PIV Measurements of Lateral Flow on Fuel Subchannel

There have been many experimental attempts to measure the flow structures in a rod bundle array. In the early stage during two decades from 1970, fundamental studies on the flow mixing in a bare rod bundle have been frequently performed. Rehme has been measured the axial velocities and the shear stresses in a four rod bundle array by using the Pitot tube and the hot wire anemometry. Neti et al. performed the LDV measurements for a 3x3 rod array and presented the lateral fluctuations were about 1% magnitudes of the axial flow. From the beginning of eighty, the effect of the vaned spacer grid on thermal hydraulic behavior in a rod bundle array was widely studied as being required the better performance of the heat transfer in a nuclear reactor. Yao et al. have suggested the predictive formulation of the heat transfer by analyzing the physical mechanism and compared with experimental data. Yang et al. have performed the experiments for the measurement of the axial and lateral velocities and their turbulence intensities in a 6x6 rod bundle array with different spacer grids. Some useful knowledge and insight of the thermal hydraulic behavior in a rod bundle array was obtained from the above extensive experimental works. However, the data resolution in a subchannel is insufficient to get the information of the channel-wise detailed flow structure. Moreover, precise experimental data in a rod array with various flow promoters is increasingly required from the workers in the field of CFD (Computational Fluid Dynamics)