Flow-induced Vibration Tests of Large Diameter and High Velocity Piping (2) Flow Pattern and Pressure Fluctuation Behaviors of Elbow

Fujii, Tadashi; Chikazawa, Yoshitaka  ; Konomura, Mamoru

A conceptual design study of the sodium-cooled fast reactor (JSFR) is in progress in the Feasibility Study on Commercialized Fast Reactor Cycle Systems (F/S). The cooling system of the reactor is composed of two loops in order to reduce construction cost. According to reduction of loop number, large diameter pipings are adopted in the primary cooling system (for example, outer diameter of a hot leg piping is 1.27m). And the mean velocity in the piping increases to 9 m/s level. Then, flow visualization and flow-induced vibration tests using 1/3 scale water test facility, which simulates a hot leg piping, have been started in order to confirm the realization of the piping design for primary cooling system. As a first step of the test series, flow visualization test was conducted using acryl model piping, following results are obtained. (1)Flow pattern and velocity distributions in the model piping are independent of Reynolds number. The maximum velocity in the elbow is about 1.5 times of the mean velocity. (2)Total pressure loss coefficients of the elbow under high Reynolds number conditions (up to 3.3106), which are exceeded from past test condition, are about 1.3. According to this, the turbulence energy given from flow separation of the elbow is small. (3)As for pressure fluctuation behaviors, pressure fluctuations of the region of flow separation are dominance in the model piping. An eminent peak in the power spectrum densities of pressure fluctuations at the border of region of flow separation is revealed at 0.45 of Strouhal number. (4)According to extent of the turbulence caused by flow separation of the elbow, the power spectrum densities of pressure fluctuations and the correlation lengths, which are applied in random vibration response evaluation for actual plant pipings, are classified into some sections.