Particle image velocimetry measurements of turbulent flows in rotating square ribbed ducts

This paper investigates the flow characteristics along a ribbed square duct using time-resolved particle image velocimetry. The Reynolds number, defined by the main flow velocity (1.82 m/s) and the hydraulic diameter (80 mm), is 10 000. The rotation numbers are 0, 0.13, 0.26, 0.39, and 0.52. The blockage and aspect ratios of the ribbed square duct are 0.1 and 1, respectively. As the rotation number increases, the recirculation zone on the suction side becomes larger, and the reattachment point moves downstream. The opposite behavior is observed on the pressure side, and this trend develops along the duct. Furthermore, the flow characteristics between different pairs of ribs along the duct vary greatly at the same rotation number. For the downstream ribs, the main stream velocity pattern is deflected more to the pressure side, where both the recirculation zone and the extreme region of Reynolds shear stress are larger than on the suction side.