relatively broad area inside the fingers. This significant difference in the reaction pattern resulting from variations in the reactant concentrations is caused by the large difference of molecular diffusivity in the two liquids, that is, of viscosity which is one of the important factors for viscous fingering. These results are confirmed theoretically by one‐dimensional diffusive–reactive analysis.
  2001年08月, 研究論文（学術雑誌）, 共同, 47, 8, DOI(公開)(r-map), 1711, 1720
• Experimental study of miscible viscous fingering with different effective interfacial tension
  Suzuki, Ryuta X.; Quah, Fu Wei; Ban, Takahiko; Mishra, Manoranjan; Nagatsu, Yuichiro
  AIP ADVANCES
  AMER INST PHYSICS
  Viscous fingering (VF) occurs when a more viscous fluid is displaced by a less viscous one in porous media or in Hele-Shaw cells. Generally, VF can be divided into two types: immiscible VF and miscible VF. The typical immiscible finger is wider than the equivalent miscible finger because of interfacial tension. Recently, it has been pointed out that an effective interfacial tension (EIT) is present even in miscible systems when there is a steep concentration gradient of chemical species at the interface. The effects of EIT on miscible VF have so far mainly been studied numerically showing that the fingers become wider owing to EIT. Here, we perform an experimental investigation of the effects of EIT on miscible VF by establishing two solution systems that have different concentration differences but the same viscosity contrast. One is a glycerol solution with a concentration of 99 wt.% and water and has a higher water concentration difference of Cw = 99 wt.%. The other is a polymer solution with a concentration of 8.5 wt.% and water and has a lower water concentration difference of Cw = 8.5 wt.%. We show by direct measurement with a spinning drop tensiometer that the glycerol-water system exhibits greater EIT, and we demonstrate experimentally that typical fingers with high EIT become wider than those with low EIT. We suggest that under the experimental condition employed, the VF in the glycerol-water system with high EIT exhibits a characteristic property of immiscible VF, although it has generally been regarded as a typical representative of classical miscible VF.
  2020年11月01日, 研究論文（学術雑誌）, 共同, 10, 11, DOI(公開)(r-map)
• Fluid Morphologies Governed by the Competition of Viscous Dissipation and Phase Separation in a Radial Hele-Shaw Flow
  Suzuki, Ryuta X.; Takeda, Risa; Nagatsu, Yuichiro; Mishra, Manoranjan; Ban, Takahiko
  COATINGS
  MDPI
  The displacement of a less viscous fluid by a more viscous fluid in a radial Hele-Shaw cell makes a circular pattern because the interface is hydrodynamically stable in this condition. Very recently, it has been experimentally reported that the hydrodynamically stable displacement in a partially miscible system induces fingering patterns while stable circular patterns are made at fully miscible and immiscible systems. The fingering instability in the partially miscible system results from complex and entangled elements involving viscous dissipation, molecular diffusion, and phase separation. The analyzing mechanism requires a quantitative relationship between the hydrodynamic interfacial fingering patterns and underlying physicochemical properties. Here, we experimentally investigated the change in fluid patterns formed by the progression of phase separation in the partially miscible systems and categorized them into three patterns: finger-like pattern, annular-like pattern, and circular pattern. Moreover, we propose the mechanism of the pattern formation by an interfacial tension measurement and evaluate the patterns by modified capillary number and newly defined body force ratio, B-f. Our analysis revealed that the deformation index of the pattern can be expressed as a function of B-f on a single curve regardless of the miscibility.
  2020年10月, 研究論文（学術雑誌）, 共同, 10, 10, DOI(公開)(r-map)
• Chemical Flooding for Enhanced Heavy Oil Recovery via Chemical-Reaction-Producing Viscoelastic Material
  Nagatsu, Yuichiro; Abe, Kizuna; Konmoto, Kaori; Omori, Keiichiro
  ENERGY & FUELS
  AMER CHEMICAL SOC
  Chemical flooding has great potential for enhancing heavy oil recovery, especially for reservoirs in which thermal methods are not suitable. Recently, it has been recognized that lower recovery of heavy oil by water flooding is attributed to an inefficient sweep in the pore scale and not the residual oil in the swept region for conventional oil. This paper presents a novel chemical flooding for enhanced heavy oil recovery, focusing on this idea. In this method, an alkaline solution including an alkaline earth metal ion is injected into heavy oil that possesses acidic components. Here, Ca(OH)(2) solution was used as an alkaline solution including an alkaline earth metal ion. Further, a heavy oil model containing an acid component, i.e., a paraffin oil including a fatty acid, was used. Metallic soap is generated by chemical reaction precipitates at the oil-water interface, which behaves as a viscoelastic material. The viscoelastic material in the pore blocks the preferentially swept region and improves the sweep efficiency. To maximize its effect, we propose a method involving the injection of Ca(OH)(2) solution prior to water flooding as opposed to the conventional methods, wherein the chemicals are injected after water flooding. Also, we propose a continuous Ca(OH)(2) injection method, where the cumulative oil recovery reached around 55% initial oil in place (IOIP%), which was much larger than that of water flooding (33 IOIP%) and conventional alkaline flooding (35 IOIP%). In addition, we show that the novel flooding method proposed can be applied to heavy oil reservoirs after water flooding. Furthermore, the novel flooding enhanced heavy oil recovery in the wide range of the concentration of acid tested. Additionally, we find that the viscoelasticity is maintained up to 80 degrees C. The proposed method benefits from the adversity of the precipitate formed by a divalent ion (as a result of using polymer, surfactant, or alkali), which is commonly regarded as an undesirable factor for chemical flooding. This method is surfactant- and polymer-free. On the basis of these considerations, this study introduces a novel chemical flooding method for enhanced recovery of heavy oil, which is inexpensive, high-divalent-ion-tolerant, high-temperature-tolerant, and energy-saving.
