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研究者情報

マスター

アカウント（マスター）

  • 氏名

    小林　一道(コバヤシ　カズミチ), コバヤシ　カズミチ

所属（マスター）

  • 工学研究院　機械・宇宙航空工学部門　熱流体システム

所属（マスター）

  • 工学研究院　機械・宇宙航空工学部門　熱流体システム

独自項目

syllabus

  • 2021, 流体工学特論, Advanced Fluid Engineering, 修士課程, 工学院
  • 2021, 大学院共通授業科目（一般科目）：自然科学・応用科学, Inter-Graduate School Classes(General Subject):Natural and Applied Sciences, 修士課程, 大学院共通科目, Fluid engineering, Theory of thermal-fluid mechanics, Computational fluid mechanics, Flow measurement & visualization, Food Science
  • 2021, 分子流体力学特論, Molecular Fluid Dynamics, 修士課程, 工学院, Molecular Gas Dynamicd, Boltzmann Equation, Maxwell Transport Equation, Statistical Thermodynamics
  • 2021, 流体工学特論, Advanced Fluid Engineering, 博士後期課程, 工学院
  • 2021, 分子流体力学特論, Molecular Fluid Dynamics, 博士後期課程, 工学院, Molecular Gas Dynamicd, Boltzmann Equation, Maxwell Transport Equation, Statistical Thermodynamics
  • 2021, 熱流体力学演習Ⅰ, Exercise on Thermo and Fluid Dynamics Ⅰ, 学士課程, 工学部, 各種保存則，有効エネルギー，理想気体，検査体積，運動量理論，ベルヌーイの定理，ポテンシャル流れ
  • 2021, 機械工学概論, Introduction to Mechanical Engineering, 学士課程, 工学部, 機械工学，材料，機械力学，熱，流体，エネルギー

researchmap

プロフィール情報

所属

  • 北海道大学, 大学院工学研究院, 准教授
  • 機械宇宙工学専攻

学位

  • 博士（工学）（北海道大学）

プロフィール情報

  • 姓

    小林, Kobayashi

  • 名

    一道, Kazumichi

  • ID各種

    200901052576073672

対象リソース

所属

  • 北海道大学, 大学院工学研究院, 准教授
  • 機械宇宙工学専攻

業績リスト

研究キーワード

  • 分子動力学   分子気体力学   液滴   気泡   界面相変化現象   分子流体力学   流体工学   

研究分野

  • ものづくり技術（機械・電気電子・化学工学） / 流体工学

経歴

  • 2013年04月 - 現在 北海道大学 工学研究院 准教授
  • 2015年04月 - 2015年09月 名古屋大学 大学院工学研究科 非常勤講師
  • 2010年04月 - 2013年03月 北海道大学 工学研究院 助教
  • 2007年04月 - 2010年03月 大阪府立大学 工学研究科 助教
  • 2006年04月 - 2007年03月 北海道大学 工学研究科 日本学術振興会特別研究員（DC2）

学歴

  • 2004年04月 - 2007年03月   北海道大学   大学院工学研究科   機械科学専攻 博士後期課程
  • 2002年04月 - 2004年03月   北海道大学   大学院工学研究科   機械科学専攻 修士課程
  • 1998年04月 - 2002年03月   北海道大学   工学部   機械工学科

委員歴

  • 2024年04月 - 現在   日本流体力学会   代議員
  • 2024年01月 - 現在   日本熱物性学会   評議員
  • 2023年04月 - 現在   日本機械学会   流体工学部門 運営委員
  • 2018年04月 - 現在   日本機械学会   日本機械学会論文集編修委員会 アソシエイトエディタ
  • 2022年04月 - 2024年03月   日本機械学会   流体工学部門 技術委員会 幹事
  • 2023年04月 - 2023年08月   日本混相流学会   混相流シンポジウム2023実行委員
  • 2020年04月 - 2022年03月   日本流体力学会   代議員
  • 2021年01月 - 2022年01月   第53回日本熱物性シンポジウム実行委員会   幹事
  • 2020年01月 - 2022年01月   日本熱物性学会   評議員
  • 2018年04月 - 2020年03月   日本機械学会RC277分科会   幹事
  • 2018年12月 - 2019年11月   第33回数値流体力学シンポジウム   実行委員
  • 2018年08月 - 2019年08月   日本混相流学会   評議員
  • 2017年08月 - 2019年08月   日本混相流学会   ICeM委員
  • 2016年08月 - 2019年08月   日本混相流学会   編集委員
  • 2018年04月 - 2019年03月   日本機械学会 流体工学部門   広報委員会
  • 2017年11月 - 2018年12月   第16回流れの夢コンテスト   実行委員長
  • 2017年11月 - 2018年11月   日本機械学会 第96期 流体工学部門講演会   実行委員
  • 2017年10月 - 2018年10月   第19回キャビテーションに関するシンポジウム   幹事
  • 2017年10月 - 2018年05月   第55回伝熱シンポジウム   実行委員（プログラム＆OS担当）
  • 2016年01月 - 2018年01月   日本熱物性学会   評議員
  • 2015年04月 - 2017年03月   日本機械学会   P-SCC13:マイクロ熱流動に関する調査研究分科会 委員
  • 2014年04月 - 2017年03月   日本機械学会   校閲委員
  • 2015年04月 - 2016年03月   日本機械学会北海道支部   商議員 （支部会計委員兼務）
  • 2014年04月 - 2015年09月   日本機械学会   日本機械学会2015度年次大会 実行委員
  • 2014年07月 - 2015年03月   日本機械学会   日本機械学会北海道支部 学生委員
  • 2013年09月 - 2014年07月   日本混相流学会   混相流シンポジウム2014 実行委員 総務
  • 2012年01月 - 2014年01月   日本熱物性学会   評議員
  • 2011年04月 - 2013年03月   日本機械学会北海道支部   流体工学懇話会 幹事
  • 2011年04月 - 2013年03月   日本機械学会流体工学部門   広報委員
  • 2010年04月 - 2010年09月   日本流体力学会   日本流体力学会年会2010 Web幹事

受賞

  • 2023年07月 日本機械学会 流体工学部門 フロンティア表彰
     気液界面熱物質輸送に関する分子流体力学解析 
    受賞者: 小林一道
  • 2021年04月 Nature Portfolio Top 100 in Physics
     Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions 
    受賞者: Kotaro Ohashi;Kazumichi Kobayashi;Hiroyuki Fujii;Masao Watanabe
  • 2008年04月 日本機械学会 日本機械学会賞（論文）
     衝撃波管管端でのメタノール蒸気の凝縮過程に関する分子気体力学解析
  • 2007年03月 日本熱物性学会 ベストプレゼンテーション賞
     衝撃波管管端で起こる膜状凝縮によって測定された水の凝縮係数 
    受賞者: 小林 一道
  • 2005年06月 The 1st CRIS International Symposium on Computational Science and Neuroscience Top Poster Award
     Determination of Condensation Coefficient of Methanol by Combining Molecular Gas Dynamics Simulation and Shock Tube Experiment 
    受賞者: Kazumichi Kobayashi

論文

  • Hiroyuki Fujii, Hyeonwoo Na, Jungyun Yi, Kazumichi Kobayashi, Masao Watanabe
    Colloids and Surfaces A: Physicochemical and Engineering Aspects 135208 - 135208 2024年08月
  • Hiroyuki Fujii, Hyeonwoo Na, Koyata Nishikawa, Kazumichi Kobayashi, Masao Watanabe
    Optical Review 31 3 299 - 308 2024年05月22日 
    Abstract Near-infrared spectroscopy and imaging using scattered light potentially evaluate the structural properties of the medium, like the average particle size, based on a relation between its structure and light scattering. A qualitative understanding of light scattering is crucial for developing optical imaging techniques. The scattering properties of dense colloidal suspensions have been extensively investigated using the electromagnetic theory (EMT). The colloidal suspensions are widely used in liquid tissue phantoms for optical imaging techniques and are encountered in various fields, such as the food and chemical industries. The interference between electric fields scattered by colloidal particles significantly influences the scattering properties, so-called the interference effects. Despite many efforts since the 1980s, a complete understanding of the interference effects has still not been achieved. The main reason is the complicated dependence of the interference on the optical wavelength, particle size, and so on. This paper briefly reviews numerical and theoretical studies of the interference effect based on the dependent scattering theory, one of the EMTs, and model equations.
  • Kazumichi Kobayashi, Kota Aoki, Hirofumi Tabe, Hiroyuki Fujii, Toshiki Nara, Hideyoshi Takashima, Nobuyuki Oshima, Masao Watanabe
    Physics of Fluids 35 8 082021 - 082021 2023年08月01日 [査読有り][通常論文]
     
    This paper presents molecular dynamics simulations of the Couette flow of a rarefied gas between the liquid and wall boundaries and, in particular, investigates the boundary conditions for the Boltzmann equation at the liquid interface. The simulation results for various Knudsen numbers show that the slip velocity decreases at the liquid boundary and increases at the smooth wall as the Knudsen number increases, indicating that the velocity profile of the rarefied Couette flow is asymmetric. One reason for this is backscattering, in which molecules are reflected in the opposite direction to the mainstream flow, owing to molecular-scale roughness at the liquid boundary. It has also been suggested that the backscattering effect decreases when the gas density increases. This can be understood using the local Knudsen numbers near the liquid boundary.
  • Hiroyuki Fujii, Koyata Nishikawa, Hyeonwoo Na, Yuki Inoue, Kazumichi Kobayashi, Masao Watanabe
    Infrared Physics & Technology 132 104753 - 104753 2023年08月
  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    International Communications in Heat and Mass Transfer 142 106622 - 106622 2023年03月 [査読有り][通常論文]
  • Hirofumi Tabe, Kiryu Hiramatsu, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe, Tsuyoshi Totani
    Applied Thermal Engineering 212 118472 - 118472 2022年07月 [査読有り][通常論文]
  • Ryunosuke Adachi, Kazumichi Kobayashi, Hiroyuki Fujii, Toshiyuki Sanada, Masao Watanabe
    Physics of Fluids 34 6 062116 - 062116 2022年06月 [査読有り][通常論文]
     
