九州大学 研究者情報
論文一覧
浅井 光輝(あさい みつてる) データ更新日:2023.11.22

准教授 /  工学研究院 社会基盤部門 構造及び地震工学


原著論文
1. Kumpei Tsuji, Mitsuteru Asai, Kiyonobu Kasama, Seepage failure prediction of breakwater using an unresolved ISPH-DEM coupling method enriched with Terzaghi’s critical hydraulic gradient, Advanced Modeling and Simulation in Engineering Sciences, https://doi.org/10.1186/s40323-022-00239-3, 10, 2023.01.
2. Daniel Shigueo Morikawa, Kumpei Tsuji, Mitsuteru Asai, Corrected ALE-ISPH with novel Neumann boundary condition and density-based particle shifting technique, Journal of Computational Physics: X, https://doi.org/10.1016/j.jcpx.2023.100125, 17, 2023.03.
3. 藤岡秀二郎,辻勲平,浅井光輝, 高精度SPH法 ~空間2次精度の勾配・ラプラシアン・混合微分~, Japanese Journal of JSCE, 10.2208/jscejj.22-15019, 79, 15, n/a-n/a, 2023.02.
4. 佐伯勇輔,#辻勲平,浅井光輝, 負圧を含む非圧縮性流体を対象としたSPH法の圧力勾配モデルの原点回帰, Japanese Journal of JSCE, 10.2208/jscejj.22-15023, 79, 15, n/a-n/a, 2023.02.
5. 出口翔大,柴田洋佑,浅井光輝, 空間特徴量抽出を援用したPINNsによるパラメータ逆解析の効率化, Japanese Journal of JSCE, 10.2208/jscejj.22-15011, 79, 15, n/a-n/a, 2023.02.
6. 柴田洋佑,町田禎弥,西村和也,備瀬竜馬,浅井光輝, 転移学習で強化したGANによる稀少データから写実的な都市画像の自動生成, AI・データサイエンス論文集, Vol.3, J2, 551-557, 2022.09.
7. Daniel S. Morikawa, Mitsuteru Asai, A phase-change approach to landslide simulations: Coupling finite strain elastoplastic TLSPH with non-Newtonian IISPH, COMPUTERS AND GEOTECHNICS, 10.1016/j.compgeo.2022.104815, 148, 2022.08, The present work shows a novel phase-change concept for simulating landslides using the smoothed particles hydrodynamics (SPH) method. The idea is to initiate the simulation of a slope stability problem with a Solid Mechanics-based SPH, modeling the soil as an elastoplastic material at finite strain. Next, if a particle exceeds a certain level of plastic strain, such particle changes its phase to a fluid state with non-Newtonian rheology, which is then solved with a Fluid Dynamics-based SPH method. We use the total Lagrangian SPH (TLSPH) method to solve the Solid Mechanics phase to avoid problems related to particle distribution (such as the tensile instability), while the implicit incompressible SPH (IISPH) to solve the Fluid Dynamics part to avoid the restriction on time increment in relation to high values of viscosity. The coupling between the two phases is treated as a conventional fluid-solid interaction (FSI) problem. We verified the proposed TLSPH method with the triaxial compression problem and demonstrated the robustness of the proposed phase-change TLSPH-IISPH coupled method in the simulation of the Aso landslide. Specifically, it may be the first time to simulate the Aso landslide from its initiation to its propagation in a single numerical simulation..
8. Masashi Watanabe, Taro Arikawa, Naoto Kihara, Chiaki Tsurudome, Koichi Hosaka, Tatsuto Kimura, Takayuki Hashimoto, Fumitaka Ishihara, Takemi Shikata, Daniel Shigueo Morikawa, Taiga Makino, Mitsuteru Asai, Yu Chida, Yoichi Ohnishi, Simone Marras, Abhishek Mukherjee, Juan Carlos Cajas, Guillaume Houzeaux, B. D. Paolo, Javier L. Lara, Gabriel Barajas, Inigo J. Losada, Masanobu Hasebe, Yoshinori Shigihara, Tatsuya Asai, Tsuyoshi Ikeya, Shusaku Inoue, Hideo Matsutomi, Yoshiaki Nakano, Yasuo Okuda, Shunya Okuno, Takayuki Ooie, Gaku Shoji, Tomokazu Tateno, Validation of tsunami numerical simulation models for an idealized coastal industrial site, COASTAL ENGINEERING JOURNAL, 10.1080/21664250.2022.2072611, 64, 2, 302-343, 2022.04, Numerous tsunami numerical models have been proposed, but their prediction accuracies have not been directly compared. For quantifying the modeling uncertainties, the authors statistically analyzed the prediction results submitted by participants in the tsunami blind contest held at the 17th World Conference on Earthquake Engineering. The reproducibility of offshore water level generated due to the tsunami with soliton fission significantly decreased when the nonlinear shallow water equation models (NSWE) was used compared to three-dimensional (3D) models. The inundation depth was reproduced well in 3D models. However, the reproducibility of wave forces acting on the structure and velocities over land was lower in 3D models than that in NSWE models. For cases where the impulsive tsunami wave pressure generated could not be calculated based on the hydrostatic assumption, the prediction accuracy of the NSWE models was higher than that of the 3D models. The prediction accuracies of both models were not improved at small grid-cell sizes. The NSWE model cannot simulate the short-wave component and vertical pressure distribution. Therefore, further developments in 3D models and smoothed particle hydrodynamics methods (SPH) are needed. The presented results contribute to the future development of tsunami numerical simulation tools..
9. Daniel S. Morikawa, Mitsuteru Asai, Soil-water strong coupled ISPH based on u-w-p formulation for large deformation problems, Computers and Geotechnics, https://doi.org/10.1016/j.compgeo.2021.104570, 2022.02, 豪雨時の斜面崩壊など、地盤における水と土の連成問題の予測が求められている。粒子法の一つであるISPH法は、これまで主に水のみを対象とした解析技術として発展してきたが、この解析手法の拡張し、水と土の連成現象を強連成の定式化で解析できる手法を構築した。.
10. 辻勲平,浅井光輝,笠間清伸, ISPH-DEMによるマウンド変形・ケーソン滑動を考慮した防波堤浸透崩壊シミュレーション, 土木学会論文集A2(応用力学)特集号, Vol.77, 2, I_105-I_116, 2022.02.
11. 出口翔大,柴田洋佑,浅井光輝, 予測に物理的意味を付与した機械学習PINNsによる誤差を含む教師データからのパラメータ推定, 土木学会論文集A2(応用力学)特集号, Vol.77, 2, I_35-I_45, 2022.02.
12. Daniel S. Morikawa, Mitsuteru Asai, Soil-water strong coupled ISPH based on u - w - p formulation for large deformation problems, COMPUTERS AND GEOTECHNICS, 10.1016/j.compgeo.2021.104570, 142, 2022.02, This paper is dedicated to the introduction of a strong coupled soil-water interaction formulation based on an incompressible smoothed particle hydrodynamics (ISPH) framework. The method is based on the u-w-p Biot's formulation and adapted to a semi-implicit projection method for incompressibility condition of pore water and soil grains. The SPH Lagrangian particles move according to the soil velocity, while water variables are embedded into such soil particles. This allows to solve the pressure Poisson equation in a strong coupling way, in addition to enable to update the Darcy's drag force implicitly. A simple boundary treatment on natural boundary conditions for soil particle is proposed to take into account both non-penetration and friction effects. The proposed method was verified and validated through a series of numerical tests resulting in good agreements with both theoretical and experimental results. Finally, we show the applicability of the proposed method in the famous Selborne experiment, a full-scale slope failure problem..
13. Daniel S. Morikawa, Mitsuteru Asai, Coupling total Lagrangian SPH-EISPH for fluid-structure interaction with large deformed hyperelastic solid bodies, Computer Method in Applied Mechanics and Engineering, https://doi.org/10.1016/j.cma.2021.113832, 2021.08, 粒子法による流体構造連成解析をする際,特に構造解析の大変形解析が不安定になり,ロバストに解析が実施することが困難であった。そこで、超弾性体モデルの範囲内であれば、初期配置と現配置の間に1対1の関係があることを利用し、固体のつり合い問題を初期配置で解くTotalラグランジュ記述によるSPH粒子法を利用した新しい流体構造連成解析法を提案した。.
14. Daniel S. Morikawa, Mitsuteru Asai, Coupling total Lagrangian SPH-EISPH for fluid-structure interaction with large deformed hyperelastic solid bodies, COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING, 10.1016/j.cma.2021.113832, 381, 113832-113832, 2021.08, In this work, we propose a two-way coupling technique between a total Lagrangian smoothed particle hydrodynamics (SPH) method for Solid Mechanics and the explicit incompressible SPH (EISPH) to simulate fluid-structure interaction problems. In the solid part, the total Lagrangian framework guarantees that the particle distribution keep stable to correctly calculate the deformation gradient and thus the elastic forces. The constitutive model follows hyperelastic formulations, and the stability of the method is enforced by a Jameson-Schmidt-Turkel (JST) stabilization procedure. For the fluid part, we applied an EISPH formulation, which is a fully explicit incompressible scheme based on a projection method capable of providing accurate pressure distributions for free-surface flows, while avoiding costly linear equations. The coupling scheme follows the same manner as the fixed wall ghost particle (FWGP) approach, which was here adapted to include moving walls. In addition, the non-penetration condition is rigorously reinforced through a numerical algorithm to avoid penetration of every fluid particle, including free-surface particles. Our method for solid is then verified through a large deformed tension plate numerical test, and our coupling forces through a series floating tests and hydrostatic water column over a thin infinite plate. Then, the method is validated comparing it with experimental data of a dam break test in which the water column attacks a thin rubber plate. (C) 2021 Elsevier B.V. All rights reserved..
15. Daniel Morikawa, Harini Senadheera, Mitsuteru Asai, Explicit incompressible smoothed particle hydrodynamics in a multi-GPU environment for large-scale simulations, COMPUTATIONAL PARTICLE MECHANICS, 10.1007/s40571-020-00347-0, 8, 3, 493-510, 2021.05, © 2020, OWZ. We present an explicit incompressible smoothed particle hydrodynamics formulation with stabilized pressure distribution and its implementation in a multiple graphics processing unit environment. The pressure Poisson equation is stabilized via both pressure invariance and divergence-free conditions, and its explicit formulation is derived using the first step of the Jacobi iterative solver. Also, we show how to adapt the fixed wall ghost particle for the boundary condition into our explicit approach. Verification and validation of the method include hydrostatic and dam break numerical tests. The computational performance in the multi-GPU environment was notably high with reasonable speedup values compared to our single-GPU implementation. In particular, our code allows simulations with very large number of particles reaching up to 200 million per GPU card. Finally, to illustrate the potential of our formulation in simulating natural disasters, we present a simulation of the famous Fukushima Dai-ichi Power Plant inundation by the tsunami from The Great East Japan Earthquake in 2011, in Japan..
