Experimental and numerical study on density stratification erosion phenomena with a vertical buoyant jet in a small vessel

鉛直噴流による小型容器内密度成層侵食に関する実験および数値解析的研究

安部 諭  ; 石垣 将宏 ; 柴本 泰照 ; 与能本 泰介 

Abe, Satoshi; Ishigaki, Masahiro; Shibamoto, Yasuteru; Yonomoto, Taisuke

The Japan Atomic Energy Agency has started the ROSA-SA project to investigate thermal hydraulic phenomena in a reactor containment vessel during a severe accident. The hydrogen distribution in the vessel is one of significant safety issues in discussing a potential of hydrogen combustion in the containment. This paper focuses on a density stratification erosion and break-up mechanism with a vertical buoyant jet promoting the turbulent helium transport. Small scale experiment and computational fluid dynamics (CFD) analyses were carried out for investigating this phenomena. In the experiment, a rectangular vessel made with acrylic plates with a width of 1.5m, a length of 1.5 m and a height of 1.8 m was used for visualizing flow field with particle image velocimetry system. The quadrupole mass spectrometer system with a multiport rotating valve was applied for measuring gaseous concentration at 20 elevation points. In CFD analysis with OpenFOAM, two typical well-used turbulence models were used: low-Reynolds number type k- model and SST k- model, with a turbulence model modification to consider the buoyant effect in the stratification. As a result, the stratification erosion in the CFD analyses with the modified turbulence model agreed well with the experimental data, indicating importance of the turbulence damping by the buoyant effect.