Aerodynamic investigation of a rotating rib-roughened channel by time-resolved particle image velocimetry

Abstract

Particle image velocimetry (PIV) is used to study the turbulent flow over the rib-roughened wall of a cooling channel model in rotation. The aspect ratio is 0.9, the blockage ratio is 0.1 and the rib pitch-to-height ratio is 10. The flow direction is outward, with a Reynolds number of 1.5 × 104 and a rotation number of 0.3 in both rotational directions. The PIV system rotates with the channel, allowing to directly measure the relative flow velocity with high spatial and temporal resolution. Coriolis forces affect the stability of the shear layers: cyclonic (anticyclonic) rotation inhibits (enhances) the turbulent motion, influencing velocity, vorticity, and turbulence intensity of the flow. The time-resolved measurements show the effect of rotation on the shear layer instability and on the consequent formation of spanwise vortices, as well as on the time trace of the reattachment point. Turbulent energy spectra suggest that all temporal scales are affected by rotation.