16. Mitsuteru Asai, Yi Li, Bodhinanda Chandra, Shinsuke Takase, Fluid–rigid-body interaction simulations and validations using a coupled stabilized ISPH–DEM incorporated with the energy-tracking impulse method for multiple-body contacts, Computer Methods in Applied Mechanics and Engineering, 10.1016/j.cma.2021.113681, 377, 113681-113681, 2021.04, © 2021 The Author(s) In this paper, a new particle-based fluid–rigid-body interaction simulator for violent free-surface flow problems is developed. The incompressible Smoothed Particle Hydrodynamics (ISPH) method has been proven to produce a smooth and accurate pressure distribution of free-surface fluid flow with breaking and fragmentation. Computed hydrodynamic forces can be applied onto rigid bodies, which may simultaneously experience contact or impact with the surrounding wall boundaries or another rigid body. Modeled by using the discrete element method (DEM), the contact force between rigid bodies is traditionally calculated employing the penalty approach, where a spring-based repulsive force is approximated at the vicinity of contact points depending on the deepest penetration depth. However, for high-speed collision problems involving a system of many rigid bodies, the values of approximated repulsive forces may be highly overestimated, and thus, a much smaller time step and an excessive damping parameter are often required to stabilize the approximated forces. This problem is highly inefficient for the computational resources of the fluid–rigid body interaction simulation since the computational cost at each time step is mostly dominated by the incompressible fluid simulation. The capability to increase the time increment following the critical time step of the fluid solver is, therefore, strongly demanded to increase the simulation efficiency. The current paper incorporates the usage of the energy-tracking impulse (ETI) method as an alternative approach to handle contact accurately. To achieve better energy conservation and enhance stability, Stronge's hypothesis is considered instead of the generally assumed Newton's contact law. The current work also covers three experimental validation tests, which were conducted to assure the quality and robustness of the coupled ISPH–DEM implementation..
17. Yi Li, Mitsuteru Asai, Bodhinanda Chandra, Masaharu Isshiki, Energy-tracking impulse method for particle-discretized rigid-body simulations with frictional contact, COMPUTATIONAL PARTICLE MECHANICS, 10.1007/s40571-020-00326-5, 8, 2, 237-258, 2021.03, © 2020, OWZ. Simulations of multi-body dynamics for computer graphics, 3D game engines, or engineering simulations often involve contact and articulated connections to produce plausible results. Multi-body dynamics simulations generally require accurate contact detection and induce high computational costs because of tiny time increments. As higher accuracy and robustness are continually being sought for engineering purposes, we propose an improved multi-body dynamics simulator based on an impulse method, specifically an energy-tracking impulse (ETI) algorithm that has been modified to handle particle-discretized rigid-body simulations. In order to decrease the computational costs of the simulations, in the current work, we assume a fixed moderate time increment, allowing multiple-point contacts within a single time increment. In addition to that, we distinguish the treatment between point-to-point and multiple-point contacts, which include edge-to-surface and surface-to-surface contacts, through an additional sub-cycling iterations. The improved ETI method was verified with analytical solutions of examples with single-body contact, a frictional slip, and a rolling contact. Moreover, the method was also validated with an experimental test of a line of dominoes with multiple-point contacts. Finally, a demonstration simulation with bodies of complicated shape subjected to a large number of constraints is given to show the optimum performance of the formulation..
18. 藤井 孟大, 浅井 光輝, 井元佑介, 物理速度と輸送速度を区別した選択型デュアル流速ISPH法を用いた混相流解析, 土木学会論文集A2(応用力学)特集号, Vol.76, 2, I_247-I_257, 2021.01.
19. 出口翔大, 浅井 光輝, 植木裕人,竹内友紀,川崎浩司, 数値解析のサロゲートモデリングによる確率論的災害リスク評価手法の開発, 土木学会論文集A2(応用力学)特集号, Vol.76, 2, I_561-I_576, 2021.01.
20. 塩入一希, 三目 直登, 浅井 光輝, 時間解像度が可変な力積型個別要素法の開発, 土木学会論文集A2(応用力学)特集号, Vol.76, 2, I_119-I_129, 2021.01.
21. Zehba Raizah, Mitsuteru Asai, Abdelraheem M. Aly, Incompressible smoothed particle hydrodynamics simulations of natural convection flow resulting from embedded Y-fin inside Y-shaped enclosure filled with a nanofluid, INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW, 10.1108/HFF-02-2020-0094, 31, 1, 154-173, 2021.01, © 2020, Emerald Publishing Limited. Purpose: The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin inside Y-shaped enclosure filled with nanofluid. Design/methodology/approach: The dimensionless governing partial differential equations are described in the Lagrangian form and solved by an implicit scheme of the ISPH method. The embedded Y-fin is kept at a high temperature Th with variable heights during the simulations. The lower area of Y-shaped enclosure is squared with width L = 1 m and its side-walls are kept at a low temperature Tc. The upper area of the Y-shaped enclosure is V-shaped with width 0.5 L for each side and its walls are adiabatic. Findings: The performed simulations revealed that the height of the inner heated Y-fin plays an important role in the heat transfer and fluid flow inside the Y-shaped enclosure, where it enhances the heat transfer. Rayleigh number augments the buoyancy force inside the Y-shaped enclosure and, consequently, it has a strong impact on temperature distributions and strength of the fluid flow inside Y-shaped enclosure. Adding more concentration of the nanofluid until 10% has a slight effect on the temperature distributions and it reduces the strength of the fluid flow inside Y-shaped enclosure. In addition, the average Nusselt number is measured along the inner heated Y-fin and it grows as the Rayleigh number increases. The average Nusselt number is decreasing by adding more concentrations of the nanofluid. Originality/value: An improved ISPH method is used to simulate the natural convection flow of Y-fin embedded in the Y-shaped enclosure filled with a nanofluid..
22. 大村浩之,三目直登,浅井光輝,磯部大吾郎, 壁領域の角を考慮したポリゴン壁境界モデルの開発およびそのISPH法への適用, 日本計算工学論文集, 2021, 2021.01.
23. 松本久也,井元佑介,浅井光輝,三目直登, 底面境界適合型MPS法の開発, 日本計算工学論文集, 2021, 2021.01.
24. Abdelraheem M. Aly, Mitsuteru Asai, Ehab Mahmoud Mohamed, Simulation of water-soil-structure interactions using incompressible smoothed particle hydrodynamics, Computers, Materials and Continua, 10.32604/cmc.2020.09227, 65, 1, 205-224, 2020.07, © 2020 Tech Science Press. All rights reserved. In the present work, an incompressible smoothed particle hydrodynamic (SPH) method is introduced to simulate water-soil-structure interactions. In the current calculation, the water is modelled as a Newtonian fluid. The soil is modelled in two different cases. In the first case, the granular material is considered as a fluid where a Bingham type constitutive model is proposed based on Mohr-Coulomb yield-stress criterion, and the viscosity is derived from the cohesion and friction angle. In addition, the fictitious suspension layers between water and soil depending on the concentration of soil are introduced. In the second case, Hooke's law introduces elastic soil. In ISPH, the pressure is evaluated by solving the pressure Poisson equation using a semi-implicit algorithm based on the projection method and an eddy viscosity for water is modelled by a large eddy simulation with the Smagorinsky model. In the proposed ISPH method, the pressure is stabilized to simulate the multiphase flow between soil and water. Numerical experiments for water-soil suspension flow of Louvain erosional dam break with flat soil foundation, is simulated and validated using 3D-ISPH method. Coupling between water-soil interactions with different solid structures are simulated. The results revealed that, the suspension layers with the Bingham model of soil gives more accurate results in the experiment as compared to the case of the Bingham model without suspension layers. In addition, the elastic soil model by the Hooke's law can simulate soil hump accurately as compared to the Bingham model. From the simulations, avoiding erosion behind the structure for preventing the structure break during flood are investigated by using an extended structure or a wedge structure..
25. Li Yi, Mitsuteru Asai, Bodhinanda Chandra, Masaharu Isshiki, Energy-tracking impulse method for particle-discretized rigid-body simulations with frictional contact, Journal of Computational Particle Mechanics, https://doi.org/10.1007/s40571-020-00326-5, 2020.04, 剛体接触解析を行う常套手段としては、バネとダッシュポットで簡易的に表現するペナルティ法が良く採用されるが、時間増分が小さくなる、また人工パラメータの設定方法が曖昧であるなどの、問題点があった。そこで、適切な力(撃力:インパルス)で接触を表現するインパルス法に着目し、特にエネルギー保存性を担保できるEnergy-tracking impulse法をベースとし、これをDEMなどの粒子離散化された剛体の解析へと適用した。.
26. 浅井光輝、原倖平、磯部大吾郎、田中聖三, ASI-Gauss法による骨組み崩壊解析に基づく阿蘇大橋崩壊メカニズムの推定, 構造工学論文集, Vol.66A, 2020.03.
27. 浅井光輝, 原倖平, 磯部大吾郎, 田中聖三, ASI-Gauss 法による骨組み崩壊解析に基づく阿蘇大橋崩壊メカニズムの推定, 構造工学論文集 A(Web), 10.11532/structcivil.66A.59, 66A, 0, 59-69, 2020.03,

Many bridges and infrastrucutures were damaged by the seismic waves in the 2016 Kumamoto Earthquakes, and in this research, we focused on the Aso-bridge which collapsed immediately after the main shock. A huge landslide happened after the earthquakes and Aso-bridge, which was constructed in the same location of the landslide, totally collapsed. There are a couple of reports that four main factors might have contributed to this collapse; (1) seismic wave, (2) ground deformation, (3) landslide material load increase on the bridge, (4) basement ground collapse. In this paper, a numerical analysis of the Aso-Bridge collapse was conducted using the ASI-Gauss code, which is one of the finite element method utilizing beam elements. Then, we have discussed the main factor of the Aso-bridge collapse.

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28. 井元 佑介, 浅井 光輝, #藤井 孟大, 安定化 ISPH 法の理論的解釈 II ‐誤差評価に基づく安定化係数の最適化‐, 土木学会論文集A2(応用力学)特集号, Vol.74, 2, I_187-I_194, 2020.01.
29. 辻 勲平, 浅井 光輝, 小西 康彦, 大峯 秀一, 含水に伴う見かけの粘着力を考慮した SPH-DEM 連成解析による地盤陥没現象の再現, 土木学会論文集A2(応用力学)特集号, Vol.74, 2, I_203-I_213, 2020.01.
30. 藤井 孟大, 浅井 光輝, 牛島 省, 鳥生 大祐, 洗掘解析に向けた鉛直噴流実験による ISPH-DEM 連成手法の妥当性確認, 土木学会論文集A2(応用力学)特集号, Vol.74, 2, I_249-I_258, 2020.01.
31. Zehba Raizah, Mitsuteru Asai, Abdelraheem M. Aly, Incompressible smoothed particle hydrodynamics simulations of natural convection flow resulting from embedded Y-fin inside Y-shaped enclosure filled with a nanofluid, International Journal of Numerical Methods for Heat and Fluid Flow, 10.1108/HFF-02-2020-0094, 2020.01, [URL], Purpose: The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin inside Y-shaped enclosure filled with nanofluid. Design/methodology/approach: The dimensionless governing partial differential equations are described in the Lagrangian form and solved by an implicit scheme of the ISPH method. The embedded Y-fin is kept at a high temperature with variable heights during the simulations. The lower area of Y-shaped enclosure is squared with width L = 1 m and its side-walls are kept at a low temperature . The upper area of the Y-shaped enclosure is V-shaped with width 0.5 L for each side and its walls are adiabatic. Findings: The performed simulations revealed that the height of the inner heated Y-fin plays an important role in the heat transfer and fluid flow inside the Y-shaped enclosure, where it enhances the heat transfer. Rayleigh number augments the buoyancy force inside the Y-shaped enclosure and, consequently, it has a strong impact on temperature distributions and strength of the fluid flow inside Y-shaped enclosure. Adding more concentration of the nanofluid until 10% has a slight effect on the temperature distributions and it reduces the strength of the fluid flow inside Y-shaped enclosure. In addition, the average Nusselt number is measured along the inner heated Y-fin and it grows as the Rayleigh number increases. The average Nusselt number is decreasing by adding more concentrations of the nanofluid. Originality/value: An improved ISPH method is used to simulate the natural convection flow of Y-fin embedded in the Y-shaped enclosure filled with a nanofluid..
