Structure of turbulent flow in subchannel of rod bundle downstream of spacer grid with flow mixing device

An experimental investigation and numerical study were performed to investigate the structure of the turbulent flow in the subchannel of a rod bundle downstream of the spacer grid with a flow-mixing device, the swirl vane. The time mean axial velocity, lateral velocity, and turbulent intensities in all directions were measured using air as the working fluid at a Reynolds number of 1.2x105 for two deflecting angles of the swirl vanes. The swirl with a 30deg vane was stronger than that with a 40deg vane along the diagonal of the subchannel. The axis of the swirling flow at the end of the test section was eccentric to the lower gap and the secondary flow was detected near the rod surface. The CFD (Computational Fluid Dynamics) predictions on the axial and lateral mean flow velocities in the subchannel were compared with the measurements. The predicted results of the axial and lateral velocity had a similar trend with the measured ones. (author)