著者

梶島 岳夫

出版者

公益財団法人 日本学術協力財団

雑誌

学術の動向 (ISSN:13423363)

巻号頁・発行日

vol.19, no.10, pp.10_54-10_57, 2014-10-01 (Released:2015-02-06)

参考文献数

5

著者

梶島 岳夫

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.60, no.574, pp.2058-2063, 1994-06-25 (Released:2008-03-28)

参考文献数

16

被引用文献数

29 33

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A proper finite difference method based on the gradient/convective form of the equation of motion of incompressible fluid is discussed. The gradient form discretized on the staggered grid has essentially the same conservation properties as those of the divergence/momentum-conservative form or the quadratic-conservative form under some conditions. First, the mass continuity should be numerically satisfied. Second, the numerical consistency between the mass continuity and the momentum convection should be satisfied. The gradient form evaluated at midpoints between velocity points in the direction of convection, rather than directly calculated at velocity points, meets this requirement. In this paper, through mathematical description of the above-mentioned features, the performance of the higher-order finite difference method for the gradient form is demonstrated.

著者

梶島 岳夫 太田 貴士 岡崎 和彦 三宅 裕

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.63, no.614, pp.3247-3254, 1997-10-25 (Released:2008-03-28)

参考文献数

25

被引用文献数

13 13

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To apply the direct numerical simulation (DNS) and the large-eddy simulation (LES) of turbulence to flow fields of complicated geometry, a higher-order finite-difference method (FDM) has been developed for the body-fitted coordinate system. The consistency and the conservation property of FDMs are discussed for the collocated grid. As numerical examples, DNS results of decaying isotropic turbulence and DNS/LES results for plane channel flow are shown and the influence of variable arrangement is examined. The results by the consistent 'interpolation' method for gradient form on the collocated grid agree well with those by other proper FDMs and the spectral method.

著者

中出 孝次 佐久間 豊 梶島 岳夫

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.87, no.893, pp.20-00366, 2021 (Released:2021-01-25)

参考文献数

11

被引用文献数

1 1

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To clarify the mechanisms underlying airflow-induced vibrations of high-speed trains running through tunnels, large-eddy simulation of a large-scale flow structure around a simplified 6-car train model was conducted. Since actual trains run on one of the double track lines, the position of the train model was made to deviate from the tunnel center and hence the gap between one of the sides of the train and the tunnel wall is narrower than that of the other side. A train running in the open air was also calculated for comparison. The results of this study shed light on the generation mechanism of the pressure fluctuations acting on the side of high-speed trains as follows. Firstly, in the open air, the air velocity in the space between the underbody and the ground gradually decreases from the head toward the tail of the train. Thus, the air velocity is slower than that on both sides of the train, which generates shear flows near the bottom edges of both sides of the train. The shear flows cause large Karman vortex-like vortices (staggered Karman vortex street), which in turn lead to a meandering airflow beneath the underbody of the train. Secondly, in the tunnel, the air velocity not only in the gap between the underbody and the ground but also in the narrower gap between the side of the train and the tunnel wall gradually decreases from the head toward the tail of the train. In the same mechanism as the open air, a meandering airflow is generated throughout the side and underbody of the train and causes pressure fluctuations along the side of the train. Finally, it is demonstrated that the wavelength of pressure fluctuations along the side of the actual train can be estimated from the present LES results.

著者

酒井 宏樹 梶島 岳夫 太田 貴士

出版者

一般社団法人日本機械学会

雑誌

流体工学部門講演会講演論文集 (ISSN:13482882)

巻号頁・発行日

vol.2005, 2005-10-28

著者

梶島 岳夫

出版者

日本混相流学会

雑誌

混相流 (ISSN:09142843)

巻号頁・発行日

vol.31, no.2, pp.135-138, 2017-06-15 (Released:2017-07-18)

参考文献数

19

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The turbulence modulation, that means influences of dispersed particles to the fluid turbulence, is one of the challenging subjects in the multiphase flow research. In recent decades, experimental and numerical researches have been conducted extensively. Especially the direct numerical simulation (DNS) became a powerful means to reveal the multiphase turbulence phenomena. But DNS cannot become a practical tool for multiphase flows in industry or in nature. In this review article, an example of particle-laden flow by the immersed solid method and our recent progress for the application to the two-phase heat transfer are shown. Then, considering the current status, it is pointed out that some moderately-averaged equation, which includes momentum exchange and residual stress terms, is essential for semi-DNS including finite-sized particles (e.g., Kolmogorov scale particle) to deal with large-scale multiphase flow fields.

