著者

森西 洋平

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.62, no.604, pp.4098-4105, 1996-12-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

12 10

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In this report, finite difference schemes in staggered and collocated grid systems are considered in light of the analytical requirements that were discussed in the first report. The standard second-order accurate finite difference scheme with divergence form in a staggered grid system is proper. Proper second-order accurate advective and skew-symmetric forms have been proposed in the staggered grid system. Existing fourth-order accurate convective schemes in a staggered grid system are not proper. Proper higher-order accurate finite difference schemes in a staggered grid system are proposed. This is novel because higher-order staggered grid schemes that conserve momentum and kinetic energy simultaneously do not previously appear in the literature. The pressure term is not conservative in the kinetic energy equation in the collocated grid system, although we can construct proper-second and fourth-order accurate convective schemes in this system.

著者

森西 洋平

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.65, no.630, pp.505-512, 1999-02-25 (Released:2008-03-28)

参考文献数

18

被引用文献数

2 3

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Finite difference method in a collocated grid system has the merits of both regular and staggered grid systems, and has mainly been used for steady flow simulations. Recently, some unsteady flows have been simulated by using the collocated grid system. The author pointed out a violation of kinetic energy conservation in the collocated grid system, which is important to unsteady turbulent flow simulations. In this paper, a modified algorithm for improving the conservation property of the collcated grid system is proposed. Van Kan type pressure correction is introduced to minimize the defect. The modified algorithm with fourth order accuracy in space is also proposed. Conservation properties of the numerical algorithms in the collocated grid system are demonstrated on the example of two dimensional periodic inviscid flow simulations. Plane turbulent channel flow simulations are also performed to confirm the reliavility of the modified algorithm.

著者

森西 洋平 福井 岳人

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.75, no.759, pp.2163-2172, 2009

参考文献数

19

被引用文献数

2

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A non-segregated numerical algorithm is proposed for unsteady incompressible flow simulations with the fully discrete fully conservative finite difference scheme. The fully conservative finite difference scheme is useful for the numerical simulations of unsteady turbulent flow because of its stability and reliability. However, a large system of nonlinear discrete equations should be solved for the fully (spatio-temporal) discrete fully conservative scheme. In this study, the Jacobian-Free Newton-Krylov (JFNK) method with the GMRES(m) method as a Krylov iterative solver is introduced as a non-linear solver in the non-segregated numerical algorithm. A couple of preconditionings to the Krylov iterative method are tested and a new effective physical-based preconditioning is proposed. Numerical tests on the DNS of turbulent channel flow demonstrate the availability of the present method. Then, the DNS of backward facing step flow is carried out for an example of a stiff problem in which the streamwise grid spacings are locally fine.

著者

吉住 文太 近藤 靖裕 諸井 隆宏 玉野 真司 森西 洋平

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.806, pp.2003-2018, 2013 (Released:2013-10-25)

参考文献数

3

被引用文献数

2 2

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The opening delay of a discharge reed valve for compressors caused by the oil film in the clearance between the reed and the valve seat is investigated. The developed simulation method which couples the reed deformation, the gas flow and the oil film flow is applied to simulate delay times on two types of seats with different contact areas. Three models for cavitaion in the oil film are tested; no-cavitation model, the static cavitation model (Reynolds' condition), and the dynamic cavitaton model in which the bubble expansion is directly simulated. The calculaion through the dynamic cavitation model reproduces well experimental results with regard to the delay time and oil film behaviors of cavitation and blow-by (oil film rupture). The result also shows that the growth of cavitation bubbles occupies the change in the oil film volume and prevents the oil film pressure from falling. The rupture mechanism based on the calculation results is that the increase of the oil film thickness directly causes the oil film pressure recovery leading to the blow-by flow, and both cavitation and the smaller contact area promote the growth of the oil film thickness.

著者

森西 洋平

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.62, no.604, pp.4106-4112, 1996-12-25 (Released:2008-03-28)

参考文献数

14

被引用文献数

4 5

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In this report, numerical tests of the conservation properties of finite difference schemes are performed. Inviscid flow simulations in a two-dimensional periodic domain are performed using several finite difference schemes that are discussed in the first and second reports. The momentum and kinetic energy are conserved when the proper schemes in regular and staggered grid systems are used. The defect of the finite difference schemes in a collocated grid system is emphasized in the simulation. In addition, plane channel flows at Re=180 and 2000 are simulated using the proper fourth-order accurate finite difference scheme in a staggered grid system and the results are better than those of the second-order accurate algorithm and an existing fourth-order accurate scheme.

著者

森西 洋平

出版者

社団法人 日本流体力学会

雑誌

日本流体力学会誌「ながれ」 (ISSN:02863154)

巻号頁・発行日

vol.19, no.3, pp.164-170, 2000-06-30 (Released:2011-03-07)

参考文献数

12

被引用文献数

1

著者

何 永森 森西 洋平 小林 敏雄

出版者

東京大学生産技術研究所

雑誌

生産研究 (ISSN:0037105X)

巻号頁・発行日

vol.40, no.1, pp.p39-42, 1988-01

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特集 乱流の数値シミュレーション(NST) その4

著者

森西 洋平 小林 敏雄

出版者

東京大学生産技術研究所

雑誌

生産研究 (ISSN:0037105X)

巻号頁・発行日

vol.43, no.1, pp.4-11, 1991-01-01

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特集 乱流の数値シミュレーション(NST) その7