    A water drop impacting a dry solid surface can eject a thin liquid sheet, which is forced to expand on the surface to wet the solid surface. Wetting failure, which produces defects in applications based on the impact of drops, including coating, cooling, cleaning, and printing, may occur with a sufficiently large liquid-sheet velocity. However, the exact onset of wetting failure when a drop impacts the surface has yet to be determined. Therefore, we examine the dependence of rim instability immediately after liquid-sheet ejection on the static contact angle of the solid surface at the instant of water drop impact. This study is the first attempt to solve this problem and is made possible only by using an ultra-high-speed camera. We revealed that wetting failure can occur by investigating the rim instability of the liquid sheet.
  • Hiroyuki Fujii, Iori Terabayashi, Kazumichi Kobayashi, Masao Watanabe
    Photoacoustics 27 100368 - 100368 2022年06月 [査読有り][通常論文]
  • Hirofumi Tabe, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    International Journal of Heat and Mass Transfer 188 122663 - 122663 2022年06月01日 [査読有り][通常論文]
  • Hiroyuki Fujii, Moegi Ueno, Yuki Inoue, Toshiaki Aoki, Kazumichi Kobayashi, Masao Watanabe
    Optics Express 30 3 3538 - 3538 2022年01月31日 [査読有り][通常論文]
  • Hiroyuki Fujii, Iori Terabayashi, Toshiaki Aoki, Yuki Inoue, Hyeonwoo Na, Kazumichi Kobayashi, Masao Watanabe
    Applied Sciences 12 3 1190 - 1190 2022年01月24日 [査読有り][通常論文]
     
    Understanding light propagation in liquid phantoms, such as colloidal suspensions, involves fundamental research of near-infrared optical imaging and spectroscopy for biological tissues. Our objective is to numerically investigate light propagation in the alumina colloidal suspensions with the mean alumina particle diameter of 55 nm at the volume fraction range 1–20%. We calculated the light scattering properties using the dependent scattering theory (DST) on a length scale comparable to the optical wavelength. We calculated the steady-state radiative transfer and photon diffusion equations (RTE and PDE) using the DST results based on the finite difference method in a length scale of the mean free path. The DST calculations showed that the scattering and reduced scattering coefficients become more prominent at a higher volume fraction. The anisotropy factor is almost zero at all the volume fractions, meaning the scattering is isotropic. The comparative study of the RTE with the PDE showed that the diffusion approximation holds at the internal region with all the volume fractions and the boundary region with the volume fraction higher than 1%. Our findings suggest the usefulness of the PDE as a light propagation model for the alumina suspensions rather than the RTE, which provides accurate but complicated computation.
  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    Physics of Fluids 33 12 122017 - 122017 2021年12月22日 [査読有り][通常論文]
  • Hirofumi Tabe, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    PLOS ONE 16 3 e0248660 - e0248660 2021年03月16日 [査読有り]
     
    The kinetic boundary condition (KBC) represents the evaporation or condensation of molecules at the vapor–liquid interface for molecular gas dynamics (MGD). When constructing the KBC, it is necessary to classify molecular motions into evaporation, condensation, and reflection in molecular-scale simulation methods. Recently, a method that involves setting the vapor boundary and liquid boundary has been used for classifying molecules. The position of the vapor boundary is related to the position where the KBC is applied in MGD analyses, whereas that of the liquid boundary has not been uniquely determined. Therefore, in this study, we conducted molecular dynamics simulations to discuss the position of the liquid boundary for the construction of KBCs. We obtained some variables that characterize molecular motions such as the positions that the molecules reached and the time they stayed in the vicinity of the interface. Based on the characteristics of the molecules found from these variables, we investigated the valid position of the liquid boundary. We also conducted an investigation on the relationship between the condensation coefficient and the molecular incident velocity from the vapor phase to the liquid phase. The dependence of the condensation coefficient on the incident velocity of molecules was confirmed, and the value of the condensation coefficient becomes small in the low-incident-velocity range. Furthermore, we found that the condensation coefficient in the non-equilibrium state shows almost the same value as that in the equilibrium state, although the corresponding velocity distribution functions of the incident velocity significantly differ from each other.
  • Hiroyuki Fujii, Go Chiba, Yukio Yamada, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabe
    Journal of Computational Physics 423 109825 - 109825 2020年09月 [査読有り][通常論文]
  • Hiroyuki Fujii, Leung Tsang, Jiyue Zhu, Koki Nomura, Kazumichi Kobayashi, Masao Watanabe
    Optics Express 2020年07月10日 [査読有り][通常論文]
  • Kotaro Ohash, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    Scientific Reports 10 8143  2020年05月 [査読有り][通常論文]
  • Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    International Journal of Thermal Science 150 106203 - 106203 2020年04月 [査読有り][通常論文]
  • Taku Ashida, Masao Watanabe, Kazumichi Kobayashi, Hiroyuki Fujii, Toshiyuki Sanada
    Physical Review Fluids 5 1 2020年01月15日 [査読有り][通常論文]
  • Characteristic length and time scales of the highly forward scattering of photons in random media
    Hiroyuki Fujii, Moegi Ueno, Kazumichi Kobayashi, Masao Watanabe
    Applied Sciences 10 93  2020年 [査読有り][通常論文]
  • Kyohei Yamamoto, Kazumichi Kobayashi, Masao Watanabe, Hiroyuki Fujii, Misaki Kon, Hiroyuki Takahira
    Physical Review Fluids 4 6 063603  2019年06月 [査読有り][通常論文]
  • Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
    Heat and Mass Transfer 55 4 993 - 1003 2019年04月 [査読有り][通常論文]
  • Kazumichi Kobayashi, Takahiro Nagayama, Masao Watanabe, Hiroyuki Fujii, Misaki Kon
    Journal of Fluid Mechanics 856 1045 - 1063 2018年12月 [査読有り][通常論文]
  • Yuki Tatekura, Masao Watanabe, Kazumichi Kobayashi, Toshiyuki Sanada
    Royal Society Open Science 5  - 181101 2018年12月 [査読有り][通常論文]
  • Hiroyuki Fujii, YukioYamad, Go Chiba, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabea
    Journal of Computational Physics 2018年07月 [査読有り][通常論文]
  • Hiroyuki Fujii, Yukio Yamada, Yoko Hoshi, Shinpei Okawa, Kazumichi Kobayashi, Masao Watanabe
    Reaction Kinetics, Mechanisms and Catalysis 123 2 439 - 453 2018年04月01日 [査読有り][通常論文]
     
    Constructions of numerical schemes for solving the radiative transfer equation (RTE) are crucial to evaluate light propagation inside photocatalytic systems. We develop accurate and efficient schemes of the three-dimensional and time-dependent RTE for numerical phantoms modeling aqueous titanium dioxide suspensions, in which the anisotropy of the forward-directed scattering varies and the strength of absorption is comparable to that of scattering. To improve the accuracy and efficiency of the numerical solutions, the forward-directed phase function is renormalized in the zeroth or first order with a small number of discrete angular directions. Then, we investigate the influences of the forward-directed scattering on the numerical solutions by comparing with the analytical solutions. The investigation shows that with the anisotropy factor less than approximately 0.7 corresponding to the moderate forward-directed scattering, the numerical solutions of the RTE using the both of the zeroth and first order renormalization approaches are accurate due to the reductions of the numerical errors of the phase function. With the anisotropy factor more than approximately 0.7 corresponding to the highly forward-directed scattering, the first order renormalization approach still provides the accurate results, while the zeroth order approach does not due to the large errors of the phase function. These results suggest that the developed scheme using the first order renormalization can provide accurate and efficient calculations of light propagation in photocatalytic systems.
  • 世古和也, 小林一道, 藤井宏之, 渡部正夫
    混相流 32 1 59 - 64 2018年 [査読有り][招待有り]
  • Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
    EUROPEAN JOURNAL OF MECHANICS B-FLUIDS 64 81 - 92 2017年07月 [査読有り][招待有り]
     
    Heat and mass transfer caused by nonequilibrium phase change (net evaporation/condensation) play a major role in a vapor-liquid two-phase flow. In general, liquid temperature changes with time because of the heat and mass transfer between the vapor and liquid phases; however, a precise investigation of the transport phenomena related to this temporal evolution of liquid temperature is still lacking. The aim of this study is to examine a kinetic boundary condition, which depends on liquid temperature, for the Boltzmann equation in a vapor-liquid two-phase system with unsteady net evaporation/condensation. In this study, we confirmed whether the kinetic boundary condition follows the temporal evolution of liquid temperature attributed to unsteady net evaporation/condensation by using the molecular simulation based on mean-field kinetic theory, and then we validated the accuracy of the kinetic boundary condition by solving the initial boundary value problem of the Boltzmann equation in unsteady net evaporation/condensation. These results showed that the kinetic boundary condition follows the temporal evolution of liquid temperature in the simulation setting of this study. Furthermore, we concluded that the kinetic boundary condition that depends on liquid temperature is guaranteed to be accurate even in unsteady net evaporation/condensation by considering the temporal evolution of liquid temperature. (C) 2016 Elsevier Masson SAS. All rights reserved.
  • H. Fujii, Y. Yamada, K. Kobayashi, M. Watanabe, Y. Hoshi
    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 33 5 2017年05月 [査読有り][通常論文]
     