  2020年09月17日, 研究論文（学術雑誌）, 共同, 34, 9, 0887-0624, DOI(公開)(r-map), 10655, 10665
• Phase separation effects on a partially miscible viscous fingering dynamics
  Suzuki, Ryuta X.; Nagatsu, Yuichiro; Mishra, Manoranjan; Ban, Takahiko
  JOURNAL OF FLUID MECHANICS
  CAMBRIDGE UNIV PRESS
  Classical viscous fingering (VF) instability, the formation of finger-like interfacial patterns, occurs when a less viscous fluid displaces a more viscous one in porous media in immiscible and fully miscible systems. However, the dynamics in partially miscible fluid pairs, exhibiting a phase separation due to its finite solubility into each other, has not been largely understood so far. This study has succeeded in experimentally changing the solution system from immiscible to fully miscible or partially miscible by varying the compositions of the components in an aqueous two-phase system (ATPS) while leaving the viscosities relatively unchanged at room temperature and atmospheric pressure. Here, we have experimentally discovered a new topological transition of VF instability by performing a Hele-Shaw cell experiment using the partially miscible system. The finger formation in the investigated partially miscible system changes to the generation of spontaneously moving multiple droplets. Through additional experimental investigations, we determine that such anomalous VF dynamics is driven by thermodynamic instability such as phase separation due to spinodal decomposition and Korteweg convection induced by compositional gradient during such phase separation. We perform the numerical simulation by coupling hydrodynamics with such chemical thermodynamics and the spontaneously moving droplet dynamics is obtained, which is in good agreement with the experimental investigations of the ATPS. This numerical result strongly supports our claim that the origin of such anomalous VF dynamics is thermodynamic instability.
  2020年09月10日, 研究論文（学術雑誌）, 共同, 898, 0022-1120, DOI(公開)(r-map)
• Numerical simulations of miscible viscous fingering involving viscosity changes of the displacing fluid by A + B -> C chemical reactions
  Omori, Keiichiro; Nagatsu, Yuichiro
  AIP ADVANCES
  AMER INST PHYSICS
  Nagatsu and De Wit [Viscous fingering of a miscible reactive A + B -> C interface for an infinitely fast chemical reaction: Nonlinear simulations, Phys. Fluids 23, 043103 (2011)] simulated the nonlinear evolution of reactive miscible viscous fingering (VF) where the viscosity of the more viscous displaced fluid was changed by an instantaneous A + B -> C chemical reaction. They analyzed the dynamics from the viewpoint of an underlying viscosity profile reconstructed from the concentrations of chemical species obtained by a one-dimensional diffusion-reaction equation. The present study develops a mathematical model for reactive miscible VF where the viscosity of the less viscous displacing fluid is changed by an instantaneous A + B -> C chemical reaction. We obtain the same underlying viscosity profile as Nagatsu and De Wit by employing appropriate parameters. We perform numerical simulations of the nonlinear evolution of VF under these appropriate parameters. The results show that the present numerical solutions are exactly the same as those obtained by Nagatsu and De Wit, i.e., the same VF pattern is obtained. This numerically proves that the effects of a viscosity change by the chemical reaction on VF are independent of whether the viscosity of the displaced or displacing fluid changes. We obtain a mathematical formula to describe the switch from the parameters used by Nagatsu and De Wit to those used in this study to obtain the same shape of the underlying viscosity profile. This finding will lead to easier and more flexible VF chemical control methods in geoscience processes, where it is difficult to manipulate the properties of more viscous fluids, by manipulating the properties of less viscous fluids.
  2020年09月01日, 研究論文（学術雑誌）, 共同, 10, 9, DOI(公開)(r-map)
• Fingering pattern induced by spinodal decomposition in hydrodynamically stable displacement in a partially miscible system
  Ryuta X. Suzuki, Yuichiro Nagatsu, Manoranjan Mishra, and Takahiko Ban
  Phys. Rev. Fluids
  2019年10月29日, 研究論文（学術雑誌）, 共同, 4, DOI(公開)(r-map), 104005
• Numerical study of immiscible viscous fingering in chemically reactive Hele-Shaw flows: Production of surfactants
  Tsuzuki, Reiko; Li, Qian; Nagatsu, Yuichiro; Chen, Ching-Yao
  PHYSICAL REVIEW FLUIDS
  AMER PHYSICAL SOC
  Viscous fingering on chemically reactive and immiscible interface is simulated by the phase-field method. The reaction produces surfactants on the interface to reduce local interfacial tension. Parametric analysis regarding the influences of reaction, determined by the dimensionless Damkohler number (Da) and the saturated capillary coefficient (epsilon(s)), on the fingering prominence at a prescribed breakthrough time is presented. The injection rate and viscosity ratio are also varied to observe their influences on the patterns. Transported by the fountain flows formed in the fingers, the produced surfactants tend to accumulate on the sides of fingers to weaken the local interfacial tension so that great variation of capillary effect will exist along the interface, especially for an intermediate range of Da. The weaker local capillary effect on a finger's side could result in prominent side-branching instability. Nonmonotonic behavior regarding the prominence of fingering instability for continuously increased injection flow rate observed in experiments is confirmed and explained qualitatively by the simulations. A reference capillary number (Ca-R) is proposed which is capable to monotonically describe the viscous fingering associated with both temporal and spatial changes of interfacial tension by reaction.
