Boundary Layer Characterization during Impulsive Spin-up and Spin-down Motions of High-Reynolds Number Rotating Flow

International audienceVarious planar and stereo PIV measurements have been conducted for high-Re in a rotating tank during spin-up and spin-down with the purpose to characterize the side-wall boundary-layer development and corresponding vorticity distributions. The effect of Ekman pumping was successfully suppressed with an additional saltwater layer. An algorithm was developed to identify distinct patterns such as Görtler vortices and transition. Despite a linearly stable character, the spin-up showed transition turbulent for high Reynolds numbers. It is hypothesized that shear-layer instabilities trigger the transition process for high velocities combined with extremely small wall curvature