Basic study on flow separation phenomenon in cooling system piping in fast reactors; Clarification of complex flow structure in a multi-elbow in a high Reynolds number regime (Joint research report in JFY2008 and JFY2009)

Ebara, Shinji*; Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Aizawa, Kosuke ; Yamano, Hidemasa   

In Tohoku University, different scale model experiments were carried out in order to clarify unsteady flow fields and pressure fluctuation characteristics in the cold leg piping by means of visualization experiment and pressure measurement, respectively, and to investigate the scale effect. In JFY2008, the visualization experiment by PIV measurement for the 1/15 scale piping was carried out using a double elbow geometry. Besides, shakedown tests of the 1/7 scale model were conducted for the case of a single elbow. In JFY2009, visualization experiments for the 1/7 scale models with the single and a three-dimensionally connected double elbow geometries were carried out. From these obtained data, effects of the multiple elbows on the flow field were assessed. In addition, the pressure measurements for single elbow flows by using 1/15 and 1/7 scale models were performed. In JAEA, numerical analyses for the 1/7 scale double elbow experiments were performed using the commercial thermal-hydraulics code STAR-CD. The analyses showed that the calculated velocity distributions were in good agreement with the visualization experimental results. It was confirmed, from these analyses, that the URANS analysis method validated for the single elbow flow has applicability to the double elbow flow.