32. 辻勲平, 浅井光輝, 小西康彦, 大峯秀一, 含水に伴う見かけの粘着力を考慮した SPH-DEM 連成解析による地盤陥没現象の再現, 土木学会論文集 A2(応用力学)(Web), 10.2208/jscejam.75.2_I_203, 75, 2, I_203-I_213, 2020.01,

昨今,高度成長期から発達してきた下水道管路の不具合に伴う地盤陥没被害が多発している.本研究では,未だ解析例の少ない地盤陥没現象の 3 次元数値解析を実施した.解析手法として,大変形かつ不連続な運動も追随できる粒子法をベースとした流体-地盤混相流解析手法の開発を行い,粉体工学の分野で研究されている液体架橋力を導入することで,含水に伴う見かけの粘着力を考慮し,不飽和地盤に適応できるように改良を施した.本手法を用いた陥没現象の再現解析により,定性的な陥没現象の再現することに成功し,不飽和地盤における見かけの粘着力と粒子形状の評価の必要性について考察を行った.

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33. 井元佑介, 浅井光輝, 藤井孟大, 安定化 ISPH 法の理論的解釈 II -誤差評価に基づく安定化係数の最適化-, 土木学会論文集 A2(応用力学)(Web), 10.2208/jscejam.75.2_I_187, 75, 2, I_187-I_194, 2020.01,

非圧縮性 Navier–Stokes 方程式に対する粒子法の一つである安定化 ISPH 法は,通常の非圧縮性 SPH 法 (ISPH 法) に粒子密度に関する安定化項を圧力 Poisson 方程式に付加した手法である.この安定化項により,粒子の偏在化を防ぐことができ,計算安定,体積保存,精度向上などが数値計算によって確かめられている.この安定化 ISPH 法に対して,我々は先行研究で安定化項が非圧縮性条件と局所密度一定の条件の誤差を重み付きで近似的に最小化するという解釈ができることを理論的に示した.しかしながら,その誤差の重みを表す安定化係数については,いくらかの数値実験によって最適な範囲や傾向が見積もられているものの,それらを理解するための理論は存在しなかった.そこで,本論文では,経験的に知られている安定化係数の範囲や他のパラメータとの関係性を,誤差評価に基づいて安定化係数を最適化する.さらに,その最適化された安定化係数の性質を示すことで経験則で知られていたことを理論的に解釈する.

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34. 藤井孟大, 浅井光輝, 牛島省, 鳥生大祐, 洗掘解析に向けた鉛直噴流実験による ISPH-DEM 連成手法の妥当性確認, 土木学会論文集 A2(応用力学)(Web), 10.2208/jscejam.75.2_I_249, 75, 2, I_249-I_258, 2020.01,

2011 年の東北地方太平洋沖地震後に発生した津波による防波堤の崩壊原因としては,防波堤前後の水位差による水平力,浸透流によるマウンドの支持力低下に伴うパイピング破壊,越流水によるマウンドの洗掘が主因となり,これらが連成することで崩壊に至ったものと考えられている.著者らはこうした複雑な水と土の相互作用に起因する土構造物の破壊を予測するため,SPH 法と個別要素法(DEM)による水‐土連成解析手法を開発してきた.本研究では,特に礫のみを対象とした洗掘現象に対して,解析ツールによる解析精度の妥当性確認を行いながら,乱流状態となる礫表層部分の抗力モデルの改良の必要性について議論し,その修正モデルを提案し,実験との比較検証を通してその有用性を確認した.

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35. Abdelraheem M. Aly, Zehba Raizah, Mitsuteru Asai, Natural convection from heated fin shapes in a nanofluid-filled porous cavity using incompressible smoothed particle hydrodynamics, International Journal of Numerical Methods for Heat and Fluid Flow, 10.1108/HFF-03-2019-0270, 29, 12, 4569-4597, 2019.12, [URL], Purpose: This study aims to focus on the numerical simulation of natural convection from heated novel fin shapes in a cavity filled with nanofluid and saturated with a partial layer of porous medium using improved incompressible smoothed particle hydrodynamics (ISPH) method. Design/methodology/approach: The dimensionless of Lagrangian description for the governing equations were numerically solved using improved ISPH method. The current ISPH method was improved in term of wall boundary treatment by using renormalization kernel function. The effects of different novel heated (Tree, T, H, V, and Z) fin shapes, Rayleigh number Ra, porous height H (0.2-0.6), Darcy parameter and solid volume fraction ϕ(0.0-0.05) on the heat transfer of nanofluid have been investigated. Findings: The results showed that the variation on the heated novel fin shapes gives a suitable choice for enhancement heat transfer inside multi-layer porous cavity. Among all fin shapes, the H-fin shape causes the maximum stream function and Z-fin shape causes the highest value of average Nusselt number. The concentrations of the fluid flows in the nanofluid region depend on the Rayleigh and Darcy parameters. In addition, the penetrations of the fluid flows through porous layers are affected by porous heights and Darcy parameter. Originality/value: Natural convection from novel heated fins in a cavity filled with nanofluid and saturated with a partial layer of porous medium have been investigated numerically using improved ISPH method..
36. Abdelraheem M. Aly, Zehba Raizah, Mitsuteru Asai, Natural convection from heated fin shapes in a nanofluid-filled porous cavity using incompressible smoothed particle hydrodynamics, International Journal of Numerical Methods for Heat and Fluid Flow, 10.1108/HFF-03-2019-0270, 29, 12, 4569-4597, 2019.12, © 2019, Emerald Publishing Limited. Purpose: This study aims to focus on the numerical simulation of natural convection from heated novel fin shapes in a cavity filled with nanofluid and saturated with a partial layer of porous medium using improved incompressible smoothed particle hydrodynamics (ISPH) method. Design/methodology/approach: The dimensionless of Lagrangian description for the governing equations were numerically solved using improved ISPH method. The current ISPH method was improved in term of wall boundary treatment by using renormalization kernel function. The effects of different novel heated (Tree, T, H, V, and Z) fin shapes, Rayleigh number Ra(103 – 106), porous height Hp (0.2-0.6), Darcy parameter Da(10−5 − 10−1) and solid volume fraction ϕ(0.0-0.05) on the heat transfer of nanofluid have been investigated. Findings: The results showed that the variation on the heated novel fin shapes gives a suitable choice for enhancement heat transfer inside multi-layer porous cavity. Among all fin shapes, the H-fin shape causes the maximum stream function and Z-fin shape causes the highest value of average Nusselt number. The concentrations of the fluid flows in the nanofluid region depend on the Rayleigh and Darcy parameters. In addition, the penetrations of the fluid flows through porous layers are affected by porous heights and Darcy parameter. Originality/value: Natural convection from novel heated fins in a cavity filled with nanofluid and saturated with a partial layer of porous medium have been investigated numerically using improved ISPH method..
37. Daniel Morikawa, Mitsuteru Asai, NurAin Idris, Yusuke Imoto, Masaharu Isshiki, Improvements in highly viscous fluid simulation using a fully implicit SPH method, COMPUTATIONAL PARTICLE MECHANICS, 10.1007/s40571-019-00231-6, 6, 4, 529-544, 2019.10, © 2019, OWZ. This study describes the application of two main improvements in highly viscous fluid simulations using the smoothed particle hydrodynamics (SPH) method: an implicit time integration scheme to overcome the problem of impractically small time step restriction and the introduction of air ghost particles to fix problems regarding the free surface treatment. This study adopts the incompressible SPH as a basis for the implementation of these improvements, which guarantees a stable and accurate pressure distribution. We verified the proposed implicit time integration scheme with simulations of pipe flow and the free surface treatment with a simple hydrostatic problem. As a result, the free surface of the hydrostatic problem became very smooth and stable. In addition, we conducted a variety of dam-break simulations to validate this proposed SPH method, as well as to analyze the density and divergence error. Finally, we demonstrate the potential of this method with the highly viscous vertical jet flow over a horizontal plate test, which features a complex viscous coiling behavior..
38. Masao Ogino, Takuya Iwama, Mitsuteru Asai, Development of a Partitioned Coupling Analysis System for Fluid-Structure Interactions Using an In-House ISPH Code and the Adventure System, INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS, 10.1142/S0219876218430090, 16, 4, 2019.06, © 2019 World Scientific Publishing Company. In this paper, a partitioned coupling analysis system is developed for a numerical simulation of 3-dimensional fluid-structure interaction (FSI) problems, adopting an incompressible smoothed particle hydrodynamics (SPH) method for fluid dynamics involving free surface flow and the finite element method (FEM) for structural dynamics. A coupling analysis of a particle-based method and a grid-based method has been investigated. However, most of these are developed as a function-specific application software, and therefore lack versatility. Hence, to save cost in software development and maintenance, the open source software is utilized. Especially, a general-purpose finite element analysis system, named ADVENTURE, and a general-purpose coupling analysis platform, named REVOCAP-Coupler, are employed. Moreover, techniques of an interface marker on fluid-structure boundaries and a dummy mesh for fluid analysis domain are adopted to solve the problem that the REVOCAP-Coupler performs to unify two or more grid-based method codes. To verify a developed system, the dam break problem with an elastic obstacle is demonstrated, and the result is compared with the results calculated by the other methods..
39. Daniel Morikawa, Mitsuteru Asai, Yusuke Imoto, Masaharu Isshiki, Bingham flow model by fully implicit SPH and its application to reinforce underground caves, Proceedings of the 2019 Rock Dynamics Summit (RDS 2019), 10.1201/9780429327933-48, 2019, 299-304, 2019.05.
40. Daniel Morikawa, Mitsuteru ASAI, Nur' Ain Idris, Yusuke Imoto, Masaharu Isshiki, Improvement in highly viscous fluid simulation using a fully implicit SPH method, Journal of Computational Particle Mechanics, 10.1007/s40571-019-00231-6, 2019.03, 土石流あるいは火砕流などの災害シミュレーションへ向けた高粘性流体のシミュレーションのために、独自に開発してきた粒子法(ISPH法)を改良し、
安定かつ高精度に解析可能な手法を開発した。.
41. Daniel Morikawa, Mitsuteru Asai, Nur’Ain Idris, Yusuke Imoto, Masaharu Isshiki, Improvements in highly viscous fluid simulation using a fully implicit SPH method, Computational Particle Mechanics, 10.1007/s40571-019-00231-6, 6, 4, 1-16, 2019.03, This study describes the application of two main improvements in highly viscous fluid simulations using the smoothed particle hydrodynamics (SPH) method: an implicit time integration scheme to overcome the problem of impractically small time step restriction and the introduction of air ghost particles to fix problems regarding the free surface treatment..
42. 井元佑介、浅井光輝, 安定化ISPH法の理論的解釈 -エネルギー最小化問題からの安定化項の導出-, 土木学会論文集A2(応用力学)特集号, Vol.74, 2, I_159-I_166, 2019.01.
43. 井元佑介, 浅井光輝, 安定化ISPH法の理論的解釈‐エネルギー最小化問題からの安定化項の導出‐, 土木学会論文集 A2(応用力学)(Web), 10.2208/jscejam.74.I_159, 74, 2, I_159‐I_166(J‐STAGE), 2019.01.