    Diffuse optical tomography using near-infrared light in a wavelength range from 700 to 1000nm has the potential to enable non-invasive diagnoses of thyroid cancers; some of which are difficult to detect by conventional methods such as ultrasound tomography. Diffuse optical tomography needs to be based on a physically accurate model of light propagation in the neck, because it reconstructs tomographic images of the optical properties in the human neck by inverse analysis. Our objective here was to investigate the effects of three factors on light propagation in the neck using the 2D time-dependent radiative transfer equation: (1) the presence of the trachea, (2) the refractive-index mismatch at the trachea-tissue interface, and (3) the effect of neck organs other than the trachea (spine, spinal cord, and blood vessels). There was a significant influence of reflection and refraction at the trachea-tissue interface on the light intensities in the region between the trachea and the front of the neck surface. Organs other than the trachea showed little effect on the light intensities measured at the front of the neck surface although these organs affected the light intensities locally. These results indicated the necessity of modeling the refractive-index mismatch at the trachea-tissue interface and the possibility of modeling other neck organs simply as a homogeneous medium when the source and detectors were far from large blood vessels.
  • Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
    MICROFLUIDICS AND NANOFLUIDICS 21 3 1 - 13 2017年03月 [査読有り][通常論文]
     
    Using molecular dynamics simulations, the present study investigated the precise characteristics of the binary mixture of condensable gas (vapor) and noncondensable gas (NC gas) molecules creating kinetic boundary conditions (KBCs) at a gas-liquid interface in equilibrium. We counted the molecules utilizing the improved two-boundary method proposed in previous studies by Kobayashi et al. (Heat Mass Trans 52: 1851-1859, 2016. doi: 10.1007/s00231-015-1700-6). In this study, we employed Ar for the vapor molecules, and Ne for the NC gas molecules. The present method allowed us to count easily the evaporating, condensing, degassing, dissolving, and reflecting molecules in order to investigate the detailed motion of the molecules, and also to evaluate the velocity distribution function of the KBCs at the interface. Our results showed that the evaporation and condensation coefficients for vapor and NC gas molecules decrease with the increase in the molar fraction of the NC gas molecules in the liquid. We also found that the KBCs can be specified as a function of the molar fraction and liquid temperature. Furthermore, we discussed the method to construct the KBCs of vapor and NC gas molecules.
  • Kazumichi Kobayashi, Kazumasa Hori, Misaki Kon, Kiyofumi Sasaki, Masao Watanabe
    HEAT AND MASS TRANSFER 52 9 1851 - 1859 2016年09月 [査読有り][通常論文]
     
    Using molecular dynamics simulations, the present study investigates the precise characteristics of evaporating and reflecting monatomic molecules (argon) composing a kinetic boundary condition (KBC) in a vapor-liquid equilibria. We counted the evaporating and reflecting molecules utilizing two boundaries (vapor and liquid boundaries) proposed by the previous studies (Meland et al. in Phys Fluids 16:223-243, 2004; Gu et al. in Fluid Phase Equilib 297:77-89, 2010). In the present study, we improved the method using the two boundaries incorporating the concept of the spontaneously evaporating molecular mass flux. The present method allows us to count the evaporating and reflecting molecules easily, to investigate the detail motion of the evaporating and reflecting molecules, and also to evaluate the velocity distribution function of the KBC at the vapor-liquid interface, appropriately. From the results, we confirm that the evaporating and reflecting molecules in the normal direction to the interface have slightly faster and significantly slower average velocities than that of the Maxwell distribution at the liquid temperature, respectively. Also, the stall time of the reflecting molecules at the interphase that is the region in the vicinity of the vapor-liquid interface is much shorter than those of the evaporating molecules. Furthermore, we discuss our method for constructing the KBC that incorporates condensation and evaporation coefficients. Based on these results, we suggest that the proposed method is appropriate for investigating KBC in various nonequilibrium states or multi-component systems.
  • Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
    INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 99 317 - 326 2016年08月 [査読有り][通常論文]
     
    For the accurate description of heat and mass transfer through a vapor-liquid interface, the appropriate modeling of the interface during nonequilibrium phase change (net evaporation/condensation) is a crucial issue. The aim of this study is to propose a microscopic interfacial model which should be imposed at the interface as the kinetic boundary condition for the Boltzmann equation. In this study, we constructed the kinetic boundary condition for monoatomic molecules over a wide range of liquid temperature based on mean field kinetic theory, and we validated the accuracy of the constructed kinetic boundary condition by solving the boundary value problem of the Boltzmann equation. These results showed that we can impose the kinetic boundary condition at the interface by simply specifying liquid temperature and simulate the complex vapor-liquid two-phase flow induced by net evaporation/condensation. Furthermore, we applied the constructed kinetic boundary condition to the boundary condition for the fluid-dynamic type equations. This application enables us to deal with a large spatio-temporal scale of the interfacial dynamics in the vapor-liquid two-phase system with net evaporation/condensation. (C) 2016 Elsevier Ltd. All rights reserved.
  • Kazumichi Kobayashi, Kazuki Konno, Hisao Yaguchi, Hiroyuki Fujii, Toshiyuki Sanada, Masao Watanabe
    PHYSICS OF FLUIDS 28 3  - 032002 2016年03月 [査読有り][通常論文]
     
    In this study, we investigated nanodroplet spreading at the early stage after the impact using molecular dynamics simulations by changing the magnitude of the intermolecular force between the liquid and wall molecules. We showed that the droplet deformation after the impact greatly depends on the intermolecular force. The temporal evolution of the spreading diameters was measured by the cylindrical control volume for several molecular layers in the vicinity of the wall. At the early stage of the nanodroplet impact, the normalized spreading radius of the droplet is proportional to the square root of the normalized time, (t) over cap. This result is understood by the geometrical consideration presented by Rioboo et al. ["Time evolution of liquid drop impact onto solid, dry surfaces," Exp. Fluids 33, 112-124 (2002)]. In addition, we found that as the intermolecular force between the liquid and wall becomes stronger, the normalized spreading diameter of the first molecular layer on the wall remains less dependent on the impact velocity. Furthermore, the time evolution of the droplet spreading changes from root(t) over cap to log (t) over cap with time. (C) 2016 AIP Publishing LLC.
  • 今 美沙紀, 小林 一道, 佐々木 清文, 渡部 正夫
    混相流 29 5 493 - 500 日本混相流学会 2016年03月 [査読有り][招待有り]
     
    The aim of this study is to confirm the existence of a spontaneous evaporation molecular mass flux which takes a constant value independent of the degree of net evaporation/condensation. We carried out the numerical simulation based on the mean field kinetic theory during net evaporation/condensation and estimated the evaporation and reflection molecular mass fluxes by using a pair of boundaries. The simulation results showed that the reflection molecular mass flux varies with the increase of the degree of nonequilibrium, and the evaporation molecular mass flux takes a constant value during net evaporation and condensation.
  • Junya Kawahara, Masao Watanabe, Kazumichi Kobayashi
    Journal of Physics: Conference Series 656 012023 - 012023 2015年12月03日 [査読有り][通常論文]
     
    Pressure wave propagation in a liquid containing several bubbles is numerically investigated. We simulate liner plane wave propagation in a liquid containing 10 spherical bubbles in a rectangular duct with the equation of motion for N spherical bubbles. The sound pressures of the reflected waves from the rigid walls are calculated by using the method of images. The result shows that the phase velocity of the pressure wave propagating in the liquid containing 10 spherical bubbles in the duct agrees well with the low-frequency speed of sound in a homogeneous bubbly liquid.
  • Y Jinbo, K Kobayashi, M Watanabe, H Takahira
    Journal of Physics: Conference Series 656 012021 - 012021 2015年12月03日 [査読有り][通常論文]
     
    The ghost fluid method is improved to include heat and mass transfer across the gas-liquid interface during the bubble collapse in a compressible liquid. This transfer is due to both nonequilibrium phase transition at the interface and diffusion of the noncondensable gas across the interface. In the present method, the ghost fluids are defined with the intention of conserving the total mass, momentum, and energy, as well as the mass of each component while considering the heat and mass fluxes across the interface. The gas phase inside the bubble is a mixture of vapor and noncondensable gas, where binary diffusion between the mixture components is taken into account. The gas diffusion in the surrounding liquid is also considered. This method is applied to a simulation of a single spherical bubble collapse with heat and mass transfer across the interface in a compressible liquid. When noncondensable gas is present, it accumulates near the interface due to vapor condensation, thereby preventing further condensation. This results in a weaker bubble collapse than the case without noncondensable gas.
  • Junya Kawahara, Masao Watanabe, Kazumichi Kobayashi
    Mechanical Engineering Letters 1 115-00464 - 15-00464 2015年12月 [査読有り][通常論文]
  • 加藤昌也, 渡部正夫, 小林一道, 真田俊之
    混相流 28 5 531 - 536 2015年03月 [査読有り][招待有り]
  • Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9792 2015年 [査読有り][通常論文]
     
    An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis.
  • Y. Tatekura, T. Fujikawa, Y. Jinbo, T. Sanada, K. Kobayashi, M. Watanabe
    ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 4 9 N117 - N123 2015年 [査読有り][通常論文]
     
    A two-fluid spray cleaning technique has been gaining popularity as a cleaning process in the semiconductor industry. The most essential physical process in this technique is the impact of droplets with a velocity of O(10 m/s) on a solid surface. This study aims to experimentally and numerically investigate water-droplet impacts with velocities of up to 50 m/s and their subsequent flow fields, especially the gas flow field in the strictly limited area in the vicinity of the contact line. First, we experimentally evaluated the velocity of the splash and numerically calculated the gas velocities. Comparison of these velocities supported our assumption that the maximum gas velocity may be on approximately the same order as the velocity of the splash. Therefore, we concluded that the gas velocity field of the order of 500 m/s indeed develops at the impact of droplet with a velocity of the order of 50 m/s. Moreover, we determined that the gas pressure was of the order of 1.0 MPa by numerical analysis. Such a high pressure leads to shock wave propagation, which can contribute to the cleaning process in semiconductor production. (C) 2015 The Electrochemical Society. All rights reserved.
  • Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
    PHYSICS OF FLUIDS 26 7  - 072003 2014年07月 [査読有り][通常論文]
     
