Turbulent flow in a ribbed channel: Flow structures in the vicinity of a rib

PIV measurements are performed in a channel with periodic ribs on one wall. The emphasis of this study is to investigate the flow
structures in the vicinity of a rib in terms of mean velocities, Reynolds stresses, probability density functions (PDF), and two-point
correlations. The PDF distribution of u0 is bimodal in the separated shear layer downstream of the rib. The maximum Reynolds
shear stresses occur at the leading edge of the rib. Based on quadrant analysis, it is found that ejection motions make a dominant
contribution to the Reynolds shear stress in this region. Moreover, topology-based visualization is applied to the separation bubble
upstream of the rib. Salient critical points and limit cycles are extracted, which gives clues to the physical processes occurring in
the flow.