  2019年10月16日, 研究論文（学術雑誌）, 共同, 4, 10, 2469-990X, DOI(公開)(r-map)
• Unpredictable Dynamics of Polymeric Reacting Flow by Comparison between Pre- and Post-Reaction Fluid Properties: Hydrodynamics Involving Molecular Diagnosis via ATRFTIR Spectroscopy
  Toshimasa Ueki, Jun Iijima, Satoshi Tagawa, Yuichiro Nagatsu
  J. Phys. Chem. B
  2019年06月02日, 研究論文（学術雑誌）, 共同, 123, DOI(公開)(r-map), 4587, 4593
• Three-dimensional visualization of viscous fingering for non-Newtonian fluids with chemical reactions that change viscosity
  Sotheavuth Sin, Tetsuya Suekane, Yuichiro Nagatsu, Anindityo Patmonoaji
  Phys. Rev. Fluids
  2019年05月01日, 研究論文（学術雑誌）, 共同, 4, DOI(公開)(r-map), 054502
• Deviation from capillary number scaling of nonlinear viscous fingering formed by the injection of Newtonian surfactant solution
  Reiko Tsuzuki, Ryohei Tanaka, Takahiko Ban, and Yuichiro Nagatsu
  Phys. Fluids
  2019年04月01日, 研究論文（学術雑誌）, 共同, 31, DOI(公開)(r-map), 042108
• Dual role of surfactant-producing reaction in immiscible viscous fingering evolution
  Tsuzuki, Reiko; Ban, Takahiko; Fujimura, Masanari; Nagatsu, Yuichiro
  PHYSICS OF FLUIDS
  AMER INST PHYSICS
  An experimental study on immiscible viscous fingering (VF) with chemical reaction is described, whereby a surfactant produced in a radial Hele-Shaw cell results in a decrease in interfacial tension. The surfactant is formed at the interface between alkaline solution (sodium hydroxide) and a long-chain fatty acid (linoleic acid). This topic is closely related to alkaline flooding, which is an enhanced oil recovery method. The reaction was found to have two opposing effects on VF depending on the flow rate, namely, narrowing and widening of the fingers. Moreover, the influences of the reaction on VF evolution can be categorized into five different types based on the effects appearing in VF evolution and the fingering width and area at the maximum observation region. Possible mechanisms for each type are proposed, and an argument based on scaling of the VF properties using dimensionless numbers gives support to the proposed mechanisms. This dual role of the reaction in immiscible VF evolution may contribute to establishing optimal conditions for alkaline flooding. Moreover, the finding that one chemical reaction has two opposing effects on flow is of value from the standpoint of fundamental studies of reacting flow dynamics. Published under license by AIP Publishing.
  2019年02月, 研究論文（学術雑誌）, 共同, 31, 2, 1070-6631, DOI(公開)(r-map)
• Rheological flow models of banana peel pectin jellies as affected by sugar concentration
  Rasidek, Noor Azwani Mohd; Nordin, Mariam Firdhaus Mad; Iwamoto, Koji; Abd Rahman, Norazah; Nagatsu, Yuichiro; Tokuyama, Hideaki
  INTERNATIONAL JOURNAL OF FOOD PROPERTIES
  TAYLOR & FRANCIS INC
  In the present study, peel pectin jellies (PPJ) were isolated from banana peel Musa acuminata Colla (AAA, cv Berangan') varieties using water bath extraction; five jellies were produced, namely, PPJ_68%, PPJ_70%, PPJ_71%, PPJ_72%, and PPJ_76%. The effect of sugar content on the rheology of the PPJ and commercial fruit jelly was conducted at 25 degrees C within 0.05-100s(-1) shear rate. Flow behaviour was evaluated on the test dispersions while frequency sweeps (E-a) to obtain the viscoelastic (G' and G) were performed on the jellies. PPJ dispersion showed shear thinning flow behaviour, a good fit to the Casson model. Sugar concentration does not affect Casson parameters (K-c, K-oc, ?(ca,) and sigma(oc)). Frequency sweep decreased as viscosity increased which revealed high dependence for both G' and G. Tan for PPJ was more than unity which showed that jelly has less elastic properties. PPJ with the lowest sugar concentration, PPJ_68%, conducted at a high shear rate showed it was compatible with validation of the Cox-Merz rule.
  2018年, 研究論文（学術雑誌）, 共同, 21, 1, 1094-2912, DOI(公開)(r-map), 2087, 2099
• Motion-Based Detection of Lanthanides(III) Using Self-Propelled Droplets
  Ban, Takahiko; Sugiyama, Michiaki; Nagatsu, Yuichiro; Tokuyama, Hideaki
  JOURNAL OF PHYSICAL CHEMISTRY B
  AMER CHEMICAL SOC
  The directional and controllable transportation of self-propelled chemical objects in response to chemical signals in environmental media holds considerable promise for diverse applications. We investigated the chemotaxis of oil droplets loaded with surfactants to detect spatial gradients of lanthanide-(III) ions, among which Dy3+ and Tm3+ were the most effective chemoattractants for steering droplets toward the targets. Patterns within a chemotactic index of the lanthanide series exhibited a convex tetrad effect and a breakpoint at Gd3+. The Jorgensen-Kawabe equation, which is based on the refined spin-pairing energy theory, quantitatively demonstrated the tetrad effect. The self-propelled droplets served as a motion-based detection mechanism for lanthanides(III).