    The aim of the present study is to develop the method of determining the kinetic boundary condition (KBC) at a vapor-liquid interface in net evaporation/condensation. We proposed a novel method for determining the KBC by combining the numerical simulations of the mean field kinetic theory and the molecular gas dynamics. The method was evaluated on steady vapor flow between two liquid slabs at different temperatures. A uniform net mass flux in the vapor phase induced by net evaporation and condensation is obtained from the numerical simulation of the mean field kinetic theory for both vapor and liquid phases. The KBC was specified by using the uniform net mass flux, and the numerical simulation of the molecular gas dynamics was conducted for the vapor phase. Comparing the macroscopic variables in the vapor phase obtained from both numerical simulations, we can validate the KBC whether the appropriate solutions are obtained. Moreover, the evaporation and condensation coefficients were estimated uniquely. The results showed that the condensation and evaporation coefficients were identical and constant in net evaporation. On the other hand, in net condensation, the condensation coefficient increased with the collision molecular mass flux. We also presented the applicable limit of the KBC which is assumed to be the isotropic Gaussian distribution at the liquid temperature. From these results, the KBCs in net evaporation and condensation, which enable the exact macroscopic variables to be determined, were proposed. (C) 2014 AIP Publishing LLC.
  • 小林一道, 毛利信吾, 渡邉優介, 渡部正夫, 藤川重雄
    Netsu Bussei 27 1 9 - 14 JAPAN SOCIETY OF THERMOPHYSICAL PROPERTIES 2013年01月 [査読有り][通常論文]
     
    衝撃波管内で蒸気中を伝播する衝撃波が管端で反射した際に管端面で生ずる膜状凝縮について，液膜の成長速度を光多重反射干渉計で測定し，測定結果を分子気体力学で解析することにより，常温でのメタノールの蒸発係数及び凝縮係数を決定した．測定は気液界面での蒸気の非平衡度σ/ρ*が1≤σ/ρ*<1.3の範囲でなされた．その結果，凝縮係数は気液界面での蒸気の非平衡度が1≤σ/ρ*<1.05の領域では蒸発係数（＝0.86）とほぼ同じ値をとること，σ/ρ*＞1.05の領域では非平衡度の増大とともに蒸発係数よりも小さくなっていくこと，さらに著者らが用いてきた気体論境界条件はσ/ρ*<1.05の領域で有効であることを明らかにした．
  • 稲葉匡司, 矢野猛, 小林一道, 渡部正夫
    ながれ 31 6 487 - 490 日本流体力学会 2012年12月25日 [査読無し][通常論文]
  • 真田俊之, 橋本健太郎, 林田充司, 小林 一道, 渡部正夫
    混相流 26 2 172 - 177 THE JAPANESE SOCIETY FOR MULTIPHASE FLOW 2012年 [査読有り][通常論文]
     
    We have been developing a novel surface cleaning technique using steam and water mixed spray. Our technique shows great efficiency in removing thin surface film such as photo-resist film. However, the film-removal mechanism has not been clarified yet. One possible film-removal mechanism is the local heat expansion due to the difference of coefficients of linear expansion between film and substrate. In this study, we studied the removal characteristics of deposited aluminum film on a glass surface by spraying steam-water or air-water mixed spray. The surface temperature changes caused by the spray were carefully measured. We found that the steam and water mixed spray that increases the surface temperature can remove the film while the air and water mixed spray cannot. These results indicate that the difference of coefficients of linear expansion between film and substrate may not be the dominant factor in the film removal by the steam and water mixed spray.
  • 櫻井泰貴, 小林一道, 藤川俊秀, 真田俊之, 渡部正夫
    混相流 26 2 164 - 171 2012年 [査読有り][通常論文]
  • Toshihide Fujikawa, Yuuki Tatekura, Kazumichi Kobayashi, Toshiyuki Sanada, Atsushi Hayashida, Masao Watanabe
    ECS Transactions 41 5 67 - 74 2011年10月04日 [査読有り][通常論文]
     
    In the steam-water mixed spray-cleaning technique, droplet impact on the solid surface is the one of the primarily important physical processes. We experimentally studied a droplet impact on a solid plate that moves with a speed ranging from 1 to 50 m/s using high-speed video camera. We observed that high-speed liquid film flows radially outward along the surface just after the impact. In addition, we also observed that liquid turns into corona splash in the cases of higher impact velocities. These flows with large velocities can generate huge shear stress on the solid surface, which may contribute to cleaning. Furthermore, we numerically studied the velocity field development and found that gas flow also spreads obliquely upward. The obliquely upward flow field may also contribute in advecting removed particles or stripped resists away from the original place.
  • Kazumichi Kobayashi, Tetsuya Kodama, Hiroyuki Takahira
    Physics in Medicine and Biology 56 19 6421 - 6440 2011年10月 [査読有り][通常論文]
     
    Archive(HUSCAP)-> http://hdl.handle.net/2115/47143
  • 田中佑樹, 小林一道, 高比良裕之
    混相流 24 5 559 - 566 日本混相流学会 2011年03月 [査読有り][招待有り]
  • 小林一道, 神保佳典, 高比良裕之
    日本機械学会論文集 (B編) 77 773 20 - 32 2011年01月 [査読有り][通常論文]
  • 神保佳典, 高比良裕之, 小林一道, 安田章宏
    日本機械学会論文集 (Ｂ編) 76 762 230 - 238 2010年 [査読有り][通常論文]
     
    A fast simulation method is proposed for underwater explosion. In the method, the motion of a bubble generated by the underwater explosion is modeled with a point source and a doublet the source and doublet represent the radial motion and translational of the bubble, respectively. The bubble motions are solved coupling with the motions of free surface and a floating body by using the boundary element method (BEM). The growth and collapse of a bubble under a floating body is simulated with the present method. It is shown that the present results are in qualitative agreement with those obtained from the BEM without the bubble model in which the interfacial motion of a bubble is solved directly with the BEM. The present simulation is found to be about six times faster than the BEM simulation without the bubble model.
  • 神保佳典, 高比良裕之, 小林一道, 安田章宏
    日本機械学会論文集 (Ｂ編) 76 762 219 - 229 2010年 [査読有り][通常論文]
     
    The growth and collapse of a bubble under a floating body are simulated by using the boundary element method with linear elements to predict the damage of ship bodies induced by underwater explosion. The three-dimensional deformation of the bubble, the translation and rotation of the floating body, and the motion of water surface are taken into account in the simulation. It is shown that the bubble deforms three-dimensionally, and the liquid jet threads the bubble due to the interactions among the bubble, the floating body, and the water surface the directions of the bubble translation and the liquid jet depend on the initial location of the bubble. The Kelvin impulse is found to be useful in evaluating the translational motion of the bubble. Also, the horizontal translational motion of the bubble is much dependent on the rotational motion of a floating body when the moment of inertia of the floating body is small, the largest horizontal translation is realized between the axis of flotation and the edge of the floating body. It is also shown that there exists an initial horizontal bubble location where the moment of force acting on the floating body has the maximum value.
  • An optical interferometer for measurement of the condensation rate of a vapor in a vapor-liquid nonequilibrium state
    Kazumichi Kobayashi, Shigeo Fujikawa
    Handbook of Interferometers: Research, Technology and Applications 605 - 614 2009年11月05日 
    This chapter provides a review on an optical interferometer for fine measurement of the condensation rate of a vapor on the endwall surface of the vapor-filled low-pressure section of a shock tube. The interferometer, the original idea of which was proposed by Fujikawa et al. [1, 2], is an optical system composed of a liquid film formed on the endwall surface, the transparent endwall made of quartz glass, and physical and reference light beams. The reference beam is used to eliminate systematic noises from the physical one. Measurements of the time evolution in thickness of the liquid film for water or methanol demonstrate that it is obtained with a sufficient accuracy. From the time evolution and the theoretical counterpart based on the Gaussian-BGK Boltzmann equation, values of the condensation coefficient, an unknown parameter involved in the kinetic boundary condition at the vapor-liquid interface, are determined for water and methanol.
  • Hiroyuki Takahira, Kazumichi Kobayashi, Takahi Matsuno
    International Journal of Emerging Multidisciplinary Fluid Sciences 1 2 85 - 99 2009年06月01日 [査読有り][通常論文]
     
    The present study is concerned with the material damage of the liquid-mercury target systems induced by bubble collapse. The interaction of an incident strong shock wave with an initially spherical bubble near a glass wall in mercury is simulated using an improved Ghost Fluid Method (GFM), in which Riemann solutions are utilized to correct the values at boundary nodes. The mercury and glass are evaluated by using the equation of state for stiffened gas. The axi-symmetric motions of three phases for air, mercury, and glass are solved directly coupling the GFM with the level set method. The interaction of the shock wave with the bubble leads to the bubble deformation and the formation of liquid-jet during the collapse. The strong shock waves are generated in the mercury not only when the bubble rebounds but also when the liquid-jet impacts downstream surface of the bubble. It is shown that the impact of the shock waves on the glass wall leads to the formation of depression of the glass surface the toroidal bubble formed after the impact of liquid-jet penetrates into the depression. The present results for the axi-symmetric bubble collapse are compared with those for the two-dimensional cylindrical bubble collapse. The stronger shock waves are generated when the axi-symmetric bubble collapses, which results in the higher impulsive pressure at the glass wall and the deeper depression of the glass surface.
  • Kazumichi Kobayashi, Shunsuke Watanabe, Daigo Yamano, Takeru Yano, Shigeo Fujikawa
    FLUID DYNAMICS RESEARCH 40 7-8 585 - 596 2008年07月 [査読有り][通常論文]
     