44. Abdelraheem M. Aly, Mitsuteru Asai, Water entry of decelerating spheres simulations using improved ISPH method, Journal of Hydrodynamics, 10.1007/s42241-018-0133-3, 30, 6, 1120-1133, 2018.12, © 2018, China Ship Scientific Research Center. In this paper, we simulated the vertical impact of spheres on a water surface using three-dimensional incompressible smoothed particle hydrodynamics (3-D ISPH) method. The sphere motion is taken to be a rigid body motion and it is modeled by ISPH method. The governing equations are discretized and solved numerically using ISPH method. A stabilized incompressible SPH method by relaxing the density invariance condition is adopted. Here, we computed the motions of a rigid body by direct integration of the fluid pressure at the position of each particle on the body surface. The equations of translational and rotational motions were integrated in time domain to update the position of the rigid body at each time step. In this study, we improved the boundary treatment between fluid and fixed solid boundary by using virtual marker technique. In addition, an improved algorithm based on the virtual marker technique for the boundary particles is proposed to treat the moving boundary of the rigid body motion. The force exerted on the moving rigid boundary particles by the surrounding particles, is calculated by the SPH approximation at the virtual marker points. The applicability and efficiency of the current ISPH method are tested by comparison with reference experimental results..
45. Masao OGINO, Takyuya IWAMA, Mitsuteru ASAI, Development of an ISPH-FEM Weak Coupling Analysis System for 3-dimensional Fluid-Structure Interaction Problems, Teroretical and Applied Mechanics Japan, 2018, 2018.08.
46. Masaharu Isshiki, Mitsuteru Asai, Shimon Eguchi, Yoshiya Miyagawa, An Offline-Based On-Demand Visualization System of Large-Scale Particle Simulation for Tsunami Disaster Prevention, ELECTRONICS AND COMMUNICATIONS IN JAPAN, 10.1002/ecj.12050, 101, 4, 55-62, 2018.04, © 2018 Wiley Periodicals, Inc. After the Great East Japan Earthquake Tsunami, new Tsunami disaster-prevention and mitigation methods for the next millennium Tsunami are actively being discussed. Consequently, the methods have highlighted the importance of both hard disaster-prevention method, which means direct prevention using infrastructure such as breakwater, and soft disaster-prevention method, including disaster-prevention education. In this paper, a visualization and polygonization system that can be effectively utilized for Tsunami disaster prevention is proposed for large-scale particle simulation. The system includes two important features, such as engineering-purposed visualization and polygonization for hard and soft tsunami disaster-prevention methods, respectively. Moreover, the system can handle the large-scale particle simulation data that are computed by a high-performance computer via an offline on-demand tool without data transfer..
47. 仲矢直樹、浅井光輝、馬場俊孝、正垣翔大, 2次元差分法による津波遡上解析における建築物・堤防のモデル化忠実度が与える差異, 土木学会論文集A1特集号(地震工学論文集), Vol.74, 4, 2018.03.
48. Masao OGINO, Takyuya IWAMA, Mitsuteru ASAI, Development of a partitioned coupling analyssis system for fluid-structure interactions using an in-house ISPH code and the ADVENTURE system, International Journal of Computational Methods, 2018, 2018.03.
49. 仲矢直樹, 浅井光輝, 馬場俊孝, 正垣翔大, 2次元差分法による津波遡上解析における建築物・堤防のモデル化忠実度が与える差異, 土木学会論文集 A1(構造・地震工学)(Web), 10.2208/jscejseee.74.I_1052, 74, 4, I_1052‐I_1061(J‐STAGE), 2018.03.
50. Li Yi, Mitsuteru ASAI, Fluid-rigid body interaction simulation based on a stabilized ISPH method incorporated with the impulse-based rigid body dynamics, 日本計算工学論文集, https://doi.org/10.11421/jsces.2018.20182010, 2018, 2, p.20182010, 2018.02.
51. LI Yi, 浅井光輝, 安定化ISPH法と撃力法による流体剛体連成解析, 日本計算工学会論文集(Web), 10.11421/jsces.2018.20182010, 2018, 2, 2018.02.
52. 原崎健輔, 浅井光輝, SPH-DEM による固液混相流解析の妥当性確認と粗視化粒子モデルによる洗掘現象解析, 日本計算工学会論文集(Web), 10.11421/jsces.2018.20182001, 2018, 2, 2018.02.
53. 原崎健輔, 浅井光輝, SPH-DEMによる固液混相流解析の妥当性確認と粗視化粒子モデルによる洗掘現象解析, 日本計算工学論文集, https://doi.org/10.11421/jsces.2018.20182010, 2018, 2, p.20182001, 2018.01.
54. 原崎健輔, 浅井光輝, SPH-DEMカップリング解析による防波堤マウンドのパイピング破壊解析, 土木学会論文集A2(応用力学)特集号, Vol.73, 2, I_295-I_304, 2018.01.
55. 小笠原圭太、浅井光輝、古市幹人、西浦泰介, 大規模津波遡上解析に向けた安定化ISPH法の陽的時間積分スキーム, 土木学会論文集A2(応用力学)特集号, Vol.73, 2, I_397-I_404, 2018.01.
56. 一色正晴, 浅井光輝, 江口史門, 宮川欣也, 津波防災に向けた大規模粒子解析のオフライン・オンデマンド可視化システム, 電気学会論文誌 C, 10.1541/ieejeiss.137.1422, 137, 10, 1422-1428, 2018.01.
57. Masao Ogino, Takuya Iwama, Mitsuteru Asai, Development of an ISPH-FENI Weak Coupling Analysis System for 3-Dimensional Fluid -Structure Interaction Problems, THEORETICAL AND APPLIED MECHANICS JAPAN, 10.11345/nctam.64.143, 64, 143-153, 2018.01, This paper focuses on a weak coupling analysis system of 3-dimensional fluid structure interaction problems. As the numerical discretization scheme, the stabilized incompressible smoothed particle hydrodynamics (ISPH) method is adopted for fluid dynamics involving free surface flow and the finite element method (FEM) is used for structural dynamics. To save cost in software developments maintenance, the open source software is utilized. Especially, a general-purpose finite element analysis system, named ADVENTURE Solid, and a general-purpose coupling analysis platform, named REVOCAP Coupler, are employed. Moreover, techniques of an interface marker on the fluid-structure boundary and a dummy mesh for a fluid analysis domain is adopted to solve the problem that the REVOCAP Coupler performs to unify two or more grid-based method codes. To verify a developed system, the dam break problem with an elastic obstacle is demonstrated. Moreover, the effect of a relaxation parameter in the ISPH method is studied..
58. Abdelraheem M. Aly, Mitsuteru Asai, Water Entry of Decelerationg Spheres Simulaitons using Improved ISPH method, Journal of Hydrodynamivs, 2017.03.
59. 瀬戸山雄, 浅井光輝, 原崎健輔, 川崎巧, 福田英二, 3次元離散型有限要素モデルによる石造アーチ橋の静的・動的強度解析, 構造工学論文集 A(CD-ROM), 63, ROMBUNNO.1‐4-48, 2017.03.
60. Keita Ogasawara, Mitsuteru Asai, Mikito Furuichi, Daisuke Nishiura, PERFORMANCE OF LARGE SCALED TSUNAMI RUN-UP ANALYSIS USING EXPLICIT ISPH METHOD, V INTERNATIONAL CONFERENCE ON PARTICLE-BASED METHODS - FUNDAMENTALS AND APPLICATIONS (PARTICLES 2017), 162-171, 2017.01, The tsunami run-up simulation by the particle method at city level needs to huge number of particle at least 1 billion particles. The conventional particle simulation method is not easy to solve these huge problem even on the premise of using super-computer. Then, a new particle method 'fully explicit Incompressible SPH' is developed that takes into consideration both calculation efficiency and accuracy. Finally, we demonstrate the future plan how to use our simulation resultes for a practical 'Soft' disaster mitigation method through the evacuation education with the Virtual Reality(VR) system..
61. Kensuke Harasaki, Mitsuteru Asai, DEVELOPMENT OF A FLUID-SOLID MULTIPHASE FLOW SIMULATOR BY A SPH-DEM COUPLED METHOD FOR SIMULATING A SEAWALL DESTRUCTION DUE TO SOIL FOUNDATION SCOUR, V INTERNATIONAL CONFERENCE ON PARTICLE-BASED METHODS - FUNDAMENTALS AND APPLICATIONS (PARTICLES 2017), 135-145, 2017.01, In 2011, Tohoku-Kanto earthquake tsunami caused serious damage to the port and coastal structures such as breakwaters and seawalls. The damage mechanism of these structures has been studied in the past, and it is found that there are some causes. In this study, a new simulation tool taking account of the soil scouring and seepage flow phenomena is developed to represent and predict the collapse of the breakwater with SPH-DEM coupled method..
62. Masaharu Isshiki, Mitsuteru Asai, Shimon Eguchi, Hideyuki O-Tani, 3D Tsunami Run-up Simulation and Visualization using Particle Method with Gis-Based Geography Model, JOURNAL OF EARTHQUAKE AND TSUNAMI, 10.1142/S1793431116400200, 10, 5, 2016.12, The 2011 off the Pacific coast of Tohoku Earthquake was one of the most powerful earthquakes on record in Japan and the huge tsunami caused by the earthquake inflicted extensive damage to the coastal areas of the Tohoku region. To form safe coastal areas, countermeasures against disaster should be developed considering not only tangible infrastructures including breakwater and bridges but also intangible measures including education on disaster prevention and the development of hazard maps. The tsunami run-up analysis is expected to play a role as one of the countermeasures against tsunami. In this research, we aim to establish a tool to effectively analyze the tsunami run-up in urban areas based on the Smoothed particle hydrodynamics (SPH) method. And then, we propose a series of pre-process procedures to develop a detailed geography analysis model that reflects the geography, elevation, and exterior shapes of buildings by referring to 3D location information and digital elevation model data obtained from a geographical information system. Finally, we established a photorealistic visualization method so that citizen can understand the tsunami phenomenon intuitively..
63. Mitsuteru Asai, Yoshiya Miyagawa, Nur'ain Idris, Abdul Muhari, Fumihiko Imamura, Coupled Tsunami Simulations Based on a 2D Shallow-Water Equation-Based Finite Difference Method and 3D Incompressible Smoothed Particle Hydrodynamics, JOURNAL OF EARTHQUAKE AND TSUNAMI, 10.1142/S1793431116400194, 10, 5, 2016.12, In 2011, the tsunami generated by the Great East Japan Earthquake devastated infrastructure along the Pacific coast of northeastern Japan. In particular, the collapse of bridges resulted in much disruption to traffic, which led to delays in recovery after the disaster. We are developing a multi-scale and multi-physics tsunami disaster simulation tool to evaluate the safety and damage of infrastructure from huge tsunami. Multistage zooming tsunami analysis is one of the possible methods for implementing a high-resolution three-dimensional (3D) tsunami inundation simulation for a city. In this research, a virtual wave source that includes transition layers is proposed for a coupled simulation based on 3D particle simulation. The zooming analysis has been undertaken using the same particle method and a two-dimensional (2D) finite difference simulation. The 3D particle coupled simulation has been examined and validated..
64. Abdelraheem M. Aly, Mitsuteru Asai, ISPH method for double-diffusive natural convection under cross difussion effects in an anisotropic porous cavity/annulus, International Journal of Numerical Methods for Heat & Fluid Flow, 26, 1, 235-268, 2016.10.