著者

佐藤 範和 竹内 伸太郎 梶島 岳夫 稲垣 昌英 堀之内 成明

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集B編 (ISSN:18848346)

巻号頁・発行日

vol.79, no.803, pp.1219-1231, 2013 (Released:2013-07-25)

参考文献数

13

被引用文献数

1 1

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A new discretization scheme of a Cartesian grid method for flow with heat transfer is proposed. The energy transport equation is discretized directly even in the boundary cells involving either the Dirichlet (isothermal) or the Neumann (iso-heat-flux/adiabatic) boundary conditions in order to ensure the energy conservation in those cells. The basic idea of this discretization is the same as the discretization scheme which is previously proposed by the present authors for boundary forcing in incompressible flow simulations. Moreover, the temperature gradients in both the normal and tangential directions at boundaries are required in the present method for representing the Neumann boundary condition on the Cartesian grids which do not necessarily coincide with the body geometries. The tangential components of the temperature gradients at boundaries are calculated by the extrapolations from the surrounding temperature field. Accuracy evaluations are conducted in a convective heat transfer problem in a flow between concentric cylindrical walls under the several different types of thermal boundary conditions applied at the inner and outer walls. It is confirmed that the present method significantly improves the accuracy orders for the temperature as well as the error magnitudes under both types of thermal boundary conditions. In particular, because the temperature gradients are correctly considered at the boundary cells where the Neumann boundary conditions are enforced, the same level of accuracy order is also maintained even in cases of non-uniformly distributed temperature at those boundaries.

著者

宮内 敏雄 三宅 裕 店橋 護 梶島 岳夫 笠木 伸英 宮内 敏雄

出版者

東京工業大学

雑誌

特定領域研究

巻号頁・発行日

2000

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乱流要素渦を理解し,それらを工学的に応用することを目的として,宮内は,種々の乱流場の直接数値計算結果から,要素渦の特性が乱流場の種類やレイノルズ数に依存しないこと,高レイノルズ数乱流中ではクラスターを形成することを明らかにした.また,要素渦による微細スケールでのスカラー輸送機構とフラクタル特性を明らかにした.三宅・辻本は,壁乱流の大規模な直接数値計算により,壁近傍場が遠方場とは独立に普遍的性質を持つこと,遠方場は大規模なストリーク構造で特徴づけられることを明らかにするとともに,スパン方向に狭隘な領域の数値実験では横渦しか存在し得ないことを示した.笠木は,壁乱流フィードバック制御システムの実現に向けて,DNSを用いて研究開発を行った.乱流制御のレイノルズ数効果の評価し,実際のアプリケーションにおいても制御効果がほとんど劣化せず,また,円管内乱流でも既存の制御アルゴリズムが有効であることを示し,現在の測定技術でも壁乱流制御が可能である制御アルゴリズムを開発した.また,せん断応力センサ群,壁面変形アクチュエータ群からなる制御システムのプロトタイプを試作・評価を行った.梶島・太田は添加物または壁面操作,圧力勾配などによって変調を受けた乱流場の渦構造を直接数値計算によって調べ,固体粒子群の分布や回転,壁面植毛の効果,空間発展乱流場(拡大・縮小流路)の影響を要素渦の視点から明らかにした.店橋は,高レイノルズ数一様等方性乱流の直接数値計算結果から乱流要素渦の階層構造及びスケール間のエネルギー輸送機構を明らかにするとともに,SGSモデルの評価を行った.