    The condensation coefficient of water at a vapor-liquid interface is determined by combining shock tube experiments and numerical simulations of the Gaussian-BGK Boltzmann equation. The time evolution in thickness of a liquid film, which is formed on the shock tube endwall behind the shock wave reflected at the endwall, is measured with an optical interferometer consisting of the physical beam and the reference one. The reference beam is utilized to eliminate systematic noises from the physical beam. The growth rate of the film is evaluated from the measured time evolution and it is incorporated into the kinetic boundary condition for the Boltzmann equation. From a numerical simulation using the boundary condition, the condensation coefficient of water is uniquely deduced. The results show that, in a condition of weak condensation near a vapor-liquid equilibrium state, the condensation coefficient of water is almost equal to the evaporation coefficient estimated by molecular dynamics simulations near a vapor-liquid equilibrium state and it decreases as the system becomes a nonequilibrium state. The condensation coefficient of water is nearly identical with that of methanol [Mikami, S., Kobayashi, K., Ota, T., Fujikawa, S., Yano, T., Ichijo, M., 2006. Molecular gas dynamics approaches to interfacial phenomena accompanied with condensation. Exp. Therm. Fluid Sci. 30, 795-800]. (c) 2008 The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.
  • S. Mikami, K. Kobayashi, T. Ota, S. Fujikawa, T. Yano, M. Ichijo
    EXPERIMENTAL THERMAL AND FLUID SCIENCE 30 8 795 - 800 2006年08月 [査読有り][通常論文]
     
    This paper deals with the condensation coefficient of methanol, which is evaluated from a condensation rate at the vapor-liquid interface. Film condensation is induced on the endwall of a vapor-filled shock tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The liquid film grows with the lapse of time. The evolution in time of the liquid film thickness is measured by an optical interferometer with a high accuracy, and thereby the net condensation mass flux at the interface is obtained. The mass flux is incorporated into the kinetic boundary condition (KBC) at the interface for the Gaussian-BGK Boltzmann equation. Such a treatment of the boundary condition makes it possible to formally eliminate the evaporation and condensation coefficients in KBC and to obtain the unique numerical solution of the vapor-liquid system. In this way, the instantaneous condensation coefficient is accurately evaluated from the conformity with experiment and numerical solution. It is found that the values of condensation coefficient are, near vapor-liquid equilibrium states, close to those evaluated by molecular dynamics simulations. (C) 2006 Published by Elsevier Inc.
  • 日本機械学会論文集
    矢野猛, 小林一道, 藤川重雄 71 702 428 - 435 2005年 [査読有り][通常論文]
     
    Film condensation phenomenon of methanol vapor at the endwall of a shock tube behind a reflected shock wave is studied by combining a shock tube experiment with a numerical analysis based on molecular gas dynamics. The present method of analysis utilizes the Gaussian-BGK Boltzmann equation, which is applicable to a strong condensation of polyatomic gases, and thereby some restrictions included in our previous method of analysis are removed. The result shows that the condensation cofficient is nearly unity when the ratio of the vapor pressure to the saturated vapor pressure at the interface is close to unity, and it decreases with the increase of the pressure ratio. Furthermore, the relations between the vapor condition and the condensation coefficient are extended to the second order so that it may contain the effect of moderately strong condensation and that of polyatomic molecules.
  • S Fujikawa, T Yano, K Kobayashi, K Iwanami, M Ichijo
    EXPERIMENTS IN FLUIDS 37 1 80 - 86 2004年07月 [査読有り][通常論文]
     
    This paper deals with a molecular gas-dynamics method applied to the accurate determination of the condensation coefficient of methanol vapor. The method consisted of an experiment using a shock tube and computations using a molecular gas-dynamics equation. The experiments were performed in such situations where the shift from a vapor-liquid equilibrium state to a nonequilibrium one is realized by a shock wave in a scale of molecular mean free time of vapor molecules. The temporal evolution in thickness of a liquid film formed on the shock-tube endwall behind a reflected shock wave is measured by an optical interferometer. By comparing the measured liquid-film thickness with numerical solutions for a polyatomic version of the Gaussian-BGK model of the Boltzmann equation, the condensation coefficient of methanol vapor is accurately determined in vapor-liquid nonequilibrium states. As a result, it is clear that the condensation coefficient is just unity very near to an equilibrium state, but is smaller far from the equilibrium state.
  • Takeru Yano, Kazumichi Kobayashi, Shigeo Fujikawa
    Proceedings of the ASME/JSME Joint Fluids Engineering Conference 1 1457 - 1462 2003年 
    A semi-infinite expanse of a polyatomic vapor bounded by its condensed phase is considered. The condensed phase is a thin liquid film on a solid wall of finite thickness. An incident shock wave is reflected at the liquid film, and thereby the pressure behind the reflected shock exceeds the saturated pressure. Then, the vapor begins to condense onto the surface of the liquid film. We present the results of numerical study of the behavior of vapor and the growth rate of liquid film based on the kinetic theory, the Gaussian-BGK model of the Boltzmann equation with a kinetic boundary condition of a mixed type including the condensation coefficient. It is shown that both the behavior of vapor and the growth rate of liquid film are considerably affected by values of the condensation coefficient. The numerical results are also compared with those by a previous theory.

MISC

書籍等出版物

  • 蒸発・凝縮を伴う球形気泡の崩壊現象における凝縮係数の影響
    S. Morikawa, Y. Tatekura, K. Kobayashi, H. Fujii, M. Watanabe, K. Sasaki (担当:共著)
    日本流体力学会 「ながれ」 2017年05月 105-108 
    ながれ NAGARE 36
  • Liquid temperature dependence of kinetic boundary condition at vapor–liquid interface
    Misaki Kon, Kazumichi Kobayashi, Masao Watanabe (担当:共著)
    Advanced in Engineering 2017年03月 
    https://advanceseng.com/mechanical-engineering/liquid-temperature-dependence-kinetic-boundary-condition-vapor-liquid-interface/
  • 北海道大学大学院工業研究院 機械宇宙工学部門 流体力学研究室
    渡部正夫, 小林一道, 藤井宏之 (担当:共著)
    混相流 Vol.30 No.4 日本混相流学会 2016年12月
  • 気液界面での質量・運動量・エネルギーの輸送 ―分子動力学，分子気体力学，実験の融合― 第5章 蒸発・凝縮の衝撃波管による実験
    小林一道, 藤川重雄 (担当:共著)
    日本流体力学会，ながれ 2014年12月 543-548 
    ながれ Nagare 33
  • 日本混相流学会 混相流シンポジウム２０１４ 報告
    村井祐一, 小林一道 
    混相流 Vol.28 No.4 日本混相流学会 2014年12月 4
  • 気液界面での質量・運動量・エネルギーの輸送 ―分子動力学，分子気体力学，実験の融合― 第4章 蒸発・凝縮への分子気体力学の適用
    小林一道, 藤川重雄 (担当:共著)
    日本流体力学会，ながれ 2014年10月 453-459 
    ながれ NAGARE 33
  • 気液界面ダイナミクスのマルチスケール解析
    小林一道 
    えんじにあRing 北海道大学工学研究院・工学院 広報誌 2013年10月 1 
    https://www.eng.hokudai.ac.jp/engineering/2013-10/index.html
  • 相互作用を考慮した球形気泡離散モデルの解析（気泡流の音響特性）
    川原潤也, 小林一道, 渡部正夫 
    京都大学数理解析研究所講究録 2013年
  • 蒸発・凝縮をともなう非線形共鳴音波
    稲葉匡司, 矢野猛, 小林一道, 渡部正夫 (担当:共著)
    日本流体力学会，ながれ 2012年12月 487-490 
    ながれ NAGARE 31
  • 流体物理洗浄の概要と水蒸気二流体ジェットでの適用例
    真田俊之, 小林一道, 林田充司 (担当:共著)
    産業洗浄 2012年 14-19
  • 気泡力学へのGhost Fluid法の適用
    高比良裕之, 小林一道 
    日本機械学会 流体工学部門 ニューズレター「流れ」9月号 2009年 
    http://www.jsme-fed.org/newsletters/2009_9/no5.html#ctop
  • Handbook of Interferometers: Research, Technology and Application
    Nova Science Publishers 2009年 (ISBN: 9781607410508)