65. 宮川欣也, 浅井 光輝, Abdul Muhari, 今村文彦, 仮想造波板による平面2次元解析と3次元粒子法の連成型津波遡上解析, 土木学会論文集A2(地震工学)特集号, 2016.06.
66. 江口史門, 浅井 光輝, 大谷英之, 一色正晴, 建物群を含む地表面詳細モデルを用いた粒子法による三次元津波遡上解析, 土木学会論文集A2(地震工学)特集号, 2016.06.
67. Masaharu Isshiki, Mitsuteru Asai, Shimon Eguchi, Hideyuki O-tani, 3D tsunami run-up simulation and visualization using particle method with GIS-based geography model, Journal of Earthquake & Tsunami, 2016.06.
68. Mitsuteru Asai, Yoshiya Miyagawa, Nur'Ain Idris, Abdul Muhari, Fumihiko Imamura, Coupled tsunami simulation based on a 2D shallow-water equation-based finite difference method and 3D incompressible smoothed particle hydrodynamics, Journal of Earthquake & Tsunami, 2016.06.
69. Yoshiya Miyagawa, Mitsuteru Asai, Multi-Scale Bridge Wash Out Simulation During Tsunami by Using a Particle Method, 3RD INTERNATIONAL CONFERENCE ON CIVIL AND ENVIRONMENTAL ENGINEERING FOR SUSTAINABILITY (ICONCEES 2015), 10.1051/matecconf/20164702019, 47, 2016.04, © Owned by the authors, published by EDP Sciences, 2016. In 2011, the huge tsunami caused by the great east Japan earthquake devastated many infrastructures in pacific coast of north eastern Japan. Particularly, collapse of bridges caused a traffic disorder and these collapse behaviors led to delay of recovery after the disaster. In this study, the bridge wash away accident is selected as a target issue, and it is represented by a numerical simulation. For this purpose, Smoothed Particle Hydrodynamics (SPH) Method, which is one of the pure mesh free methods, is utilized for the rigid body motion simulation. In this study, rigid body motion is introduced for the fluid-rigid interaction behavior during bridge wash away simulation. In the numerical analysis, the upper bridge structure is washed away by receiving an impact fluid force. The wash away simulation of two types of the bridge girder showed good agreement with the real accident on the great east Japan earthquake tsunami..
70. 野上智隆, 浅井 光輝, 有川太郎, Abdelraheem M. Aly, 安定化ISPH法による離脱活動過程を有する洗掘現象の基礎検討, 土木学会論文集A2(応用力学)特集号, 71, 2, 2016.01.
71. 宮川欣也, 浅井 光輝, 粒子法による多段階ズーミング津波解析に向けたマトリックスアレイ状仮想造波板, 土木学会論文集A2(応用力学)特集号, 71, 2, 2016.01.
72. Tomotaka Nogami, Mitsuteru Asai, Kiyonobu Kasama, Taro Arikawa, A Coupling Simulation Between Soil Scour and Seepage Flow by Using a Stabilized ISPH Method, 3RD INTERNATIONAL CONFERENCE ON CIVIL AND ENVIRONMENTAL ENGINEERING FOR SUSTAINABILITY (ICONCEES 2015), 10.1051/matecconf/20164703019, 47, 2016.01, In 2011, the example that breakwaters collapsed because of the basic ground's destabilization was reported by Tohoku-Kanto earthquake tsunami. Fluid-Structure-Soil coupling simulation is desired for a systematic comprehension of the breakwater collapse mechanism, and it may help to develop next disaster prevention method. In this study, A particle simulation tool based on the SPH has been modified and improved to analyze seepage flow and soil scouring. In seepage flow analysis, as a first step, this simulation treat the surface flow and seepage flow interactions by using governing equation. In the scouring analysis, soil scour is judged by an empirical criteria based on quicksand quantity formula..
73. Abdelraheem M. Aly, Mitsuteru Asai, Ali J. Chamkha, Analysis of unsteady mixed convection in lid-driven cavity included circular cylinders motion using an incompressible smoothed particle hydrodynamics method, International Journal of Numerical Methods for Heat and Fluid Flow, 10.1108/HFF-10-2014-0305, 25, 8, 2000-2021, 2015.11, © Emerald Group Publishing Limited. Purpose - The purpose of this paper is to model mixed convection in a square cavity included circular cylinders motion using an incompressible smoothed particle hydrodynamics (ISPH) technique. Design/methodology/approach - The problem is solved numerically by using the ISPH method. Findings - The SPH tool shows robust performance to simulate the rigid body motion in the mixed convective flow with heat transfer, and it may apply easily to complicated problems in 2D and 3D problem without difficulties. Originality/value - The application of the SPH method to mixed convective flow with heat transfer and its potential application easily to complicated 3D problems is original..
74. Abdelraheem M. Aly, Mitsuteru Asai, Three-Dimensional Incompressible Smoothed Particle Hydrodynamics for Simulating Fluid Flows Through Porous Structures, Transport in Porous Media, 10.1007/s11242-015-0568-8, 110, 3, 483-502, 2015.09, © 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results..
75. Abdelraheem M. Aly, Mitsuteru Asai, Three-Dimensional Incompressible Smoothed Particle Hydrodynamics for Simulating Fluid Flows Through Porous Structures, Transport in Porous Media, 10.1007/s11242-015-0568-8, 110, 3, 483-502, 2015.09, © 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results..
76. Abdelraheem M. Aly, Mitsuteru Asai, Three-Dimensional Incompressible Smoothed Particle Hydrodynamics for Simulating Fluid Flows Through Porous Structures, Transport in Porous Media, 10.1007/s11242-015-0568-8, 110, 3, 483-502, 2015.09, © 2015, Springer Science+Business Media Dordrecht. In this paper, a stabilized incompressible smoothed particle hydrodynamics (ISPH) method is presented in three dimensions for simulating fluid flows through porous structures. In the ISPH algorithm, a semi-implicit velocity correction procedure is utilized and the pressure is implicitly evaluated by solving pressure Poisson equation. Evaluated pressure has been improved by relaxing the density invariance condition to formulate a modified pressure Poisson equation. The effect of eddy viscosity by using a sub-particle scale turbulence model is introduced to the entire computational domain. The key point for the application to the non-Darcy flows is to include porosity and drag forces of the medium into ISPH method. Modified density of particles according to their porosity is introduced to satisfy continuity criteria in ISPH method. Tracking free surface with Dirichlet boundary condition is modified for the free surface flows in the porous structure. In this study, different numerical tests for fluid flows through porous structures have been simulated. Also, the results from this investigation are well validated and have favorable comparisons with the experimental results..
77. Abdelraheem M. Aly, Mitsuteru Asai, Modelling of non-Darcy flows through porous media using extended incompressible smoothed particle hydrodynamics, Numerical Heat Transfer, Part B: Fundamentals, 10.1080/10407790.2014.955772, 67, 3, 255-279, 2015.03, Copyright © 2015 Taylor & Francis Group, LLC. In this article, a novel numerical method is presented for the simulation of non-Darcy flows through porous media by the incompressible smooth particle hydrodynamics (ISPH) method with a predictor-corrector scheme. In the ISPH algorithm, a semi-implicit velocity-correction procedure is used and the pressure is obtained by solving the pressure Poisson equation. The key point for the application to non-Darcy flows is to include porosity and drag forces of the medium (the Darcy term and the Forcheimer term) in the ISPH method. Unsteady lid-driven flow, natural convection in non-Darcy porous cavities, and natural convection at a porous medium-fluid interface are examined separately by our extended ISPH method. The results are presented with flow configurations, isotherms, and average Nusselt numbers for different Darcy numbers from 10-4 to 10-2, porosity values from 0.4 to 0.9, and Reynolds/Rayleigh numbers. The flow pattern and rate of heat transfer inside the cavity are affected by these parameters. The results demonstrate the important effect of the Darcy number on both the heat transfer rate and the flow regime. The results from this investigation are well validated and compare favorably with previously published results..
78. 森本敏弘, 浅井 光輝, 笠間 清伸, 藤澤和謙, 井元佑介, 安定化ISPH法による拡張ダルシー則とナビエ・ストークス方程式の統一解法, 土木学会論文集A2(応用力学)特集号, 70, 2, I_213-I_221, 2015.01.
79. 田邊将一, 浅井 光輝, 宮川欣也, 一色正晴, SPH法による流体剛性連成解析とその橋梁流失被害予測への応用, 土木学会論文集A2(応用力学)特集号, 70, 2, I_317-I_328, 2015.01.
80. 浅井 光輝, 合田哲郎, 小國健二, 磯部大吾郎, 樫山和男, 一色正晴, 安定化ISPH法を用いた津波避難ビルに作用する流体力評価, 土木学会論文集A2(応用力学)特集号, 70, 2, I_649-I_658, 2015.01.
81. Abdelraheem M. Aly, Mitsuteru Asai, A. Chamkha, Analysis of Unsteady Mixed Convection in Lid-Driven Cavity Included Circular Cylinders Motion Using an Incompressible Smoothed Particle Hydrodynamics Method, International Journal of Numerical Mechods for Heat and Fluid Flow, 25, 2014.12.
82. 森本敏弘, 浅井 光輝, 水田洋司, 山尾敏孝, ゴムマットを有するコンクリートブロック多段積み構造における共振メカニズムの解析的考察, 構造工学論文集, 60A, 26-34, 2014.03.
83. 田邊将一, 浅井 光輝, 中尾尚史, 伊津野和行, 3次元粒子法による橋桁に作用する津波外力評価とその精度検証, 構造工学論文集, 60A, 293-302, 2014.03.
84. 田邊将一, 浅井光輝, 中尾尚史, 伊津野和行, 3次元粒子法による橋桁に作用する津波外力評価とその精度検証, 構造工学論文集 A(CD-ROM), 10.11532/structcivil.60A.293, 60, ROMBUNNO.6-3-302, 2014.03, On March 11, 2011, the huge tsunami caused by the great east Japan earthquake devastated the Pacific coast of north-eastern Japan. Many infrastructures including bridges were collapsed by the tsunami. New generation of tsunami disaster prevention and mitigation method should be reconsidered toward the next millennium Tsunami. In this study, a new boundary treatment using a virtual marker and the fixed boundary particle is developed to control the slip and no-slip boundary condition for the velocity field and to satisfy the pressure Neumann condition at the same time. Finally, the accuracy and efficiencies of our proposed method are validated by comparison between a numerical solution and experimental results..
85. Abdelraheem M. Aly, Mitsuteru Asai, Incompressible smoothed particle hydrodynamics simulations of fluid-structure interaction on free surface flows, International Journal of Fluid Mechanics Research, 10.1615/InterJFluidMechRes.v41.i6.10, 41, 6, 471-484, 2014.01, [URL], In this paper, fluid-structure interaction (FSI) on free surface flows has been simulated using ISPH method. The governing equations are discretized and solved with respect to Lagrangian moving particles filled within the mesh-free computational domain and the pressure was evaluated by solving pressure Poisson equation using a semi-implicit algorithm based on the projection scheme to ensure divergence free velocity field and density invariance conditions. In this study, the structure is taken as a rigid body and it modeled using ISPH method by two different techniques. In the first technique, the solid particles are treated initially as fluid particles and after corrector step in projection method, the solid constraint is applied to get the rigid body motion. In the second technique, we computed the motions of a rigid body by direct integration of fluid pressure at the position of each particle on the body surface. Then, the equations of translational and rotational motions were integrated in time to update the position of the rigid body at each time step. The applicability and efficiency of current ISPH method with the two different treatment of rigid body are tested by comparison with reference experimental results..
