Experimental study of gas entrainment phenomena; Developing process of surface vortex

Ezure, Toshiki ; Kimura, Nobuyuki; Hayashi, Kenji; Kamide, Hideki 

According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues for the latest fast reactor design. It is required to clarify the criterion of gas entrainment at free surface and the tolerance of gas entrainment. In the present study, some visualization experiments were performed in the water-air system focusing on the gas entrainment due to a surface vortex. The gas entrainment occurs intermittently and the vortex develops and decays in time. Then developing process of the vortex is significant to estimate the gas entrainment phenomena. Multi plane PIV using a scanning mirror was adopted to investigate the temporal and spatial development of velocity around the vortex. The spatial propagation of downward velocity was clarified as the key factors of the vortex development.