講演・口頭発表等

  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    AJK-FED 2023 2023年07月 口頭発表（一般）
  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    32nd International Symposium on Rarefied Gas Dynamics 2022年07月 口頭発表（一般）
  • Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
    Pre-RGD32 Online Workshop on Recent Hot Topics in Rarefied Gas Dynamics 2021年07月 口頭発表（一般）
  • Numerical simulation of vapor bubble collapse with a small amount of non-condensable gas based on molecular gas dynamics  [招待講演]
    Kazumichi Kobayashi
    Japan-Korea CFD Workshop 2019年11月 口頭発表（招待・特別）
  • Surrounding gas-independent splash at high-velocity drop impact with a projected smooth solid surface  [通常講演]
    M. Watanabe, T. Ashida, K. Kobayashi, H. Fujii, T. Sanada
    The 72nd Annual Meeting of the American Physical Society’s Division of Fluid Dynamics 2019年11月 口頭発表（一般）
  • Molecular Dynamics Study on Influence of Liquid-solid Intermolecular Force on Levitating Mechanism of Impacting Nanodroplet on Heated Wall  [通常講演]
    H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe
    Surface Wettability Effects on Phase Change Phenomena(SWEP) 2019年06月 ポスター発表
  • Molecular Gas Dynamics Analysis of Vapor-Gas Flow inside Collapsing Bubble  [通常講演]
    K. Yamamot, K. Kobayashi, H. Fujii, M. Watanabe, M. Kon, H. Takahira
    31th International Symposium on Rarefied Gas Dynamics (RGD31) 2018年07月 口頭発表（一般）
  • Influence of Surface Roughness of High Temperature Wall on Levitation of Impacting Droplet Based on Molecular Dynamics Simulation  [通常講演]
    H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe
    Surface Wettability Effects on Phase Change Phenomena(SWEP) 2018年05月 ポスター発表 
    SWEP BOOK of Abstract, p. 27
  • Molecular Dynamics Study of Droplet Impact on High-Temperature Wall  [通常講演]
    H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe
    The 7th East Asia Mechanical and Aerospace Engineering Workshop 2017年11月 口頭発表（一般） 
    1 page
  • Numerical Investigation of Light and Pressure Propagation in Biological Tissue for Model-Based Photoacoustic Tomography  [通常講演]
    K. Tabayashi, H. Fujii, K. Kobayashi, M. Watanabe
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-1526, 4 pages
  • Numerical and Experimental Analysis of Droplet Impact in Vapor Environment  [通常講演]
    S. Sawai, T. Isono, H. Fujii, K. Kobayashi, M. Watanabe, T. Sanada
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-1491, 5 pages
  • Does Chemical Properties of Solid Surface Cause Liquid Film Flow Instability at Droplet Impact?  [通常講演]
    S. Tanimoto, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-­1334, 4 pages
  • Observation of Splash Generated Immediately After the Impact of a High-Speed Droplet in Reduced-Pressure  [通常講演]
    T. Ashida, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-­1485, 4 pages
  • Micro-Droplets Generation Induced by Interactions Between Focused Ultrasound and a Liquid Surface  [通常講演]
    K. Seko, K. Kobayashi, H. Fujii, M. Watanabe
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-1173, 3 pages
  • Molecular Dynamics Simulation of the Role of the Wettability in the Droplet Impact on a High-Temperature Wall  [通常講演]
    H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe
    The Ninth JSME-KSME Thermal and Fluids Engineering Conference 2017年10月 口頭発表（一般） 
    TFEC9-1492, 4 pages
  • 気液界面での熱･物質輸送を考慮したマイクロバ ブル崩壊現象の分子流体力学解析  [招待講演]
    小林 一道
    日本機械学会年次大会2017 2017年09月 口頭発表（招待・特別） 
    【招待講演】
  • 蒸気雰囲気中の液滴衝突に関する実験・分子流体力学解析  [招待講演]
    小林 一道
    若手研究者夏季セミナー（混相流シンポジウム2017） 2017年08月 口頭発表（招待・特別） 
    【招待講演】
  • Numerical simulation of spherical vapor-gas bubble collapse  [招待講演]
    Kazumichi Kobayashi, Misaki Kon, Takahiro Nagayama, Hiroyuki Fujii, Masao Watanabe, Hiroyuki Takahirav
    Japan-U.S. Seminar on Two-Phase Flow Dynamics 2017年06月 口頭発表（招待・特別） 
    【招待講演】
  • Numerical simulation of pressure generated at the liquid droplet impact on a solid surface  [通常講演]
    Y. Tatekura, M. Watanabe, K. Kobayashi, T. Sanada
    The 3rd International Conference on Numerical Methods in Multiphase Flows 2017年06月 口頭発表（一般） 
    B62, 2 pages
  • Quantitative Method to Determine the Optical Properties of Melons by the Photon Diffusion Equation  [通常講演]
    K. Hattori, H. Fujii, G. Nishimura, K. Kobayashi, M. Watanabe
    The 5th Asian NIR Symposium 2016年11月 口頭発表（一般）
  • Optical properties of melons determined by an analysis based on the photon diffusion equation  [通常講演]
    K. Hattori, H. Fujii, G. Nishimura, K. Kobayashi, M. Watanabe
    1st Food Chemistry Conference 2016年10月 口頭発表（一般）
  • 気液界面のナノスケール熱流体力学  [招待講演]
    小林 一道
    日本機械学会2016年度年次大会 流体工学部門企画 複雑流動現象の解析技術と学理構築 （Ⅰ マイクロ流れ，分子流，機能性流体） 2016年09月 口頭発表（招待・特別） 九州大学伊都キャンパス 日本機械学会
     
    【招待講演】
  • Misaki Kon, Kobayashi Kobayashi, Masao Watanabe
    The 30th International Symposium on Rarefied Gas Dynamics 2016年07月 口頭発表（一般） University of Victoria Victoria BC Canada 
    AIP Conf. Proc., Vol. 1786, 110001 (2016)
  • Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
    The 30th International Symposium on Rarefied Gas Dynamics 2016年07月 口頭発表（一般） University of Victoria Victoria BC Canada 
    AIP Conf. Proc., 1786, 110002, (2016)
  • Effects of surrounding gas temerature on ethanol droplet impact on solid surface  [通常講演]
    T. Isono, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada
    9th International conference on multiphase flow (ICMF2016) 2016年05月 口頭発表（一般）
  • Observation of non-sperical droplet imacts with velocities of O(10 m/s)  [通常講演]
    Y. Kataoka, Y. Hori, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada
    9th International conference on multiphase flow (ICMF2016) 2016年05月 口頭発表（一般）
  • Numerical analysis of bubble dynamics with vapor-liquid boundary conditions derived from molecular gas dynamics  [通常講演]
    S. Morikawa, J. Jinbo, Y. Tatekura, K. Kobayashi, M. Watanabe, H. Fujii, K. Sasaki
    9th International conference on multiphase flow (ICMF2016) 2016年05月 口頭発表（一般）
  • Numerical simulation of vapor-gas bubble dynamics based on molecular gas dynamics  [通常講演]
    T. Nagayama, M. Kon, K. Kobayashi, M. Watanabe, H. Fujii, H. Takahira
    9th International conference on multiphase flow (ICMF2016) 2016年05月 口頭発表（一般）
  • Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
    30TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS (RGD 30) 2016年 AMER INST PHYSICS
     
    The aim of this study is to construct the kinetic boundary condition for Ar-Ne binary mixture in equilibrium using molecular dynamics (MD) simulations. The temperature of the MD simulation system is 85 K; Ar molecules behave as condensable gas (vapor), and Ne molecules behave as non-condensable gas (gas). In this simulation, we utilize the two-boundary method improved by our previous study to investigate behaviors of Ar and Ne molecules at the interface. From the results, we can obtain the molecular mass fluxes at the interface, and evaluate the values of evaporation and condensation coefficients of Ar (vapor) and Ne (gas) molecules.
  • Misaki Kon, Kobayashi Kobayashi, Masao Watanabe
    2nd European conference on non-equilibrium gas flow 2015年12月 口頭発表（一般） Eindhoven, the Netherlands 
    Proceedings of 2nd European conference on non-equilibrium gas flow, No. 50, 1 page.
  • Y Jinbo, K Kobayashi, M Watanabe, H Takahira
    Journal of Physics: Conference Series 2015年12月 IOP Publishing
     
    The ghost fluid method is improved to include heat and mass transfer across the gas-liquid interface during the bubble collapse in a compressible liquid. This transfer is due to both nonequilibrium phase transition at the interface and diffusion of the noncondensable gas across the interface. In the present method, the ghost fluids are defined with the intention of conserving the total mass, momentum, and energy, as well as the mass of each component while considering the heat and mass fluxes across the interface. The gas phase inside the bubble is a mixture of vapor and noncondensable gas, where binary diffusion between the mixture components is taken into account. The gas diffusion in the surrounding liquid is also considered. This method is applied to a simulation of a single spherical bubble collapse with heat and mass transfer across the interface in a compressible liquid. When noncondensable gas is present, it accumulates near the interface due to vapor condensation, thereby preventing further condensation. This results in a weaker bubble collapse than the case without noncondensable gas.
  • Numerical simulation of bubble collapse and tranfer of vapor and noncondensable gas through the bubble interface using the ghost fluid method  [通常講演]
    Y. Jinbo, K. Kobayashi, M. Watanabe, H. Takahira
    9th International symposium on cavitation (CAV2015) 2015年12月 口頭発表（一般）
  • Study on Pressure Wave Propagation in a Liquid Containing Spherical Bubbles in a Rectangular Duct  [通常講演]
    J. Kawahara, M. Watanabe, K. Kobayashi
    9th International symposium on cavitation (CAV2015) 2015年12月 口頭発表（一般）
  • Numerical study of Light Propagation in Agricultural Products for Non-destructive Assessment of Food Quality  [通常講演]
    K. Hattori, H. Fujii, Y. Tatekura, K. Kobayashi, M. Watanabe
    Biophotonics Japan 2015年10月 口頭発表（一般）
  • Numerical simulation of compressible two-phase flows in high-speed impingement of a hollow droplet on a solid wall  [招待講演]
    Y. Jinbo, K. Kobayashi, M. Watanabe, T. Sanada
    EMN Meeting on Droplets 2015年05月 
    【Invited】Total 1 page
  • Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
    BIOPHOTONICS JAPAN 2015 2015年 SPIE-INT SOC OPTICAL ENGINEERING
     