86. Abdelraheem M. Aly, Mitsuteru Asai, Yoshimi Sonda, Modelling of surface tension force for free surface flows in ISPH method, International Journal of Numerical Methods for Heat and Fluid Flow, 10.1108/09615531311301263, 23, 3, 479-498, 2013.12, [URL], Purpose - The purpose of this paper is to show how a surface tension model and an eddy viscosity based on the Smagorinsky sub-grid scale model, which belongs to the Large-Eddy Simulation (LES) theory for turbulent flow, have been introduced into ISPH (Incompressible smoothed particle hydrodynamics) method. In addition, a small modification in the source term of pressure Poisson equation has been introduced as a stabilizer for robust simulations. This stabilization generates a smoothed pressure distribution and keeps the total volume of fluid, and it is analogous to the recent modification in MPS. Design/methodology/ approach - The surface tension force in free surface flow is evaluated without a direct modeling of surrounding air for decreasing computational costs. The proposed model was validated by calculating the surface tension force in the free surface interface for a cubic-droplet under null-gravity and the milk crown problem with different resolution models. Finally, effects of the eddy viscosity have been discussed with a fluid-fluid interaction simulation. Findings - From the numerical tests, the surface tension model can handle free surface tension problems including high curvature without special treatments. The eddy viscosity has clear effects in adjusting the splashes and reduces the deformation of free surface in the interaction. Finally, the proposed stabilization appeared in the source term of pressure Poisson equation has an important role in the simulation to keep the total volume of fluid. Originality/value - An incompressible smoothed particle hydrodynamics is developed to simulate milk crown problem using a surface tension model and the eddy viscosity..
87. Abdelraheem M. Aly, Mitsuteru Asai, YOSHIMI SONODA, Modelling of surface tension force for free surface flows in ISPH method, International Journal of Numerical Methods for Heat and Fluid Flow, 23, 3, 479-498, 2013.04.
88. 藤本啓介, 浅井 光輝, 一色正晴, 舘澤寛, 三上勉, 高解像度地形モデルを用いたISPH法による津波シミュレーション, 地震工学講演会論文集(土木学会論文集A1特集号), A1S-0224
, 2013.04.
89. 渡邊茜, 浅井 光輝, 損傷モデルの概念を導入したボクセルFEMによる物質拡散とひび割れ進展問題の連成解析, 計算工学論文集, No.20130007, 2013.04.
90. 浅井 光輝, 藤本啓介, 田邊将一, 別府万寿博, 階段状の非適合境界を有する粒子法解析における仮想マーカーを用いたすべり・非すべり境界面処理法, 計算工学論文集, No.20130011, 2013.04.
91. Akane Watanabe, Mitsuteru Asai, Coupling simulator between chemical diffusion and crack propagation by a Voxel FEM incorporated with the Damage Mechanics, Transactions of the Japan Society for Computational Engineering and Science, 2013, 2013.01, Alkali Silica Reaction (ASR), chloride damage of reinforced steel and other aging degradations in concrete structures are strongly dependent on both of chemical phenomena and mechanical behavior including fracture. In this study, a coupling simulator has been developed in order to investigate the degradation mechanism of these concrete aging damages. In the coupling simulator, non-stationary diffusion analysis for Alkali ion is solved firstly, and then the expansion force act on the aggregate is evaluated by referring consistency of the alkali ion. In the second step, nonlinear damage analysis is conducted. The nonlinear damage analysis evaluates cracking region with the damage parameter. The following diffusion analysis changes diffusion coefficient in the cracking region by referring the damage parameter. The above procedures are coupled at each time step. © 2013 by the Japan Society for Computational Engineering and Science..
92. Mitsuteru Asai, Keisuke Fujimoto, Shoichi Tanabe, Masuhiro Beppu, Slip and no-slip boundary treatment for particle simulation model with incompatible step-shaped boundaries by using a virtual maker, Transactions of the Japan Society for Computational Engineering and Science, 2013, 1, 2013.01, Particle method such as Smoothed Particle Hydrodynamics (SPH) and Moving Particle Semi-implicit method (MPS) can handle quite complicated physical problems involving dynamic changes of free surface and crack propagation, and it is wildly expanding its applications not only in the fluid dynamics but also in the solid mechanics. Beside of these advantages, particle methods are not so easy to treat boundary conditions, like pressure Neumann condition and slip or no-slip condition in fluid dynamics. This is one of the typical difficulties in mesh-less type method. In addition, particle simulation model may include an incompatible step-shaped boundary line, which is made by using a simple pre-processing of particle model. Although the simple and robust pre-processing is one of the advantage of particle simulation, the step-shaped boundary may generate un-realistic numerical solution across the real boundary line especially in the fluid dynamics. Recently, pressure Neumann condition in SPH is re-focused with fixed ghost boundary method using virtual makers. In this paper, the fixed ghost boundary method is modified to treat the incompatible step-shaped boundary particles by referring the real physical boundary line. The accuracy and efficiencies of proposed method are validated by comparison between a numerical solution and experimental results. © 2013 by the Japan Society for Computational Engineering and Science..
93. Akane Watanabe, Mitsuteru Asai, Coupling simulator between chemical diffusion and crack propagation by a Voxel FEM incorporated with the Damage Mechanics, Transactions of the Japan Society for Computational Engineering and Science, 2013, 2013.01, Alkali Silica Reaction (ASR), chloride damage of reinforced steel and other aging degradations in concrete structures are strongly dependent on both of chemical phenomena and mechanical behavior including fracture. In this study, a coupling simulator has been developed in order to investigate the degradation mechanism of these concrete aging damages. In the coupling simulator, non-stationary diffusion analysis for Alkali ion is solved firstly, and then the expansion force act on the aggregate is evaluated by referring consistency of the alkali ion. In the second step, nonlinear damage analysis is conducted. The nonlinear damage analysis evaluates cracking region with the damage parameter. The following diffusion analysis changes diffusion coefficient in the cracking region by referring the damage parameter. The above procedures are coupled at each time step. © 2013 by the Japan Society for Computational Engineering and Science..
94. Mitsuteru Asai, Keisuke Fujimoto, Shoichi Tanabe, Masuhiro Beppu, Slip and no-slip boundary treatment for particle simulation model with incompatible step-shaped boundaries by using a virtual maker, Transactions of the Japan Society for Computational Engineering and Science, 10.11421/jsces.2013.20130011, 2013, 1-20130011, 2013.01, Particle method such as Smoothed Particle Hydrodynamics (SPH) and Moving Particle Semi-implicit method (MPS) can handle quite complicated physical problems involving dynamic changes of free surface and crack propagation, and it is wildly expanding its applications not only in the fluid dynamics but also in the solid mechanics. Beside of these advantages, particle methods are not so easy to treat boundary conditions, like pressure Neumann condition and slip or no-slip condition in fluid dynamics. This is one of the typical difficulties in mesh-less type method. In addition, particle simulation model may include an incompatible step-shaped boundary line, which is made by using a simple pre-processing of particle model. Although the simple and robust pre-processing is one of the advantage of particle simulation, the step-shaped boundary may generate un-realistic numerical solution across the real boundary line especially in the fluid dynamics. Recently, pressure Neumann condition in SPH is re-focused with fixed ghost boundary method using virtual makers. In this paper, the fixed ghost boundary method is modified to treat the incompatible step-shaped boundary particles by referring the real physical boundary line. The accuracy and efficiencies of proposed method are validated by comparison between a numerical solution and experimental results. © 2013 by the Japan Society for Computational Engineering and Science..
95. Naoki Takano, Mitsuteru Asai, Kohta Okamoto, Monte Carlo simulation of dynamic problem using model order reduction technique highlighting on tail probability, Journal of Solid Mechanics and Materials Engineering, 6, 3, 169-181, 2012.09.
96. Mitsuteru Asai, Multi-scale modeling in heterogeneous material properties, MI Lecture Note Series, 39, 84-95, 2012.09.
97. Mitsuteru Asai, Keisuke Fujimoto, Abdelraheem M. Aly, Yoshimi Sonoda, Fluid-Soil-Structure coupling analysis for tsunami disaster simulation, Proceeding of KSME-JSME joint symposium on computational mechanics & CAE 2012, 11-16, 2012.09.
98. 浅井光輝, 上坂隆志,園田佳巨,西本安志,西野好生, 都市型水害対策用ゴム製止水構造の非線形有限要素解析とその検証, 土木学会論文集A2(応用力学), Vol. 68, No.2, I_353-I_360, 2012.09.
99. Mitsuteru ASAI, Abdelraheem M. ALY, Yoshimi SONODA, Yuzuru SAKAI , A stabilized incompressible SPH method by relaxing the density invariant condition, Journal of Applied Mathematics, Volume 2012 (2012), Article ID 139583, 24 pages, 2012.04.
100. 浅井光輝,別府万寿博,石川信隆,眞鍋慶生,斉藤展,丹羽一邦, 数値流体シミュレーションによる流体衝撃力評価に関する基礎的研究, 構造工学論文集, 58, 1021-1028, 2012.03.
101. Abdelraheem M. ALY, Mitsuteru ASAI, Yoshimi SONODA , A study of violent water induced impact problems using ISPH method
, Proceeding of 9th International Conference on Shock & Impact Loads on Structures, 217-224, 2011.11.
102. Nobutaka ISHIKAWA, Masuhiro BEPPU, Tsutomu MIKAMI, Hiroshi TATESAWA, Mitsuteru ASAI , Collapse mechanism of seawalls by impulsive load due to the March 11 tsunami
, Proceeding of 9th International Conference on Shock & Impact Loads on Structures, 1-12, 2011.11.
103. Mitsuteru Asai, Hiroki Iida, Norliyati M. Amin and Yoshimi Sonoda , Fast dynamic solver for the design of bridge using a model order reduction
, Proceeding of 9th International Conference on Shock & Impact Loads on Structures, 225-234, 2011.11.
104. Mitsuteru ASAI, Estimation of water-induced impact force during TSUNAMI by a stabilized SPH simulation, Proceedings of International Symposium on Disaster Simulation & Structural Safety in the Next Generation 2011, 133-138, 2011.09.
105. Abdelraheem M. ALY, Mitsuteru ASAI and Yoshimi SONODA, Floating rigid body simulation in free surface flow using a stabilized incompressible SPH method, Proceedings of the 2011 World Congress on Advances in Structural Engineering and Mechanics, 4460-4469, 2011.09.
106. Mitsuteru ASAI, Akane WATANABE, Yoshimi SONODA, Development of a 3D coupling simulator between chemical diffusion and nonlinear mechanics in meso-scopic concrete, Proceedings of the 2011 World Congress on Advances in Structural Engineering and Mechanics, 3515-3523, 2011.09.
107. Abdelraheem M. Aly, Mitsuteru Asai, Yoshimi Sonoda, Simulation of free falling rigid body into water by a stabilized incompressible SPH method, Ocean Systems Engineering, Vol. 1, No. 3, 2011.08.
108. Mitsuteru Asai,Norliyati M. Amin, Yoshimi Sonoda, Practical determination of an effective reduced order in a model order reduction of dynamic FEM via Krylov subspace, 応用力学論文集, Vol.14, 2011.08.
109. Mitsuteru Asai, Abdelraheem M. Aly, Yoshimi Sonoda, ISPH-FEM coupling simulator for the FSI problems, Proceeding of the 6th SPHERIC SPH workshop, pp.201-208, 2011.06.
