B223 ロッドバンドル内液流の乱流特性(OS9 熱・流動)

Abstract

Validation of turbulence models is not an easy task mainly due to lack of experimental data on turbulent flows in rod bundles. In this study, we therefore measured distributions of velocity and turbulence intensities of water flow in a 2x2 rod bundle by using a stereoscopic PIV system. The diameter and pitch of the rods were 20 and 25 mm, respectively. Area-averaged velocity was 2 m/s. Local time-averaged velocity and turbulent intensities were obtained from 10,000 instantaneous velocities at each measurement point. Experimental results showed that horizontal components of turbulence intensity in the cross-section are anisotropic near the rod gap. Since eddies larger than the gap width cannot exist in the rod gap, the turbulence spectrum takes low values in the rod gap compared with center region of subchannel. To the contrary, difference in the turbulence spectrum of eddies smaller than the gap width is small between the rod gap and the center of subchannel.