  2018年11月22日, 研究論文（学術雑誌）, 共同, 122, 46, 1520-6106, DOI(公開)(r-map), 10647, 10651
• Mechanical and metal adsorption properties of emulsion gel adsorbents composed of PEGDA-co-PEG hydrogels and tri-n-octylamine
  Tokuyama, Hideaki; Nakahata, Yu; Sato, Ryuichi; Nagatsu, Yuichiro; Ban, Takahiko
  POLYMER BULLETIN
  SPRINGER
  A novel type of emulsion gel adsorbent consisting of a polymeric hydrogel containing randomly distributed oil microdroplets of an extractant was developed for metal separation. A copolymer hydrogel composed of poly(ethylene glycol) diacrylate (PEGDA; cross-linking monomer) and polyethylene glycol (PEG), i.e., a PEGDA-co-PEG hydrogel, was developed; the hydrogel with PEGDA = 500 mol/m(3) and PEG = 50 kg/m(3) possessed improved flexibility and strength. The emulsion gel containing an amine extractant, tri-n-octylamine, successfully adsorbed Zn(II) ions. The metal-extractant complexation process and its pH dependence in the emulsion gel were comparable to those of the solvent extraction method. Investigation of the metal adsorption kinetics revealed that diffusion of the solute in the hydrogel phase is fast, and diffusion (accumulation) in the organic extractant phase is the rate-determining step.
  2018年04月, 研究論文（学術雑誌）, 共同, 75, 4, 0170-0839, DOI(公開)(r-map), 1597, 1606
• Propagating Precipitation Waves in Disordered Media
  Takahiko Ban, Masaru Kaji, Yuichiro Nagatsu, Hideaki Tokuyama
  ACS Omega
  American Chemical Society
  The study presented in this paper investigates form changes of propagating waves generated through precipitation reactions in a gel matrix that possesses an inhomogeneous microstructure. The waves demonstrate form changes from a single ring-like pattern to multiple target-like waves. Subsequently, the waves take up a spiral form and ultimately manifest themselves in the form of a turbulence pattern that intensifies with increasing fluctuations within the gel structure. An investigation into the dynamics of the precipitation waves reveals the existence of an anomalous diffusion. The effective diffusion coefficients are found to increase linearly with the quenching temperature. Further, it is revealed through the analysis of the anomalous diffusion dynamics that precipitation patterns could be adequately controlled by adjusting the permeability fluctuations within the gel structure. The findings of this study lead to a greater understanding of the spontaneous creation of precipitation patterns by a system driven by disorder.
  2017年11月16日, 研究論文（学術雑誌）, 共同, 2, 11, DOI(公開)(r-map), 8027, 8032
• Three-dimensional viscous fingering of miscible fluids in porous media
  Suekane, Tetsuya; Ono, Jei; Hyodo, Akimitsu; Nagatsu, Yuichiro
  PHYSICAL REVIEW FLUIDS
  AMER PHYSICAL SOC
  Viscous fingering is a flowinstability that is induced at the displacement front when a lessviscous fluid (LVF) displaces a more-viscous fluid (MVF). Because of the opaque nature of porous media, most experimental investigations of the structure of viscous fingering and its development in time have been limited to two-dimensional porous media or Hele-Shaw cells. In this study, we investigate the three-dimensional characteristics of viscous fingering in porous media using a microfocused x-ray computer tomography (CT) scanner. Similar to two-dimensional experiments, characteristic events such as tip-splitting, shielding, and coalescence were observed in three-dimensional viscous fingering as well. With an increase in the Pclet number at a fixed viscosity ratio, M, the fingers appearing on the interface tend to be fine; however, the locations of the tips of the fingers remain the same for the same injected volume of the LVF. The finger extensions increase in proportion to lnM, and the number of fingers emerging at the initial interface increases with M. This fact agrees qualitatively with linear stability analyses. Within the fingers, the local concentration of NaI, which is needed for the x-ray CT scanner, linearly decreases, whereas it sharply decreases at the tips of the fingers. A locally high Pclet number as well as unsteady motions in lateral directions may enhance the dispersion at the tips of the fingers. As the viscosity ratio increases, the efficiency of each sweep monotonically decreases and reaches an asymptotic state; in addition, the degree of mixing increases with the viscosity ratio. For high flow rates, the asymptotic value of the sweep efficiency is low for high viscosity ratios, while there is no clear dependence of the asymptotic value on the Peclet number.