    An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product; then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis.
  • Molecular dynamics simulation on evaporation molecules in a vapor-liquid equilibrium state  [通常講演]
    Kazumichi Kobayashi, Kazumasa Hori, Hisao Yaguchi, Masao Watanabe
    THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2014年07月 口頭発表（一般） Xi'an, China 
    AIP Conf. Proc. 1628, 404 (2014); http://dx.doi.org/10.1063/1.4902621
  • Numerical analysis of kinetic boundary conditions at net evaporation/condensation interfaces in various liquid temperatures based on mean-field kinetic theory  [通常講演]
    Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
    THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2014年07月 口頭発表（一般） Xi'an, China 
    AIP Conf. Proc. 1628, 398 (2014); http://dx.doi.org/10.1063/1.4902620
  • Acoustic Characteristics of Compressible Bubbly Liquids: Study Based on Equation of Motion of Spherical Bubbles  [通常講演]
    Junya KAWAHARA, Kazumichi KOBAYASHI, Masao WATANABE
    8th International Conference on Multiphase Flow 2013年05月 
    No. 260, Total 5 pages
  • Numerical simulations of impact pressure generated by single-droplet impact  [通常講演]
    Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
    8th International Conference on Multiphase Flow 2013年05月 口頭発表（一般） 
    No. 521, Total 5 pages
  • Numerical analysis of nonequilibrium phase change phenomena between two liquid slabs with different temperature  [通常講演]
    Kon M, Kobayashi K, Watanabe M
    13th UK Heat Transfer conference 2013年 
    No. 41, Total 6 pages, 2013
  • Numerical analysis of vapor-liquid two-phase system based on the Enskog-Vlasov equation  [通常講演]
    Kazumichi Kobayashi, Kotaro Ohashi, Masao Watanabe
    THE 28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2012年07月 口頭発表（一般） 
    AIP Conf. Proc.
  • Nonlinear Resonant Gas Oscillation Accompanied with Evaporation and Condensation  [招待講演]
    Masashi Inaba, Takeru Yano, Kazumichi Kobayashi, Masao Watanabe
    THE 28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2012年07月 口頭発表（招待・特別） 
    【INVITED】AIP Conf. Proc.
  • Resonant Gas Oscillation with Evaporation and Condensation  [通常講演]
    M. Inaba, T. Yano, M. Watanabe, K. Kobayashi
    19th International Symposium on Nonlinear Acoustics 2012年 口頭発表（一般） 
    AIP Conf. Proc., No. 1474, pp.79-82, (2012).
  • Derivation of Nonlinear Wave Equations for Ultrasound Beam in Nonuniform Bubbly Liquids  [通常講演]
    T. Kanagawa, T. Yano, J. Kawahara, K. Kobayashi, M. Watanabe, S. Fujikawa
    19th International Symposium on Nonlinear Acoustics 2012年 口頭発表（一般） 
    AIP Conf. Proc., No. 1474, pp.143-146, (2012).
  • Innovative Ultra-Low Environmental Load Cleaning Method Using Steam-Water Mixed Spray: II. Micro-Scale Approach  [通常講演]
    M. Watanabe, K. Kobayashi, T. Sanada
    6th Japanese-European Two-Phase Flow Group Meeting 2012年 口頭発表（一般） 
    Total 6 pages (CD-ROM), (2012)
  • Innovative Ultra-Low Environmental Load Cleaning Method Using Steam-Water Mixed Spray: I. Macro-Scale Approach  [通常講演]
    T. Sanada, M. Watanabe, K. Kobayashi
    6th Japanese-European Two-Phase Flow Group Meeting 2012年 口頭発表（一般） 
    Total 6 pages (CD-ROM)
  • Droplet Impact as an Elementary Process of Physical Cleaning  [通常講演]
    K. Kobayashi, R. Uemura, M. Watanabe, T. Sanada, A. Hayashida
    9th International Conference on Fluid Dynamics 2012年 口頭発表（一般） 
    Total 2 pages (CD-ROM), (2012).
  • Toshihide Fujikawa, Yuuki Tatekura, Kazumichi Kobayashi, Toshiyuki Sanada, Atsushi Hayashida, Masao Watanabe
    ECS Transactions 2011年10月 The Electrochemical Society
     
    In the steam-water mixed spray-cleaning technique, droplet impact on the solid surface is the one of the primarily important physical processes. We experimentally studied a droplet impact on a solid plate that moves with a speed ranging from 1 to 50 m/s using high-speed video camera. We observed that high-speed liquid film flows radially outward along the surface just after the impact. In addition, we also observed that liquid turns into corona splash in the cases of higher impact velocities. These flows with large velocities can generate huge shear stress on the solid surface, which may contribute to cleaning. Furthermore, we numerically studied the velocity field development and found that gas flow also spreads obliquely upward. The obliquely upward flow field may also contribute in advecting removed particles or stripped resists away from the original place.
  • Ultrasound Beam Radiated From Circular Piston in Bubbly Liquids: Nonlinear Analysis for Envelope of Short Waves With Diffraction Effect  [通常講演]
    J. Kawahara, K. Kanagawa, T. Yano, K. Kobayashi, M. Watanabe, S. Fujikawa
    ASME-JSME-KSME 2011 Joint Fluids Engineering Conference 2011年 
    Paper No. AJK2011-33019, pp. 251-256 (2011).
  • Nonlinear Propagation of Sound Beam in Nonuniform Bubbly Liquids  [通常講演]
    T. Kanagawa, J. Kawahara, T. Yano, K. Kobayashi, M. Watanabe, S. Fujikawa
    ASME-JSME-KSME 2011 Joint Fluids Engineering Conference 2011年 口頭発表（一般） 
    Paper No. AJK2011-33017, pp. 237-241 (2011).
  • High-Speed Droplet Impact as an Elementally Process of Physical Cleaning  [通常講演]
    T. Fujikawa, Y. Tatekura, K. Kobayashi, T. Sanada, A. Hayashida, M. Watanabe
    ECS Meeting 2011年 口頭発表（一般） 
    ECS Transaction, Vol.41, pp. 67-74 (2011).
  • Numerical Analysis of Shock-Bubble Interactions near Tissue Boundaries  [通常講演]
    Kazumichi Kobayashi
    6th Japan-Taiwan Workshop on Mechanical and Aerospace Engineering 2011年 口頭発表（一般） 
    Total 8 pages (CD-ROM), (2011).
  • Direct Numerical Simulations of Bubble Collapse near a Tissue Surface with the Ghost Fluid Method  [通常講演]
    H. Takahira, K. Kobayashi
    157th meeting of Acoustic Society of America 2009年 口頭発表（一般） 
    Journal of Acoustic Society of America, 124, 2712
  • Influence of Shock-Bubble and Bubble-Bubble Interactions on the Collapse of a Cluster of Bubbles  [通常講演]
    K. Kobayashi, Y. Jinbo, H. Takahira
    7th International Symposium of Cavitation (Cav2009) 2009年 口頭発表（一般） 
    Total 11 pages (CD-ROM), No.53, (2009)
  • Numerical Investigations of Interactions between Shock Waves and Bubbles near Tissue Surface Using the Ghost Fluid Method  [通常講演]
    S. Syu, T. Matsuno, K. Kobayashi, H. Takahira
    7th JSME-KSME Thermal and Fluid Engineering Conference 2008年 口頭発表（一般） 
    Total 2 pages (CD-ROM，No.E322), (2008)
  • Molecular Gas Dynamics Simulations for the Collapse of Gas or Vapor Bubbles  [通常講演]
    K. Kobayashi, H. Takahira
    7th JSME-KSME Thermal and Fluid Engineering Conference 2008年 口頭発表（一般） 
    Total 2 pages (CD-ROM, No.E313), (2008).
  • Flow Structure and Bubble Fission of Gas-Liquid Two-Phase Venturi Tube Flows  [通常講演]
    K. Umeyama, K. Ikema, K. Kobayashi, H. Takahira
    7th JSME-KSME Thermal and Fluid Engineering Conference 2008年 口頭発表（一般） 
    Total 2 pages (CD-ROM，No.E122), (2008).
  • Molecular Gas Dynamics Simulation of the Collapse of Condensable Gas bubbles  [通常講演]
    K. Kobayashi, H. Takahira
    Cavitation in Turbo-Machinery & Medical Applications 2008年 口頭発表（一般） 
    pp.204-209(CD-ROM), (2008)
  • Numerical Analysis of Shock-Bubble Interactions near Boundaries Using the Ghost Fluid Method  [通常講演]
    K. Kobayashi, T. Matsuno, S. Syu, H. Takahira
    Cavitation in Turbo-Machinery & Medical Applications 2008年 口頭発表（一般） 
    pp.190-194, (CD-ROM), (2008).
  • Condensation Coefficient of Water in a Weak Condensation State  [通常講演]
    K. Kobayashi, S. Watanabe, D. Yamano, T. Yano, S. Fujikawa
    1st International Colloquium on Dynamics, Physics and Chemistry of Bubble and Gas-Liquid Boundaries 2007年 口頭発表（一般） 
    Total 10 pages (CD-ROM), (2007).
  • Shock-Tube-Deduced Condensation Coefficients of Methanol and Water Vapors  [通常講演]
    S. Watanabe, K. Kobayashi, M. Inaba, T. Yano, S. Fujikawa
    International Symposium on Advanced Fluid/Solid Science and Technology in Experimental Mechanics 2006年 口頭発表（一般） 
    Total 5 pages (CD-ROM, No.A10-4),(2006)
  • Molecular Gas Dynamics Approaches to Interfacial Phenomena Accompanied with Condensation  [通常講演]
    S. Mikami, K. Kobayashi, T. Ota, S. Fujikawa, T. Yano, M. Ichijo
    ECI International Conference on Heat Transfer and Fluid Flow in Microscale 2005年 口頭発表（一般） 
    Total 4 pages (CD-ROM, No.70), (2005)
  • A New Approach for Determination of Condensation Coefficient of Methanol by Combining Molecular Gas Dynamics Study and Shock Tube Experiment  [通常講演]
    K. Kobayashi, S. Fujikawa, T. Yano
    6th World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics 2005年 口頭発表（一般） 
    Total 5 pages (CD-ROM, No.7-b-7), (2005).
  • Numerical Computations of Vapor Condensation in Vapor-Liquid Nonequilibrium State at Shock Tube Endwall  [通常講演]
    K. Kobayashi, T. Yano, S. Fujikawa
    5th International Conference on Multiphase Flow 2004年 口頭発表（一般） 
    Total 9 pages (CD-ROM, No.413), (2004).
  • Numerical Analysis of Condensation Process of a Polyatomic Vapor behind a Reflected Shock Wave Based on the Kinetic Theory of Gases  [通常講演]
    K. Kobayashi, T. Yano, S. Fujikawa
    15th International Symposium on Transport Phenomena 2004年 口頭発表（一般） 
    Total 5 pages (CD-ROM, No.101), (2004).
  • Numerical Study of Condensation of a Polyatomic Vapor by a Shock Wave Based on the Kinetic Theory of Gases  [通常講演]
    T. Yano, K. Kobayashi, S. Fujikawa
    4th ASME/JSME Joint Fluids Engineering Conference 2003年 口頭発表（一般） 
    Total 6 pages (CD-ROM, No. FEDSM2003-45022), (2003).

