Periodic large scale vortex structure in rectangular channels with non-uniform wall roughness

The periodic large scale vortex structure is highly accounted for the local flow and heat transfer and turbulent mixing in rod bundles. In this paper, the mechanism of the periodic large scale structures is studied in terms of the vortex dynamics. The vortex structure in rectangular channels with different inlet velocities is also analyzed. It is found that the periodic large scale vortex structure exists in the rectangular channels with transverse vorticity gradient. The distribution of vorticity is strictly related with that of vortex structure.