  2017年10月, 研究論文（学術雑誌）, 共同, 2, 10, 2469-990X, DOI(公開)(r-map)
• Active Liquid Matter Driven by Nonequilibrium Interfacial Tension
  Ban, Takahiko; Kobayashi, Yuya; Suzuki, Ryuta; Nagatsu, Yuichiro
  JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
  PHYSICAL SOC JAPAN
  Many experimental studies have shown that changes in the interfacial tension trigger the self-propulsion of active liquid matter. It is widely believed that for the self-propulsion of a liquid droplet, the interfacial spontaneous convection generated by the Marangoni effect is required. However, several experimental and theoretical studies have demonstrated that the Marangoni effect has a retarding effect on the moving velocity. This contradiction has led to the investigation of alternative propulsion mechanisms. A new understanding of self-propulsion obtained by resolving the interpretation of this discrepancy is discussed in this review. Furthermore, this review summarizes the current state of experimental and theoretical research on the bifurcation of movement modes.
  2017年10月, 研究論文（学術雑誌）, 共同, 86, 10, 0031-9015, DOI(公開)(r-map)
• Self-Propelled Vesicles Induced by the Mixing of Two Polymeric Aqueous Solutions through a Vesicle Membrane Far from Equilibrium
  T. Ban, T. Fukuyama, S. Makino, E. Nawa, and Y. Nagatsu
  Langmuir
  American Chemical Society
  This study describes the development of self-propelled vesicles using transient interfacial energy in an aqueous two-phase system composed of polyethylene glycol (PEG), dextran (DEX), and water. The transient interfacial energy was generated at the mixing boundary between the PEG and DEX solutions when the two miscible liquids were in contact with each other far from equilibrium. Vesicles encapsulating 20 wt % DEX solution traveled spontaneously when the PEG concentration in the environmental media was >15 wt %. The motility of the vesicles varied with the permeability of the vesicle membrane. The permeability increased significantly when the concentration of PEG was >15 wt %. PEG had a profound effect not only on mass transfer through the membrane but also on the motility of the vesicles.
  2016年03月, 研究論文（学術雑誌）, 共同, 32, 11, DOI(公開)(r-map), 2574–2581
• Propagation Properties of the Precipitation Band in an AlCl3/NaOH System
  T. Ban, Y. Nagatsu, H. Tokuyama
  Langmuir
  American Chemical Society
  When inherently immobile solid particles collectively form precipitates in a reaction–diffusion system involving a redissolution reaction, a propagation phenomenon may occur in which a dynamic pattern of precipitation bands forms. This propagating precipitation phenomenon has been studied by many researchers. However, two completely different processes—i.e., the reaction-diffusion of reactants and the crystal growth of products—progress simultaneously in the system, thereby rendering the phenomenon complex. There are no well-established experimental laws for this propagating precipitation phenomenon, such as the spacing, time, and width laws associated with the well-known Liesegang phenomenon, which is static in the sense that precipitation bands form and remain at the same position. In fact, it has not been clarified which of the processes controls the propagation phenomenon. Accordingly, we have investigated the apparent diffusion coefficient associated with the dynamics of propagating precipitation band in an AlCl3/NaOH system for the case in which a large excess of outer electrolytes (i.e., OH–) diffuses into gel in which inner electrolytes (i.e.,Al3+) are homogeneously distributed. An isolated precipitation band of Al(OH)3 was formed horizontally in a test tube and propagated vertically in proportion to the square root of time. In our experimental results, we found that the apparent diffusion coefficient, Dp, possesses an exponential dependence on the initial concentrations of the outer electrolyte, and the inner electrolyte; the measured relation was Dp = D[Al3+]−0.6[OH–]0.6, where D = (0.63 ± 0.04) × 105 cm2/s. From our model equations based on the prenucleation theory, which take into account a redissolution reaction, we found that the dynamics of the reaction front of the outer and the inner electrolytes was an important factor in controlling the propagation of the precipitation band. In our simulation results, we obtained a similar dependence of the apparent diffusion coefficient on the electrolyte concentrations.
  2016年01月, 研究論文（学術雑誌）, 共同, 32, 2, DOI(公開)(r-map), 604, 610
• 可視化により解明した液相反応流の知見
  長津雄一郎
  可視化情報学会誌
  2015年04月, 単独, 35, 14, 19
• Viscous Fingering Phenomena with Chemical Reactions
  Y. Nagatsu
  Current Physical Chemistry
  2015年01月, 単独, 5, 52, 63
• Hydrodynamic Fingering Instability Induced by a Precipitation Reaction
  Y. Nagatsu, Y. Ishii, Y. Tada, and A. De Wit
  Physical Review Letters
  American Physical Society
  We experimentally demonstrate that a precipitation reaction at the miscible interface between two reactive solutions can trigger a hydrodynamic instability due to the buildup of a locally adverse mobility gradient related to a decrease in permeability. The precipitate results from an A+B→C type of reaction when a solution containing one of the reactants is injected into a solution of the other reactant in a porous medium or a Hele-Shaw cell. Fingerlike precipitation patterns are observed upon displacement, the properties of which depend on whether A displaces B or vice versa. A mathematical modeling of the underlying mobility profile confirms that the instability originates from a local decrease in mobility driven by the localized precipitation. Nonlinear simulations of the related reaction-diffusion-convection model reproduce the properties of the instability observed experimentally. In particular, the simulations suggest that differences in diffusivity between A and B may contribute to the asymmetric characteristics of the fingering precipitation patterns.
