Experiments on gas entrainment phenomena due to free surface vortex induced by flow passing beside stagnation region

Ezure, Toshiki ; Ito, Kei; Tanaka, Masaaki  ; Ohshima, Hiroyuki; Kameyama, Yuri*

In the design of sodium cooled fast reactors, cover gas entrainment into sodium coolant (gas entrainment) is one of significant thermal hydraulic issues. This paper describes experimental results on surface vortex type gas entrainment which occurs in a share flow area where flow passes beside the stagnation region. In the experiment, the relationship between the free surface dimple shape and the velocity distribution around the free surface vortex was simultaneously grasped under several horizontal and suction velocity conditions by means of visualization measurement and Particle Image Velocimetry measurement. As the results, quantitative relationships among circulation, vertical velocity gradient and the gas core length were obtained in time-trends as fundamental data to develop the evaluation method of gas entrainment. Furthermore, it was confirmed that the evaluation method based on a vortex model, was an effective way to evaluate gas entrainment.