110. Mitsuteru Asai, Yoshiyuki Kimura, Yoshimi Sonoda, Yasushi Nishimoto, Yoshio Nishino, Constitutive modeling for texture reinforced rubber by using an anisotropic visco-hyperelastic model, Doboku Gakkai Ronbunshuu A, 10.2208/jsceja.66.194, 66, 194-205, 2010.12, Fabric reinforced rubber shows an anisotropy and viscosity in wide strain range. In this paper, an anisotropic visco-elastic model based on Mooney-Rivlin model is developed for fabric reinforced rubber. Anisotropy is introduced, in this constitutive model, by using a structure tensor that shows direction of reinforced fiber. A new strain energy density function for anisotropic elasticity is proposed to improve accuracy associated with shear behaviors. After developing an elastic model, an anisotropic viscosity is modeled by a kind of Maxwell viscosity model at large strains. In addition to the development of constitutive model, a simple fracture prediction method, which refers to the finite element solution incorpolated with our proposed constitutive model, is proposed. Finally, our proposed constitutive model and fracture prediction method are validated with comparisons of uni-axial tension tests with fabric reinforced rubber..
111. Mitsuteru Asai, Yoshiyuki Kimura, Yoshimi Sonoda, Yasushi Nishimoto, Yoshio Nishino, Constitutive modeling for texture reinforced rubber by using an anisotropic visco-hyperelastic model, Doboku Gakkai Ronbunshuu A, 10.2208/jsceja.66.194, 66, 2, 194-205, 2010.12, Fabric reinforced rubber shows an anisotropy and viscosity in wide strain range. In this paper, an anisotropic visco-elastic model based on Mooney-Rivlin model is developed for fabric reinforced rubber. Anisotropy is introduced, in this constitutive model, by using a structure tensor that shows direction of reinforced fiber. A new strain energy density function for anisotropic elasticity is proposed to improve accuracy associated with shear behaviors. After developing an elastic model, an anisotropic viscosity is modeled by a kind of Maxwell viscosity model at large strains. In addition to the development of constitutive model, a simple fracture prediction method, which refers to the finite element solution incorpolated with our proposed constitutive model, is proposed. Finally, our proposed constitutive model and fracture prediction method are validated with comparisons of uni-axial tension tests with fabric reinforced rubber..
112. Norliyati Mohd Amin, Mitsuteru Asai, Yoshimi Sonoda, Fast transient structural FE analysis imposing prescribed displacement condition by using a model order reduction method via Kryrov subspace, 応用力学論文集, 13, 159-167, 2010.08.
113. Norliyati Mohd Amin, Mitsuteru Asai, Yoshimi Sonoda, Application of a model order reduction based on the Kryrov subspace to finite element transient analysis imposing several kinds of boundary condition, IOP conf. ser. : Material Science and Engineering,, 10, 012118, 2010.05.
114. 浅井光輝,木村嘉之,園田佳巨,西本安志,西野好生, 異方性を考慮した超弾性・粘性体による織布補強ゴムの力学モデリング, 土木学会論文集A, 66, 2010.03.
115. Mitsuteru Asai, Takanori Hayashi, Yoshimi Sonoda, Numerical estimation of water-induced impact pressure by using a smoothed particle hydrodynamics for incompressible flow, Proceedings of Protect2009, 2009.08.
116. 浅井光輝,山下和也,山崎礼智,荒木和哉, 離散型有限要素モデルによる石造橋の静的・動的強度特性評価, 構造工学論文集, Vol.55A,pp.172-180, 2009.04.
117. Atsushi Sando, Naoki Takano, Mitsuteru Asai, Toshiyuki Toriyama, Syoji Kido, Jan G. Korvink, Reduction of finite element mesh and model order for fast dynamic analysis of global/local problem, Journal of Solid Mehcnics and Material Engineering, Vol.3, No. 3, pp. 572-583, 2009.03.
118. 高野 直樹, Reduction of Finite Element Mesh and Model Order for Fast Dynamic Analysis of Global/Local Problem, Jurnal of Solid Mechanics and Materials Engineering, 3, 3, 572-583, 2009.03.
119. 高野 直樹, Reduction of Finite Element Mesh and Model Order for Fast Dynamic Analysis of Global/Local Problem, Jurnal of Solid Mechanics and Materials Engineering, 10.1299/jmmp.3.572, 3, 3, 572-583-583, 2009.03, MEMS structures and machines fabricated by photolithography and/or etching have often repeated unit microstructure. We need to design not only the global parameters but also microscopic and local parameters. In pursuit of this, a dynamic analysis of global/local problem is essential, and especially fast computational method and convenient modeling technique are both required for the MEMS design. Hence, this paper presents the application of model order reduction (MOR) for fast dynamic analysis combined with the finite element mesh superposition (FEMS) technique for practical and convenient modeling of the above-mentioned microstructures. Through two examples, the accuracy is carefully investigated for both global and local responses associated with the base vectors in MOR algorithm. The first example is analyzed by a kind of homogenization technique and MOR. The number of DOFs was finally reduced by a factor of approximately 1/6 (47,362/296,268). In addition, MOR enabled us to reduce the coefficient matrix size to only 300. The second example is analyzed by both FEMS and MOR, and it was found that MOR is also applicable to an unusual matrices generated by FEMS..
120. 浅井光輝,木村嘉之,西本安志,西野好生,園田佳巨, 異方性超弾性モデルによる織布強化ゴム特性の数値解, 応用力学論文集, Vol.11,pp.467-474, 2008.10.
121. Mitsuteru ASAI, Kenjiro TERADA and Atsushi MARUYAMA, Eulerian Finite Cover Method for multi-scale analysis of large deformed composites, 8 th World Congress on Computational Mechanics, 2008.07.
122. 高野直樹,浅井光輝,黄田尚宏,橋本和信, ナノ粒子分散材の3次元モルフォロジー分析と有限要素モデリング, 日本材料学会,材料, 2008.05.
123. Mitsuteru Asai, Naoki Takano, Yasutomo Uetsuji, Kunihiko Taki, An iterative solver applied to strongly coupled piezoelectric problems of porous Pb(Zr,Ti)O-3 with nondestructive modelling of microstructure, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 10.1088/0965-0393/15/6/002, 15, 6, 597-617, 2007.09, A new preconditioned iterative solver based on the Kryrov subspace method is developed for solving large-scale finite element (FE) models of piezoelectric problems. The system matrix of piezoelectric FE analysis has negative eigenvalues because of coupling terms between mechanical and electrical fields. A general preconditioned iterative solver is ineffective for large-scale piezoelectric FE analysis due to the indefinite system matrix. A block diagonal preconditioner for the piezoelectric finite element method (FEM) is proposed by grouping nodal values as a block. Then the proposed solver is applied to the homogenization method, which can evaluate the effective macroscopic material properties by using FEM. In the FE modelling of complex microstructures, a semi-automatic technique with nondestructive observation provides reasonable 3D micrographs of porous Pb(Zr, Ti)O-3 (PZT). The efficiency of the proposed solver is investigated through the homogenization analysis of real porous PZT samples..
124. Mitsuteru Asai, Naoki Takano, Yasutomo Uetsuji, Kunihiko Taki, An iterative solver applied to strongly coupled piezoelectric problems of porous Pb(Zr,Ti)O-3 with nondestructive modelling of microstructure, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 10.1088/0965-0393/15/6/002, 15, 6, 597-617, 2007.09, A new preconditioned iterative solver based on the Kryrov subspace method is developed for solving large-scale finite element (FE) models of piezoelectric problems. The system matrix of piezoelectric FE analysis has negative eigenvalues because of coupling terms between mechanical and electrical fields. A general preconditioned iterative solver is ineffective for large-scale piezoelectric FE analysis due to the indefinite system matrix. A block diagonal preconditioner for the piezoelectric finite element method (FEM) is proposed by grouping nodal values as a block. Then the proposed solver is applied to the homogenization method, which can evaluate the effective macroscopic material properties by using FEM. In the FE modelling of complex microstructures, a semi-automatic technique with nondestructive observation provides reasonable 3D micrographs of porous Pb(Zr, Ti)O-3 (PZT). The efficiency of the proposed solver is investigated through the homogenization analysis of real porous PZT samples..
125. S. Manchiraju, Mitsuteru Asai, S. Ghosh, A dual-time-scale finite element model for simulating cyclic deformation of polycrystalline alloys, Journal of Strain Analysis for Engineering Design, 10.1243/03093247JSA233, 42, 4, 183-200, 2007.08, [URL], A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time-scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime-scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation..
126. Mitsuteru Asai, Naoki Takano, Yasutomo Uetsuji, Kunihiko Taki, An iterative solver applied to strongly coupled piezoelectric problems of porous Pb(Zr.Ti)O3 with nondestructive modeling of microstructure, Modeling and Simulation in Metarial Science and Engineering, Vol. 15, pp. 597-617, 2007.07.
127. S. Manchiraju, M. Asai, S. Ghosh, A dual-time-scale finite element model for simulating cyclic deformation of polycrystalline alloys, JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, 10.1243/03093247JSA233, 42, 4, 183-200, 2007.04, A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time -scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime- scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation..
128. S. Manchiraju, M. Asai, S. Ghosh, A dual-time-scale finite element model for simulating cyclic deformation of polycrystalline alloys, JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, 10.1243/03093247JSA233, 42, 4, 183-200, 2007.04, A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time -scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime- scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation..
129. 浅井光輝、高野直樹、滝邦彦、足森崇志、日下貴之、上辻靖智, 均質化法による多孔質圧電材料のイメージベース・マルチスケール解析, 日本材料学会、材料, Vol. 55, No.12, pp. 1111-1116, 2006.12.
130. 浅井 光輝, 高野 直樹, 滝 邦彦, 足森 崇志, 日下 貴之, 上辻 靖智, 均質化法による多孔質圧電材料のイメージベース・マルチスケール解析, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.1111, 55, 12, 1111-1116, 2006.12, This paper presents an image-based multi-scale analysis in order to evaluate macroscopic properties of heterogeneous porous piezoelectric materials by finite element calculations. The multi-scale analysis is based on the mathematical homogenization theory. Material heterogeneity is represented as a micro structure FE model that is automatically generated from the cross-sectioned images by high resolution X-ray CT. The high resolution X-ray measurement for porous PZT is compared with the digital image of SEM. Radius of pore is quantified from their images to compare these images. Nodal blocking preconditioned iterative solver is developed for piezoelectric FEM with high degree of freedom. In the numerical examples, material properties of porous PZT materials with different porosity are evaluated by the image-based multi-scale analysis to show the applicability and efficiency. Image-based multi-scale analysis with one million elements can be conducted by conventional PC with help of the proposed iterative solver..
131. 浅井 光輝, 高野 直樹, 滝 邦彦, 足森 崇志, 日下 貴之, 上辻 靖智, 均質化法による多孔質圧電材料のイメージベース・マルチスケール解析, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.1111, 55, 12, 1111-1116, 2006.12, This paper presents an image-based multi-scale analysis in order to evaluate macroscopic properties of heterogeneous porous piezoelectric materials by finite element calculations. The multi-scale analysis is based on the mathematical homogenization theory. Material heterogeneity is represented as a micro structure FE model that is automatically generated from the cross-sectioned images by high resolution X-ray CT. The high resolution X-ray measurement for porous PZT is compared with the digital image of SEM. Radius of pore is quantified from their images to compare these images. Nodal blocking preconditioned iterative solver is developed for piezoelectric FEM with high degree of freedom. In the numerical examples, material properties of porous PZT materials with different porosity are evaluated by the image-based multi-scale analysis to show the applicability and efficiency. Image-based multi-scale analysis with one million elements can be conducted by conventional PC with help of the proposed iterative solver..