  2014年07月, 研究論文（学術雑誌）, 共同, 113, 2, DOI(公開)(r-map), 024502
• Experimental evidence of reaction-driven miscible viscous fingering
  L. A. Riolfo, Y. Nagatsu, S. Iwata, R. Maes, P. M. J. Trevelyan, and A. De Wit
  Physical Review E
  American Physical Society
  An experimental demonstration of reaction-driven viscous fingering developing when a more viscous solution of a reactant A displaces a less viscous miscible solution of another reactant B is presented. In the absence of reaction, such a displacement of one fluid by another less mobile one is classically stable. However, a simple A+B→C reaction can destabilize this interface if the product C is either more or less viscous than both reactant solutions. Using the pH dependence of the viscosity of some polymer solutions, we provide experimental evidence of both scenarios. We demonstrate quantitatively that reactive viscous fingering results from the buildup in time of nonmonotonic viscosity profiles with patterns behind or ahead of the reaction zone, depending on whether the product is more or less viscous than the reactants. The experimental findings are backed up by numerical simulations.
  2012年01月, 研究論文（学術雑誌）, 共同, 85, 1, DOI(公開)(r-map), 015304
• 乱流撹拌槽の撹拌所要動力に及ぼす邪魔板挿入深さの影響
  加藤禎人， 亀井登， 多田豊， 中岡梓， 伊吹竜彦， 長津雄一郎， 高承台， 李泳世
  化学工学論文集
  公益社団法人 化学工学会
  種々の撹拌翼を備えた乱流撹拌槽の撹拌所要動力に与える邪魔板挿入深さの影響を実験的に検討した．種々の翼に対する邪魔板挿入深さ，邪魔板枚数，邪魔板幅を変数とした撹拌所要動力の相関式を提案した．本相関式は邪魔板枚数が1枚のとき測定値が相関値より若干小さくなったが，おおむね良好に動力を推算することができた．特に傾斜パドル翼の動力数は平岡らの相関式（1997）を用いて相関が可能であった．
  2011年09月20日, 研究論文（学術雑誌）, 37, 5, DOI(公開)(r-map), 377, 380
• 球底乱流撹拌槽の撹拌所要動力
  加藤禎人， 塩原克己， 古川陽輝， 多田豊， 長津雄一郎， 高承台， 李泳世
  化学工学論文集
  公益社団法人 化学工学会
  これまで撹拌槽に関する研究は，平底円筒槽に関するものがほとんどであり，実機に採用されている皿底および球底槽に関するデータは少なく，スケールアップにおいて，実験室スケールの実験値と実機の実測値の差が問題点とされてきた．本報では，球底槽と皿底槽および平底槽との撹拌所要動力の差異を明らかにした．その結果，最も差が顕著に表れる撹拌槽の条件は，標準邪魔板条件の乱流状態では，パドル翼を用いたときであることがわかった．その際，球底槽の撹拌所要動力は平底槽のそれに比べて最大約27%低下した．傾斜翼およびプロペラ翼の動力数は槽底形状の影響はほとんど受けなかった．
  2011年07月20日, 研究論文（学術雑誌）, 37, 4, DOI(公開)(r-map), 305, 309
• Viscous fingering of a miscible reactive A+B →C interface for an infinite Damköhler number: Nonlinear simulations
  Y. Nagatsu and A. De Wit
  Physics of Fluids
  AIP
  Nonlinear dynamics of miscible viscous fingering is analyzed numerically for a reactive system when a solution containing a reactant A A is displacing another miscible solution containing another reactant B B . A simple A+B→C A+B→C reaction takes place upon contact of the solutions. The viscosity of the fluid depends on the concentration of the various chemicals. The nonlinear fingering dynamics is studied numerically for an infinite Damköhler number D a Da , i.e., for an infinitely fast reaction as a function of the log-mobility ratios R b Rb and R c Rc quantifying the viscosity ratios of the solutions of B B and C C , respectively, versus that of the solution of A A . If R b >0 Rb>0 , i.e., if the system is genuinely viscously unstable because the displacing solution of A A is less viscous than the displaced solution of B B , we analyze the changes to classical nonreactive viscous fingering induced by the reaction. If on the contrary R b <0 Rb<0 , which corresponds to a hydrodynamically stable case in absence of reactions, we study chemically driven viscous fingering occurring when the chemical reaction triggers a nonmonotonic viscosity profile. Comparison between the present simulation results and corresponding linear stability analysis and experiments is also conducted.
  2011年04月, 研究論文（学術雑誌）, 共同, 23, 4, DOI(公開)(r-map), 043103
• ラシュトンタービン翼を備えた乱流撹拌槽の撹拌所要動力に及ぼす邪魔板挿入深さの影響
  加藤禎人， 亀井登， 多田豊， 中岡梓， 長津雄一郎， 高承台， 李泳世
  化学工学論文集
  公益社団法人 化学工学会
  皿底および平底の乱流撹拌槽の撹拌所要動力に与える邪魔板挿入深さの影響を実験的に検討した．槽底形状によらず邪魔板挿入深さ，邪魔板枚数，邪魔板幅を変数とした撹拌所要動力の相関式を提案した．本相関式は邪魔板枚数が1枚のとき，および，翼の取り付け位置が槽底に近いとき，測定値が相関値より若干小さくなるが，おおむね良好に動力を推算することができた．
  2011年03月02日, 研究論文（学術雑誌）, 共同, 37, 2, DOI(公開)(r-map), 147, 149
• Miscible viscous fingering involving viscosity increase by a chemical reaction with moderate Damköhler number
  Yuichiro Nagatsu, Yusuke Kondo, Yoshihito Kato, and Yutaka Tada
  Physics of Fluids
  AIP
  In our previous study, we experimentally studied the effects of increased or decreased viscosity of the more-viscous liquid caused by chemical reactions at a very high Damköhler number, Da (defined as the ratio between a characteristic time of fluid motion and that of a chemical reaction), on miscible viscous fingering [Y. Nagatsu et al., “Experimental study on miscible viscous fingering involving viscosity changes induced by variations in chemical species concentrations due to chemical reactions,” J. Fluid Mech. 571, 475 (2007)]. In another study, we experimentally studied the effects of decreased viscosity caused by chemical reaction at a moderate Da on the fingering [Y. Nagatsu et al., “Effects of moderate Damköhler number on miscible viscous fingering involving viscosity decrease due to a chemical reaction,” J. Fluid Mech. 625, 97 (2009)]. In the present study, we investigated the effects of increased viscosity caused by chemical reaction at a moderate Da on the fingering in a radial Hele-Shaw cell. We observed that the present reaction decreased the area occupied by the fingering pattern around the injection hole. As a result, the fingering pattern became less dense following the reaction. The smaller the Da, the less significant the influence of the reaction on the fingering pattern. The present experimental results provide a coherent link between the results of earlier studies of miscible viscous fingering involving changes in the viscosity caused by chemical reactions.
