Evaluation of flow-induced vibration of a primary circuit hot-leg piping in a sodium-cooled fast reactor, 4; LDV flow measurement in a 1/10-scale hot-log piping test facility

Iwamoto, Yukiharu*; Ogawa, Shota*; Yasuda, Kazunori*; Sogo, Motosuke*; Tanaka, Masaaki  ; Yamano, Hidemasa   

LDV measurements in a 90 elbow which curvature radius coincides with the diameter have been examined for a deflected inflow that became faster inside. Compared to a case of a 4.9D pipe, the deflected inflow reinforced a convex velocity distribution near the curvature in the downstream region. This concludes the deflected inflow promotes the secondary flow of Prandtl's first kind. Frequency analyses of axial flow fluctuations show the dominant frequency can be seen in the downstream even when deflected. But its Strouhal number increases to 0.6 from 0.5 compared to the short one. Results of frequency analyses are also shown for an inflow from a 10D pipe and a swirl generator. Dominant Strouhal numbers mostly become 0.5 except for 0.6 in cases of the inflow from the 10D pipe and deflector. This frequency shift might be related with the boundary layer size and the local flow velocity since the corresponding fluctuation is caused by vortex from the boundary layer at the elbow.