OpenFOAMによる移動格子を用いたスロッシング解析の精度検証
スロッシング解析を実施する場合，流体に地震の加速度を与える方法が一般的である。しかしこの手法では，構造物に地震の変位を与えず，実現象とは異なる条件のため，構造物の条件等により解析に不具合が生じる可能性がある。そこで，近年導入された移動格子を使用し，矩形水槽を対象に構造物自体を振動させたスロッシング解析を行い，水面変動および圧力分布の精度を理論式及び既往の数値解析結果と比較，検証した。その結果，理論式，既往解析とも概ね一致し，変位入力による解析手法の精度は十分あることが確認された。さらに，水位変動及び壁面に作用する動水圧を対象として，加速度入力および変位入力による解析結果の違いについても検証した。その結果，両者の手法間で水位の解析結果に大きな違いはないものの，圧力については変位入力の場合に過小評価となる可能性があることが確認された。
キーワード：スロッシング現象，OpenFOAM，数値解析，動水圧，地震動，STAR-CD
＊１ 技術センター 社会基盤技術研究部 水理研究室
Verification of Sloshing Simulation Using Moving Mesh with OpenFOAM
When analyzing sloshing problems in CFD simulation, the seismic acceleration is generally applied as the acceleration acting on the fluid. However, in this calculation method, since seismic displacement is not applied to the tank itself, the conditions differ from the actual phenomena, and some problems in the simulation may be caused depending on the conditions of the analyzed structure. In this study, sloshing simulation of a rectangular tank was performed using OpenFOAM, an open source CFD code. OpenFOAM has been recently improved to implement a moving mesh, which enables the tank itself to be directly oscillated in sloshing analysis. The calculation results using a moving mesh were compared with theoretical equations and previous numerical calculation results to verify the changes in water level and the accuracy of the pressure distribution acting on the tank wall. It was found that the results were generally in good agreement with the theoretical equations and past analysis, so it was concluded that the analysis method in which the displacements were input has sufficient accuracy. Moreover, the differences in analysis results between the acceleration input method and the displacement input method were verified for the variation in water level and the hydrodynamic pressure acting on the tank wall surfaces. From the results it was found that although there was no major difference in the analysis results for water level between the two methods, it was confirmed that for the pressure results, the displacement input method may underestimate the pressure.
Keywords: sloshing phenomena, OpenFOAM, numerical simulation, hydrodynamic pressure, seismic motions, STAR-CD
*1 Hydraulic Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology