Transient behavior of gas entrainment caused by surface vortex

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

A compact sodium cooled reactor is one of important candidates as FBRs and has been investigated in the feasibility study of FBR cycle. According to the compact sizing of reactor vessel, gas entrainment at the free surface of sodium coolant becomes one of the significant issues for reactor design, and it is required to clarify the criterion of gas entrainment at free surface and the tolerance. In the present study, some visualization experiments were performed in a water-air system focusing on the gas entrainment due to surface vortex and its transient phenomena. Influences of horizontal velocity were clarified by the visualization. Time trends of circulation and length of gas core for the intermittent surface vortices were measured by the particle image velocimetry and visualization. It was found that the gas core length extends with time delay to the increase of circulation around the vortex.