著者

山崎 諒 河内 俊憲 永田 靖典 柳瀬 眞一郎

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.83, no.853, pp.17-00181, 2017 (Released:2017-09-25)

参考文献数

30

被引用文献数

2 2

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Numerical prediction of air-entraining and submerged vortices in pump sumps is important for engineering applications. The validation of pump sump simulations, however, still is not enough, because the simulations is very complicated; for examples, treatment of gas-liquid interface, detection method of the vortices and selection of turbulence model etc. We conducted numerical simulations of the benchmark experiments of the pump sump conducted by Matsui et al. (2006, 2016) and compared the simulation with the experimental data to investigate the effects of turbulence model, grid density and detection method of the vortices. We determined a threshold of the gas-liquid fraction function of VOF method (α) and the second invariant of velocity gradient tensor (Q2) to detect the air-entraining and submerged vortices by using vorticity, respectively. This method well detected the vortices and well reproduced the experiments for the RANS simulation using SST k-ω model. Large eddy simulation using Smagorinsky model, however, was sensitive to the grid system and difficult to reproduce the experimental vortex structures even for the finest grid system having 3.7 million cells.

著者

河内 俊憲 三谷 徹 平岩 徹夫 富岡 定毅 升谷 五郎

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 (ISSN:13446460)

巻号頁・発行日

vol.51, no.595, pp.403-411, 2003 (Released:2003-09-26)

参考文献数

15

被引用文献数

2 6

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A one-dimensional theoretical method for an evaluation of the net thrust of a scramjet engine is presented. To calculate the thrust performance of the engine analytically, an efficiency characterizing compression process, such as recovery factor in total pressure or kinetic energy efficiency etc., is necessary. In the previous theoretical method, this efficiency was roughly assumed. Although the effect of aerodynamic parameters and configuration parameters on the thrust can be investigated with this rough assumption, the net thrust evaluated with this method was not enough accurate to be compared with the measured thrust in experiments. The total pressure loss is chosen as the efficiency in this paper. This total pressure loss is evaluated from the engine internal drag with the wind tunnel experiment, which is due to irreversible process through the engines. The theoretical maximum thrust of the engines can be calculated with this new method.

著者

永田 靖典 石原 遼一 前田 真吾 河内 俊憲 柳瀬 眞一郎

出版者

一般社団法人 日本航空宇宙学会

雑誌

日本航空宇宙学会論文集 (ISSN:13446460)

巻号頁・発行日

vol.67, no.1, pp.16-24, 2019 (Released:2019-02-05)

参考文献数

14

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The electrodynamic heat shield is new type of heat protection system for atmospheric-entry vehicle, which utilizes the Lorentz force acting on the weakly ionized plasma flow inside the shock layer. A huge amount of calculation is necessary to estimate overall effect of the electrodynamic heat shield, because its effect interacts with the atmospheric-entry trajectory. In the present study, the Viscous Shock Layer (VSL) analysis method for electrodynamic heat shield is proposed for the quick analysis, which can calculate much faster than Navier-Stokes (NS) simulation. For this purpose, the VSL equations for the electrodynamic heat shield analysis are introduced under the ideal gas assumption, including circumferential momentum equation and Maxwell equations. The new method is also proposed to solve the new VSL equations. By the comparison to the NS simulation, the new VSL method gives good estimations of drag force and wall heat flux for wide ranges of interaction parameter and Hall parameter although the slight difference of wall heat flux at the stagnation point is observed. Therefore, the present VSL method could be applicable to the estimation tool of the electrodynamic heat shield effect.