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Applications of Very Large Scale Fluid-Flow Computations to Industrial Problems
Chisachi Kato 한국전산유체공학회 2017 한국전산유체공학회 학술대회논문집 Vol.2017 No.11
Fluid-flow computations that use several tens billion grids has already become feasible and the maximum number of the computational grids is expected to reach a trillion even for industrial applications in 2020. We have demonstrated that wall-resolved LES (WR-LES), where all the active turbulent eddies are directly computed by the numerical grids, can become a very-powerful engineering tool, and that they do have a potential to completely replace experiments. In this article, we will give a brief overview of the software that is capable of performing such a large-scale computation and will show some latest results of applications of WR-LES in automobile and shipbuilding industries.
Taku Iwase,Hideshi Obara,Yoshinobu Yamade,Chisachi Kato 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1
In this study we calculated flow fields and aerodynamic noise in centrifugal fan of air conditioner by large eddy simulation (LES). The numerical simulation code employed throughout the LES was FrontFlow/blue (FFB). We compared calculation results for 10 million grids (10M-grid), 60 million grids (60M-grid) and 500 million grids (500M-grid) to investigate the influence of grid resolution on the prediction accuracy. The prediction accuracy of the aerodynamic noise by the 500M-grid was improved compared to the 10M-grid and 60M-grid calculation results. The grid resolutions between the shroud and the bell mouth and between one blade and an adjacent blade were important. Moreover, we found the proper capturing of the streaks contributed to better prediction.
Large Eddy Simulation of the Dynamic Response of an Inducer to Flow Rate Fluctuations
Kang, Dong-Hyuk,Yonezawa, Koichi,Ueda, Tatsuya,Yamanishi, Nobuhiro,Kato, Chisachi,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.4
A Large Eddy Simulation (LES) of the flow in an inducer is carried out under flow rate oscillations. The present study focuses on the dynamic response of the backflow and the unsteady pressure performance to the flow rate fluctuations under non-cavitation conditions. The amplitude of angular momentum fluctuation evaluated by LES is larger than that evaluated by RANS. However, the phase delay of backflow is nearly the same as RANS calculation. The pressure performance curve exhibits a closed curve caused by the inertia effect associated with the flow rate fluctuations. Compared with simplified one dimensional evaluation of the inertia component, the component obtained by LES is smaller. The negative slope of averaged performance curve becomes larger under unsteady conditions. From the conservations of angular momentum and energy, an expression useful for the evaluation of unsteady pressure rise was obtained. The examination of each term of this expression show that the apparent decrease of inertia effects is caused by the response delay of Euler's head and that the increase of negative slope is caused by the delay of inertial term associated with the delay of backflow response. These results are qualitatively confirmed by experiments.