Experimental Study of Flow Field and Transition Characteristics in Rod Bundle Channel

Based on particle image velocimetry technique, the 22 cases fully developed flow field, and turbulence statistics in the 5×5 rod bundle were studied in the range of Reynolds number from 310 to 12296. For the full field and instantaneous velocity vector obtained by PIV measurement, time-averaged, statistical, spectral are used to investigate the velocity distribution, turbulence characteristics, and spectral characteristics in different subchannel under different Reynold number.There is the low Reynolds number effect in the rod bundle channel, and the dimensionless RMS velocity decreases with the increase of Reynolds number. When reach transition Reynolds number, the area-averaged dimensionless RMS suddenly rises. By studying the turbulence intensity variation at different positions in the rod bundle, it can be seen that the transition Reynolds numbers at different positions in the subchannel are different. Finally, the experimental data can be used to verify the applicability of the turbulence model to different Reynolds Numbers