  2011年01月, 研究論文（学術雑誌）, 共同, 23, 1, DOI(公開)(r-map), 014109
• 広いレイノルズ数領域におけるアンカー翼の撹拌所要動力
  加藤禎人， 亀井登， 多田豊， 加藤紀幸， 加藤知帆， 伊吹竜彦， 古川陽輝， 長津雄一郎
  化学工学論文集
  公益社団法人 化学工学会
  層流域から乱流域まで幅広い範囲において的確な動力相関方法のないアンカー翼の撹拌所要動力が測定された．層流域では，アンカー翼を大きなパドル翼とみなすことで，その動力数は2枚羽根パドル翼に対する永田の式，亀井らの式で十分相関できた．乱流域では，亀井らの式でパラメーターの補正を加えることなく相関できた．ただし，乱流域で回転数が大きくなり渦が発生した場合，動力数は相関値より若干大きくなるので注意が必要である．
  2011年01月20日, 研究論文（学術雑誌）, 37, 1, DOI(公開)(r-map), 19, 21
• Effect of Mixing on Sonochemical Reaction in a Sonoreactor
  Jingsong Zhou, Yutaka Tada, Yoshihito Kato, Yuichiro Nagatsu, Ryo Takebayashi, Kyoichi Iwata, Katsufumi Yasui, Yuya Sakaguchi
  Journal of chemical engineering of Japan
  The Society of Chemical Engineers, Japan
  When ultrasound is irradiated in liquid, a local reaction field with high temperature and high pressure, which is called a hot spot due to cavitation, is formed. In order to enhance the performance of a sonoreactor, it was considered to improve the liquid flow by a propeller set in the sonoreactor. With the placement position, the revolution speed and the number of blades of the propeller varied at the same liquid height and power input, a decolorization reaction of iodine in the presence of disodium hydrogenphosphate in a starch solution has been carried out in order to examine the effect of the mixing on the sonochemical reaction. The mixing by the propeller made the intrinsic chemical reaction field larger and the sonochemical reaction faster. The reaction rate became faster with an increase in the revolution speed of the propeller. At the same placement position and revolution speed, the reaction rate was much faster for a propeller with more blades.
  2010年08月20日, 研究論文（学術雑誌）, 43, DOI(公開)(r-map), 657, 660
• Viscous fingering の反応性流体力学の実験研究 (竜門賞受賞記念解説)
  長津 雄一郎
  ながれ: 日本流体力学会誌= Journal of Japan Society of Fluid Mechanics
  日本流体力学会
  2010年06月25日, （MISC）総説・解説（学術雑誌）, 単独, 29, 3, 161, 164

研究発表、招待講演等

• 2020年度化学工学会粒子・流体プロセス部会　フロンティア賞受賞記念講演 部分混和系での流体力学的に安定な置換におけるスピノーダル分解により引き起 こされるフィンガリングパターン
  化学工学会第86 年会　2020 年粒子・流体プロセス部会 部会セミナー・総会
  2021年03月21日, 口頭発表（招待・特別）
• 2019年度化学工学会粒子・流体プロセス部会　フロンティア賞受賞記念講演　化学反応前後の流体の物性値では予測できない高分子反応流の流動ダイナミクス: ATR-FTIR 分光法による分子診断を伴う流体力学
  化学工学会第86 年会　2020 年粒子・流体プロセス部会 部会セミナー・総会
  2021年03月21日, 口頭発表（招待・特別）
• 部分混和系におけるViscous fingeringの安定化
  日本機械学会 関東支部　第27期総会・講演会
  2021年03月10日, 口頭発表（一般）
• 化学反応前後の物性値では予測できない高分子溶液の流動を引き起こす条件の一般化への検討
  日本機械学会 関東支部　第27期総会・講演会
  2021年03月10日, 口頭発表（一般）
• 擬２Dケミカルガーデンパターンに関する界面レオロジーの研究
  第25回東日本支部修士発表会（関東地区修士発表会）
  2021年03月08日, 口頭発表（一般）
• 油水反応粘弾性界面を用いた新規な重質油増進回収法の創出
  令和2 年度（2020 年）石油技術協会　学術大会
  2020年10月25日, 口頭発表（一般）
• Influences of physicochemical effects on interfacial hydrodynamics
  第６回理論応用力学シンポジウム
  2020年09月02日, 口頭発表（招待・特別）
• 反応界面レオロジーを基軸とするゲル生成反応流研究の展開
  希薄溶液の流動学研究会
  2018年05月16日, 口頭発表（招待・特別）
• Influences of Physicochemical Effects on Interfacial Hydrodynamics
  14th International Conference on Flow Dynamics
  2017年11月01日, 口頭発表（招待・特別）
• 界面液体力学に及ぼす種々の物理化学効果の影響
  分離技術会2017
  2017年05月26日, 口頭発表（招待・特別）
