Local characteristics of bubbly flow in rods assembly 3 x 3

This study focuses on the experimental investigation of local characteristics of upward bubble flow in a 3 x 3 square rod bundle assembly. The experiments were conducted at Reynolds numbers ranging from 4000 to 11000 and gas void fractions up to 10%. The distribution of the gas phase around the central rod of the assembly was measured using a frontal conductivity probe, while the wall shear stress on the central rod was obtained through the electrodiffusion method. It is shown that the gas phase distribution does not exhibit the symmetry characteristic of the assembly cross-section. Furthermore, as the distance from the spacer grid increases, a reconfiguration of void fraction profiles is observed. This explains the non-monotonic dependence of wall shear stress and wall shear stress fluctuations on the distance to the spacer grid.