132. 河貝光寛、高野直樹、中野貴由、浅井光輝, 海面骨の骨梁モルフォロジーと生体アパタイト結晶配向性を考慮したマルチスケール応力解析, 日本材料学会、材料, Vol.55, No.2, pp.874-880, 2006.09.
133. 河貝 光寛, 高野 直樹, 中野 貴由, 浅井 光輝, 海綿骨の骨梁モルフォロジーと生体アパタイト結晶配向性を考慮したマルチスケール応力解析, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.874, 55, 9, 874-880, 2006.09, This paper presents the multi-scale stress analysis of trabecular bone by the homogenization method bridging nano-micro-macro scales. Three-dimensional microstructure of trabeculae is obtained by the X-ray CT and the image-based modeling technique. Biological apatite (BAp) crystallite orientation is considered in the microstructure model by means of the anisotropic mechanical properties. The c-axis of BAp is set up as the maximum principal stress direction under the long term macroscopic stress condition. These properties are automatically assigned to each voxel element. To determine appropriately the microstructure model, the trabeculae morphology is analyzed and quantified as the trabecular density distribution. The proposed method is applied to pig's femur. It was revealed by the morphology analysis and homogenized macroscopic properties that the trabecular bone has plate-like characteristics. The predicted anisotropic level of the macroscopic properties was quantitatively coincident with the measured value by the X-ray diffraction analysis..
134. 河貝 光寛, 高野 直樹, 中野 貴由, 浅井 光輝, 海綿骨の骨梁モルフォロジーと生体アパタイト結晶配向性を考慮したマルチスケール応力解析, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.874, 55, 9, 874-880, 2006.09, This paper presents the multi-scale stress analysis of trabecular bone by the homogenization method bridging nano-micro-macro scales. Three-dimensional microstructure of trabeculae is obtained by the X-ray CT and the image-based modeling technique. Biological apatite (BAp) crystallite orientation is considered in the microstructure model by means of the anisotropic mechanical properties. The c-axis of BAp is set up as the maximum principal stress direction under the long term macroscopic stress condition. These properties are automatically assigned to each voxel element. To determine appropriately the microstructure model, the trabeculae morphology is analyzed and quantified as the trabecular density distribution. The proposed method is applied to pig's femur. It was revealed by the morphology analysis and homogenized macroscopic properties that the trabecular bone has plate-like characteristics. The predicted anisotropic level of the macroscopic properties was quantitatively coincident with the measured value by the X-ray diffraction analysis..
135. 高野直樹、浅井光輝、大山龍男、小川孝行, 材料・構造のシミュレーションベースデザイン, 日本材料学会 材料, Vol.55, No.2, pp.237-242, 2006.02.
136. 高野 直樹, 浅井 光輝, 大山 龍男, 小川 孝行, 実用化期の複合材料技術と課題 : 2. 材料・構造のシミュレーションベース・デザイン, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.237, 55, 2, 237-242, 2006.02.
137. 高野 直樹, 浅井 光輝, 大山 龍男, 小川 孝行, 実用化期の複合材料技術と課題 : 2. 材料・構造のシミュレーションベース・デザイン, 材料 = JOURNAL OF THE SOCIETY OF MATERIALS SCIENCE, JAPAN, 10.2472/jsms.55.237, 55, 2, 237-242, 2006.02.
138. Kenjiro Terada, Mitsuteru Asai, Finite cover method for physically and geometrically nonlinear problems, Lecture Notes in Computational Science and Engineering, 43, 169-190, 2005.12.
139. 浅井光輝、山岸道弘、寺田賢二郎、永井学志, 非局所ボクセル有限要素法の開発とその破壊挙動解析への適用, 土木学会論文集I, No.759/I-67, pp.233-245, 2005.04.
140. Kenjiro Terada, Mitsuteru Asai, Finite cover method for physically and geometorically nonlinear problems, Lecture Notes on Computaional Science and Engineering, Vol.43, pp.169-190, 2005.01.
141. Mitsuteru Asai, Somnath Ghosh, Temporal homogenization for crystal plasticity, AIP Conference Proceedings, Vol. 712, pp.1725-1730, 2004.06.
142. 浅井 光輝, 山岸 道弘, 寺田 賢二郎, 永井 学志, 非局所型ボクセル有限要素法の開発とその破壊挙動解析への適用, 土木学会論文集 = Proceedings of JSCE, 10.2208/jscej.2004.759_233, 759, 233-245, 2004.04, 従来のボクセル解析における材料界面での人工的な応力振動を回避するために積分平均化理論を導入する非局所型ボクセル有限要素法を提案し, 任意方向に進展する不連続面の取り扱いが簡便であるエレメント除去技術を導入して不連続面進展解析手法へと拡張する. 非局所変数の算定方法, 破壊基準, 不連続面進展の解析アルゴリズムなどについて述べた後, 数値解析例を示して手法の妥当性・適用性を検証する. 特に, 材料界面における応力振動の問題だけでなく, 要素除去に起因する要素寸法依存性に対しても積分平均化理論を適用して算出する非局所ひずみ・応力が有効に機能することを示す. また, コンクリート材料のような非均質脆性材料を想定して, 微視的な非均質性に起因した不連続面進展挙動やその強度特性を表す2軸破壊包絡線の再現を試みる..
143. Kenjiro Terada, Mitsuteru Asai, Michihiro Yamagishi, Finite cover method for linear and nonlinear analysis of heterogeneous solids, International Journal of Numerical Methods in Engineering, Vol.58, pp.1321-1346, 2003.11.
144. K Terada, M Asal, M Yamagishi, Finite cover method for linear and non-linear analyses of heterogeneous solids, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, 10.1002/nme.820, 58, 9, 1321-1346, 2003.11, We introduce the finite cover method (FCM) as a generalization of the finite element method (FEM) and extend it to analyse the linear and non-linear mechanical behaviour of heterogeneous solids and structures. The name 'FCM' is actually an alias for the manifold method (MM) and the basic idea of the method has already been established for linear analyses of structures with homogeneous materials. After reviewing the concept of physical and mathematical covers for approximating functions in the FCM, we present the formulation for the static equilibrium state of a structure with arbitrary physical boundaries including material interfaces. The problem essentially involves the discontinuities in strains, and possibly has the discontinuities in displacement caused by interfacial debonding or rupture of material interfaces. We simulate such non-linear mechanical behaviour after presenting simple numerical examples that demonstrate the equivalence between the approximation capabilities of the FCM and those of the FEM. Copyright (C) 2003 John Wiley Sons, Ltd..
145. K Terada, M Asal, M Yamagishi, Finite cover method for linear and non-linear analyses of heterogeneous solids, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, 10.1002/nme.820, 58, 9, 1321-1346, 2003.11, We introduce the finite cover method (FCM) as a generalization of the finite element method (FEM) and extend it to analyse the linear and non-linear mechanical behaviour of heterogeneous solids and structures. The name 'FCM' is actually an alias for the manifold method (MM) and the basic idea of the method has already been established for linear analyses of structures with homogeneous materials. After reviewing the concept of physical and mathematical covers for approximating functions in the FCM, we present the formulation for the static equilibrium state of a structure with arbitrary physical boundaries including material interfaces. The problem essentially involves the discontinuities in strains, and possibly has the discontinuities in displacement caused by interfacial debonding or rupture of material interfaces. We simulate such non-linear mechanical behaviour after presenting simple numerical examples that demonstrate the equivalence between the approximation capabilities of the FCM and those of the FEM. Copyright (C) 2003 John Wiley Sons, Ltd..
146. 車谷麻緒、浅井光輝、寺田賢二郎, 有限被覆法の弾塑性問題への適用とその性能評価, 土木学会、応用力学論文集, Vol.6, pp.247-256, 2003.08.
147. 浅井光輝、寺田賢二郎, 有限被覆法による不連続面進展解析, 土木学会、応用力学論文集, Vol.6, pp.193-200, 2003.08.
148. Mitsuteru Asai, Kenjiro Terada, Kiyohiro Ikeda, Hiroyuki Suyama, Katashi Fujii, Meso-scopic numerical analysis of concrete structures by a modified lattice model, 土木学会論文集I, Vol.20, No.1, pp.43-54, 2003.04.
149. Mitsuteru Asai, Kenjiro Terada, Kiyohiro Ikeda, Hiroyuki Suyama, Katashi Fujii, Meso-scopic numerical analysis of concrete structures by a modified lattice model, Structural Engineering/Earthquake Engineering, 10.2208/jsceseee.20.43s, 20, 731, 19-30, 2003.04, Realistic simulation of the mechanical behavior of concrete and reinforced concrete structures is performed by using a lattice type numerical model. Five different types of lattice members with simple constitutive models are introduced for mortar, coarse aggregate, steel, aggregate-mortar interface and steel-concrete interface. The meso-scopic morphology of concrete, which can be realized by the image-based geometry modeling technique, is taken into account. By the incorporation of the accurate meso-scopic morphology into the lattice type numerical modeling, the cracking behavior induced by the meso-scopic heterogeneities has been successfully captured..
150. Mitsuteru Asai, Kenjiro Terada, Kiyohiro Ikeda, Hiroyuki Suyama, Katashi Fujii, Meso-scopic numerical analysis of concrete structures by a modified lattice model, Structural Engineering/Earthquake Engineering, 10.2208/jsceseee.20.43s, 20, 731, 19-30, 2003.04, Realistic simulation of the mechanical behavior of concrete and reinforced concrete structures is performed by using a lattice type numerical model. Five different types of lattice members with simple constitutive models are introduced for mortar, coarse aggregate, steel, aggregate-mortar interface and steel-concrete interface. The meso-scopic morphology of concrete, which can be realized by the image-based geometry modeling technique, is taken into account. By the incorporation of the accurate meso-scopic morphology into the lattice type numerical modeling, the cracking behavior induced by the meso-scopic heterogeneities has been successfully captured..
151. 浅井 光輝, 寺田 賢二郎, 池田 清宏, ラチスモデルによるコンクリート構造のメゾレベル解析, 土木学会論文集, 10.2208/jscej.2003.731_19, 731, 19-30, 2003.04.
152. 浅井光輝、寺田賢二郎, マルチスケールモデリングに基づく非均質脆性材料の強度評価法, 土木学会 応用力学論文集, Vol.5, pp.217-226, 2002.08.
153. 北川智弘、有尾一郎、浅井光輝、池田清宏, ラチスモデルによる材料のせん断破壊シミュレーション, 土木学会、応用力学論文集, Vol.3,pp.277-284, 2001.08.
154. 浅井光輝、寺田賢二郎、池田清宏、山岸道弘, Hybrid-FEMの開発とその多相材料の界面破壊解析への適用, 土木学会 応用力学論文集, Vol.5, pp.217-226, 2001.08.
155. Mitsuteru Asai, Kenjiro Terada, Kiyohiro Ikeda, Meso-scopic concrete analysis with a lattice model, Proceeding of FRAMCOS-4, A.A. Publishers, pp.757-764, 2001.05.
156. 菅野友紀、浅井光輝、池田清宏、寺田賢二郎、小田憲史, トラス構造物に対する静的座屈強度の確率評価法, 土木学会 応用力学論文集, Vol.2, pp.37-42, 1999.08.
157. 浅井光輝、藤井文夫、池田清宏, 群対称性のある構造分岐問題における固有ベクトルを用いたReduction法, 構造工学論文集, Vol.45A, pp.263-270, 1999.03.

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