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

よどみ部と周辺流れの間に発生する自由表面渦ガス巻込みに関する実験研究

江連 俊樹 ; 伊藤 啓; 田中 正暁  ; 大島 宏之; 亀山 祐理*

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

ナトリウム冷却高速炉設計の重要課題である液面からのカバーガス巻込みについて、よどみ部と周辺流れの間に発生する自由表面渦ガス巻込みに関する実験研究を行った。水平および吸込み流速を数条件変化させ、自由液面の可視化と粒子画像流速計測適用することで自由液面部くぼみ形状と渦廻りの流速分布をそれぞれ同時に計測した。実験で得られた液面形状および速度分布より、ガス巻込み渦に関する循環、鉛直報告速度勾配およびくぼみ形状それぞれの時間発達の関係をガス巻込み評価手法整備用の基礎実験データとして定量把握した。さらに、渦モデルに基づくガス巻込み評価の有効性を確認した。

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.