• Influences of physicochemical effects on interfacial hydrodynamics
  9th Asian Coating Workshop 2017
  2017年05月17日, 口頭発表（招待・特別）
• CO2地中隔離への応用を指向した多孔質媒質内における多成分系および反応系流動に関する基礎研究
  平成28年度 資源・素材関係学協会合同秋季大会
  2016年09月13日, 口頭発表（招待・特別）
• Hydrodynamic Fingering Instability with Precipitation Reactions
  12th International Conference on Flow Dynamics
  2015年10月27日, 口頭発表（招待・特別）
• Reactive viscous fingering involving viscosity change
  Solvay International Workshop on Patterns and hydrodynamic instabilities in reactive systems, Solvay Institutes
  2013年05月16日, 口頭発表（招待・特別）

外部研究資金等

• 飛躍的な石油増進回収のための油水反応レオロジー界面の創成
  受託研究, 自 2016年04月01日, 至 2017年03月31日
• 飛躍的な石油増進回収のための油水反応レオロジー界面の創成
  受託研究, 自 2015年04月01日, 至 2016年03月31日
• 飛躍的な石油増進回収のための油水反応レオロジー界面の創成
  受託研究, 自 2014年04月01日, 至 2015年03月31日
• 飛躍的な石油増進回収のための油水反応レオロジー界面の創成
  受託研究, 自 2013年10月01日, 至 2014年03月31日

メディア報道

• 　
  Dr. Nagatsu have explored, for the first time, the viscous fingering (VF, one of classical interfacial hydrodynamics) of an annular ring, where 'fingers' in a fluid of finite volume grow radially, through a combination of experiment and numerical simulation.
  　
  自 2021年07月06日, 至 2021年07月06日
• 　
  The Tokyo University of Agriculture and Technology (TUAT) in association with Osaka University has proposed a novel approach for tuning hydrodynamics interfacial instability through a thermodynamic parameter to facilitate control over liquid-liquid phase separation.
  　
  自 2021年09月28日, 至 2021年09月28日
• 　
  ※アラビア語記事　東京農工大学の長津雄一郎准教授らが油田から重油成分を多く含んでいる重質油を効率よく回収できる新手法を発明したことが紹介される
  　
  自 2020年11月24日, 至 2020年11月24日
• 重質油を効率よく回収する新手法を発明 東京農工大、逆転の発想が奏功
  東京農工大学の研究グループが、油田から重油成分を多く含んでいる重質油を効率よく回収できる新手法を発明したことが紹介される。
  Science Portal／マイナビニュース／yahooニュース
  自 2020年10月30日, 至 2020年10月30日
• 　
  　
  自 2020年01月27日, 至 2020年01月27日
• 　
  An associate professor in the Department of Chemical Engineering at Tokyo University of Agriculture and Technology, and the corresponding author of the paper, Yuichiro Nagatsu,said that in other words, if a fluid property such as the viscosity of the solution is higher after the reaction than before, they would expect that an increase in viscosity occurs from the reaction during flow.
  　
  自 2019年06月27日, 至 2019年06月27日
• 　
  　
  自 2020年09月28日, 至 2020年09月28日
• 　
  　
  自 2020年09月28日, 至 2020年09月28日
• 　
  　
  自 2020年09月28日, 至 2020年09月28日
• 水と油の「部分混和系」に現れる模様のトポロジカルな変化とは？ ? 流体力学と化学熱力学の挑戦
  academist Journal
  自 2020年11月16日, 至 2020年11月16日
• 　
  　
  自 2020年11月23日, 至 2020年11月23日
• 　
  　
  自 2020年11月24日, 至 2020年11月24日
• 化学反応前後で高分子溶液の「反応流」はどう変化するか？ ? 反応系流体力学の確立を目指す
  academist Journal
  自 2021年01月28日, 至 2021年01月28日

所属学協会

• アメリカ物理学会
• 日本流体力学会
• 日本機械学会
• 化学工学会

受賞

• 2020年度 化学工学会　粒子・流体プロセス部会フロンティア賞
  2021年03月21日
• 東海化学工業会賞 学術賞
  粘性の異なる二液相流における反応輸送現象に関する研究
  2011年05月
• 名古屋工業大学
  名古屋工業大学 職員褒賞 優秀賞
  化学工学会研究奨励賞と日本流体力学会竜門賞のダブル受賞と科研費若手研究(A)採択
  2010年11月
• 日本流体力学会
  日本流体力学会 竜門賞
  Viscous fingering の反応性流体力学の実験研究
  2010年02月
• 化学工学会
  化学工学会 研究奨励賞
  粘性の異なる二液相反応流に関する研究
  2009年12月