Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Wang, Z.; 松本 俊慶; Duan, G.*; 松永 拓也*
Computer Methods in Applied Mechanics and Engineering, 414, p.116168_1 - 116168_49, 2023/09
被引用回数：3 パーセンタイル：89.18(Engineering, Multidisciplinary)Recently, consistent meshfree particle methods have been intensively studied. It has been pointed out that numerical inaccuracy or instability could easily occur with incomplete or biased neighbor support. This study proposes a new meshfree particle method called the compact moving particle semi-implicit (CMPS) method to decrease the condition number. In the proposed CMPS, the first-order and second-order derivatives are discretized separately, enhancing the numerical stability significantly. By adopting a small dilation parameter of the compact support, the CMPS can remarkably improve accuracy and reduce computational costs. Formulations for zeroth-order, first-order, and second-order derivatives are derived, and various boundary conditions, e.g., Dirichlet and Neumann, are discussed. In order to better deal with complex free-surface flows using the CMPS, some new numerical techniques, i.e., optimized regularization and reconstructed particle shifting schemes, are also developed. Furthermore, the surface fitting method is extended to address the surface tension. A convergence study is conducted in complex geometry to verify the stability, accuracy, and efficiency of the CMPS. Then, second-order accuracy is confirmed using the Taylor-Green vortex problem. After that, numerical examples concerning various free-surface flows, including square patch, hydrostatic pressure, dam break, droplet oscillation, and droplet coalescence, are calculated to demonstrate the potential of the CMPS.
Wang, Z.; 杉山 智之; 松永 拓也*; 越塚 誠一*
Computers & Fluids, 247, p.105646_1 - 105646_21, 2022/10
被引用回数：1 パーセンタイル：20.8(Computer Science, Interdisciplinary Applications)This paper develops a highly accurate, multi-resolution particle method to simulate solid-liquid phase change coupled with the thermal flow. Instead of including the latent heat in the governing equation, the heat equations for solid and liquid phases are solved separately. A sharp interface model is proposed to represent the solid-liquid interface explicitly. The sharp interface, represented by discrete nodes, provides the Neumann boundary condition for pressure and the Dirichlet boundary condition for velocity/temperature, respectively. Based on temperature gradients in the solid and liquid phases, the positions of these interface nodes are updated every time step. The Eulerian-based formulation, rather than the conventional Lagrangian-based one, is utilized to minimize time step-dependent error. Up to 4th order spatial discretization scheme is adopted based on the Least Square Moving Particle Semi-implicit (LSMPS) scheme. Moreover, a geometry-based multi-resolution scheme is introduced to dynamically refine the spatial resolution near the interface for saving computational cost. The 1-D Stefan problem is firstly simulated to verify the accuracy of the proposed sharp interface model. Then, the consistency of the multi-resolution scheme is investigated by a convergence study of the Taylor-Green vortex problem. After that, numerical simulations of natural convection in a cavity are performed with different spatial resolutions and high order schemes. Resulted computational costs are compared and discussed. Finally, the problems of melting by natural convection with different Rayleigh numbers are investigated. The results achieved so far indicate that the multi-resolution and high order schemes have great potential to save computational cost.
Wang, Z.; Duan, G.*; 松永 拓也*; 杉山 智之
International Journal of Heat and Mass Transfer, 157, p.119919_1 - 119919_20, 2020/08
被引用回数：16 パーセンタイル：77.06(Thermodynamics)Enforcing accurate and consistent boundary conditions is a difficult issue for particle methods, due to the lack of information outside boundaries. Recently, consistent Neumann boundary condition enforcement is developed for the least squares moving particle semi-implicit method (LSMPS). However, the Robin boundary cannot be straightforwardly considered by that method because no computational variables are defined on the wall boundary. In this paper, a consistent Robin boundary enforcement for heat transfer problem is proposed. Based on the Taylor series expansion, the Robin boundary condition for temperature is converted to the fitting function of internal rather than boundary particles and incorporated into least squares approach for discretization schemes. Arbitrary geometries can be easily treated due to the use of polygons for wall boundary. A convergence study was firstly carried out to verify the consistency. Then, numerical tests of 1-D and 2-D heat conduction problems subjected to mixed boundary conditions were performed for verification, and good agreements with theoretical solutions were observed. Natural convection problems with different boundary conditions in an annulus were carried out for further validations of heat-fluid coupling. Excellent agreements between the present and literature results were demonstrated.
西村 昭彦; 羽成 敏秀; 中村 将輝; 松永 幸大; 下村 拓也; 大道 博行; 中井 宏二; 山田 大地; 井崎 賢二; 川妻 伸二
no journal, ,
平成27年度の原子力機構での夏期休暇実習生制度の実施内容のうち、遠隔技術として深く関連する要素技術としてロボット技術及びレーザー応用技術について実施報告を行う。廃止措置技術の中核となる遠隔技術開発では、ロボット、放射線計測、レーザー応用等の幅広い先端技術に取り組める人材を養成することを目的とする。ロボットについては、原子炉構造に合わせた特殊形状のロボット開発が福島原子力発電所の現場で進められている。これまで、原子力機構でも遠隔操作可能なロボットを開発した。これは、移動のためのクローラと作業のためのアームを備えている。この基本機能とその操作に習熟する学習内容とした。また、高出力レーザーの適用はロボットへのセンサー搭載に続く先のことになる。レーザー切断が可能となれば、加熱による溶融と高速ガスによる溶融部分の除去により切断が進むことを模擬実験により学習した。平成28年度は楢葉地区での活動に傾注する。このため、大学・高等専門学校側の教育内容と受け入れ側である原子力機構の実施内容の刷りあわせが重要である。
