Matched refractive-index PIV visualization of complex flow structure in a three-dimentionally connected dual elbow

三次元的に接続された2段エルボにおける複雑流動構造の屈折率調合PIVによる可視化

結城 和久*; 長谷川 駿介*; 佐藤 司*; 橋爪 秀利*; 相澤 康介 ; 山野 秀将   

Yuki, Kazuhisa*; Hasegawa, Shunsuke*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Aizawa, Kosuke; Yamano, Hidemasa

Flow structure in a three-dimensionally connected dual elbow is visualized simulating the 1st and 2nd elbows of JSFR cold-leg piping. A matched refractive-index PIV measurement clarifies that a low-velocity region formed on the inner wall side of the 1st elbow develops toward the 2nd elbow. The velocity recovery region reaches the 2nd elbow, the geometry of the 2nd elbow has a significant impact on the characteristics of the vortex shedding in the velocity recovery region. Contrary, flow separation is inconclusive in the 2nd elbow, whereas high-velocity flow with intense velocity fluctuation is confirmed on the inner wall side. Furthermore, the unsteady vortices shed from the velocity recovery region are transferred to the central area of the 2nd elbow while growing significantly. This study shows a strong swirling flow is formed in the 2nd elbow. These flow structures are due to the distorted 1st elbow flow and the 2nd elbow shape effect.