Basic study on flow separation phenomenon at the elbow in a large-diameter pipe; Research report in FY2007

Iwamoto, Yukiharu*; Sogo, Motosuke*; Aizawa, Kosuke ; Nakanishi, Shigeyuki*; Yamano, Hidemasa   

Experimental studies of the 1/10-scale model of a hot leg piping and their numerical analyses were carried out in order to guarantee the designing of the sodium-cooled fast breeder reactor. The structure of the flow fluctuation was clarified by means of pressure measurements, laser doppler velocimetry (LDV) and flow visualization. LDV measurements were examined for Reynolds number of 50000. FFT analyses of axial velocities indicate that two kinds of flow fluctuations exist in the present elbow. One is the fluctuation with approximate Strouhal number of 1.0 (3.2 Hz) occurring in a shear flow region. The other is with approximate Strouhal number of 0.5 (1.6 Hz) occurring in the separated and its downstream regions. These fluctuations were also observed by flow visualization. The analyses showed that the stream regime was in good agreement with visualization test results.