Unsteady hydraulic characteristics in large-diameter pipings with elbow for JSFR, 4; Influence of elbow curvature on velocity fluctuation at elbow outlet

Ono, Ayako ; Kimura, Nobuyuki; Kamide, Hideki ; Tobita, Akira

The main cooling system of Japan Sodium-Cooled Fast Reactor (JSFR) consists of two loops to reduce the plant construction cost. In the design of JSFR, sodium coolant velocity is beyond 9 m/s in the primary hot leg pipe having a short elbow with large-diameter. Under such a system condition in the cooling system, the flow-induced vibration (FIV) is concerned. The evaluation of the structural integrity of pipings in JSFR will need to grasp the mechanism of FIV at the elbow. In this study, two types of 1/8 scaled elbows with different curvature ratio were used to investigate the influence of curvature on velocity fluctuation. The velocity fields in the elbows were measured using a high speed PIV method. Unsteady behavior of secondary flow and separation flow in the elbow were observed in the two types of elbows. It was found that the growth of secondary flow correlated with the flow fluctuation near the inside wall of the elbow.