MEAN FLOW GENERATION DUE TO LONGITUDINAL LIBRATIONS OF SIDE-WALLS OF A ROTATING ANNULUS

etc15 Tracking Number 175

Laboratory experiments with rotating annuli are reported that reveal a prograde jet, which is adjacent either to a (longitudinally) librating inner straight cylinder or to a librating inner truncated cone (frustum), whereas the outer cylindrical wall and bottom and top lids rotate with constant angular velocity. In the frustum case, the jet is located on a straight cylindrical surface which is circumscribed about the frustum and joins the bottom lid. These findings are supported by direct numerical simulations which show good agreement between experimental data and numerical results and, when the centrifugal instability of the Stokes boundary layer near the oscillating sidewall does not set in, highlight the important role of local dynamical processes in the corners, between the inner cylinder and the lids, in producing the prograde jet.