担当経験のある科目（授業）

  • 流体力学演習大坂府立大学
  • 機械設計演習大坂府立大学
  • ラボラトリーセミナー北海道大学
  • 計測工学北海道大学
  • テクニカルイングリッシュ北海道大学
  • 熱流体力学演習北海道大学
  • 応用数学演習北海道大学
  • 分子流体力学特論北海道大学

所属学協会

  • 日本伝熱学会   日本混相流学会   日本熱物性学会   日本流体力学会   日本物理学会   日本機械学会   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2024年04月 -2028年03月 
    代表者 : 小林 一道, 藤井 宏之, 渡部 正夫
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2024年04月 -2026年03月 
    代表者 : 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2022年04月 -2025年03月 
    代表者 : 戸谷 剛, 小林 一道
  • 科学技術振興機構(JST)：さきがけ
    研究期間 : 2021年10月 -2025年03月 
    代表者 : 小林一道
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之
     
    本研究の目的は，「高Oh液滴の固体面衝突直後に発生するcorona splashとprompt splashの発生条件を明らかにし，二つのsplashの発生メカニズムを説明する理論モデルを構築すること」である．この目的を達成するために，本年度は以下の２項目について研究を行った． １．固体表面に滴衝する高Oh液滴の観察：自由落下するシリコンオイルを用いて衝突実験を行い，高Oh液滴のsplash発生条件を探索した．高粘度液滴衝突ではあるOhを閾値としてsplashとreceding break-upの２種類の不安定性が観察されること, 閾値Oh数以上ではreceding break-upのみが観察されさらにOh数を大きくすると不安定性が観察されないこと，receding break-upはある衝突速度以上では観察されないことを明らかにした． ２．粗い表面に衝突する液滴の観察：低圧力環境下の高速液滴衝突 (50m/s程度) 実現を行い，固体表面粗さの効果を検討するために，減圧チャンバ内での粗い固体表面への高速液滴衝突を観察した．平滑表面および粗い固体表面においてsplashの発生閾値を検討した．低Oh液滴衝突においては，これまで観察されていたcorona splashとprompt splashに加えて衝突直後極短時間にのみ観察されるsplashが存在することが発見され，これまでに提案されたsplash発生閾値モデルは，粗い表面には適用できないことを明らかにした． ３．高速度カラー光干渉計による気液界面計測システムによる観察：固体表面に衝突する液滴の固体面衝突直前に，固体表面と液滴との間に形成される薄空気膜はsplash発生に大きな影響を与える．この薄空気膜厚さの空間分布の時間変化が，固体表面電位と液体の誘電率によって大きく変化することを明らかにした．
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 藤井 宏之, 西村 吾朗, 渡部 正夫, 小林 一道
     
    本研究の目的は、「生体を模擬した高密度なコロイド溶液に対して、輻射（ふくしゃ）の干渉効果を組み込んだ輻射輸送モデル(輸送モデル)を新たに構築した上で、干渉効果が及ぼす光伝播への影響を明らかにすること」である。生体光イメージングや光治療において、生体内の光伝播を定量的に把握することが必要であり、光を輻射と捉えた輸送モデルが活用されている。しかし、従来の輸送モデルには、生体のような高密度な散乱媒体において重要となる干渉効果が考慮されていない。本研究では電磁波の散乱理論より干渉効果を考慮した散乱特性を計算し、輸送モデルに組み込んだ上で光強度の時間分解波形を数値計算する。また、短パルスレーザー光源による光強度計測も実施する。干渉効果が光伝播へ影響を及ぼす時空間スケールについて、散乱係数などで表される無次元数を用いて解析し、理論、数値計算、実験より体系的に明らかにする。この目的を達成するため、本年度は以下の３項目について研究を実施した。 １．光散乱特性を簡潔に記述するモデル式を開発した。モデル式により、単一散乱の寄与と干渉効果の寄与を分離して評価することに初めて成功した。 ２．分担研究者の西村吾朗助教の波長可変の光計測システムを利用して、コロイド溶液（脂質エマルジョン）において、濃度20%まで21条件、720 nmから860 nmまでの6条件で光計測を実施した。光計測データを逆解析することで算出した光学特性値をモデル式より解析し、干渉効果の波長依存性を明らかにした。 ３．分子動力学シミュレーションにより構造特性を計算し、干渉散乱理論に組み込んで散乱特性を計算した。粒子間の引力相互作用が散乱特性に強く影響を及ぼすことを明らかにした。
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 小林 一道
     
    本提案研究は，混合気体に接した気液界面における気体論境界条件を構築し，様々な分野に本研究成果を展開することである．2021年度は主に以下の３つの研究を行った． １．分子計算（分子運動論および分子動力学シミュレーション）を用いて，非平衡気液界面における気体論境界条件の構築を行った．その結果，気体論境界条件に含まれる二つの未知パラメータ（蒸発係数および凝縮係数）を決定した．本結果より，非平衡気液界面における蒸発係数と凝縮係数の値は，平衡状態および非平衡状態においてほぼ変わらないことが明らかとなった．これにより，初期液体温度などの条件にもよるが，平衡状態の蒸発係数および凝縮係数を求めておけば気体論境界条件を構築できることが示唆された． ２．分子動力学解析を用いて，固体壁と液体に挟まれた気体のクエット流れについて解析を行った．この研究より，気液界面における気体論境界条件の位置を検証した．本研究より，１の研究で指定していた気体論境界条件の位置は妥当であることが示唆された．また，高クヌーセン数流れになるほど，気液界面の境界条件が平衡状態の関数形から異なることが示唆された．これについてはさらなる検討が必要である． ３．分子動力学解析を用いて，混合液体（エタノール・イソオクタン）の蒸発について検証した．分子動力学計算を用いてエタノール・イソオクタンの気液平衡系を作り出し，１の研究で提案した方法によって，液体から蒸発する分子の成分について調べた．その結果，エタノールの濃度が低い混合液体においても，蒸発するエタノール分子の割合は高くなることが示された．今後はこの知見を用いて実験結果を整理する予定である．
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 戸谷剛, 小林一道
  • 細い穴の中における気体分子の振る舞い (2)
    企業：共同研究
    研究期間 : 2020年07月
  • 細い穴の中における気体分子の振る舞い (1)
    企業：共同研究
    研究期間 : 2019年12月 -2020年06月
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2018年04月 -2020年03月 
    代表者 : 渡部正夫
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2017年04月 -2020年03月 
    代表者 : 渡部正夫
  • 超音波と微細気泡を用いた混合液体分離技術の開発
    公益信託小野音響学研究助成基金：公益信託小野音響学研究助成基金
    研究期間 : 2019年04月 -2019年12月 
    代表者 : 小林一道
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 小林一道
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 渡部 正夫, 真田 俊之, 小林 一道, 矢口 久雄, 藤井 宏之
     
    固体表面への液滴衝突は噴霧冷却，インクジェット印刷，超清浄洗浄等の技術応用において重要な技術的要素である．本研究では，Xuら（Phys. Rev. Lett, 184505, 2005）の液滴衝突後に発生する高速液膜の不安定現象発生閾圧力についてのモデルが，周囲気体温度の寄与を予測することが可能であることを示した．さらに周囲気体が凝縮性気体の場合には，高速液膜の不安定現象発生閾圧力がXuらのモデルでは予測できず，不安定現象発生閾圧力はより高く，すなわち安定化することを示した．
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 渡部正夫
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 小林一道
  • 集束超音波と液面の相互作用による液体ジェット生成技術の開発
    ノーステック財団研究開発助成事業：若手研究人材育成事業
    研究期間 : 2015年04月 -2016年02月 
    代表者 : 小林一道
  • マイクロヒートポンプ内の相変化を伴う気液二流体流れの基礎研究
    北海道ガス：北海道ガス大学助成制度
    研究期間 : 2013年04月 -2014年03月 
    代表者 : 小林一道
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2011年04月 -2013年03月 
    代表者 : 渡部正夫
     
    液体燃料ロケットエンジンの信頼陸の向上のために,燃料混合気の濃度分布の高精度予測のための,気液混合界面での輸送現象の解明を目的としている.相変化が存在する気液界面における輸送現象を評価するために,平均場運動論理論から得られるEnskog-Vlasov方程式を用いることにより,界面の物理特陸を評価するために数値解析手法を解析し,分子動力学シミュレーション結果と比較することにより,混合界面での熱・物質輸送現象を検討する.
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2010年04月 -2013年03月 
    代表者 : 小林一道
     
    気体－液体界面における素過程を考慮し，分子動力学や気体分子論の立場から流体体力学へ応用可能な境界条件のモデルを導出し流体力学シミュレーションへの応用を目指す．
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2010年04月 -2013年03月 
    代表者 : 渡部 正夫
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2009年04月 -2013年03月 
    代表者 : 高比良 裕之
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2009年04月 -2011年03月 
    代表者 : 藤川 重雄
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2009年04月 -2011年03月 
    代表者 : 渡部 正夫
  • 日本学術振興会：科学研究費補助金
    研究期間 : 2007年04月 -2009年03月 
    代表者 : 小林一道
     
    分子動力学および分子気体力学を用いて気液界面での蒸発・凝縮メカニズムの分子論的解明を行う。また、前述の研究から得られた知見を用いて気液界面で蒸発・凝縮現象を伴う気泡のダイナミクスに関する研究を行う．
  • 日本学術振興会：特別研究員奨励費
    研究期間 : 2006年04月 -2007年03月 
    代表者 : 小林一道
  • Evaporation/Condensation Phenomena, Numerical Simulation of Kinetic Theory of Gases, Molecular Dynamics

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