Oscillating flow over a cylinder at large Reynolds number

The boundary-layer flow over a circular cylinder at a Reynolds number of 1·06 × 105 has been studied both experimentally and theoretically. The investigation was designed to concentrate on the self-induced oscillations occurring in the flow; at this Reynolds number, these oscillations have generally been ignored heretofore. In the experimental part of the investigation both the inviscid flow and boundary-layer flow reversals were measured as functions of time. The theoretical part of the study started with the measured inviscid flow and calculated all the boundary-layer characteristics. The boundary-layer calculations themselves revealed some very interesting fine-scale structure of the flow, which strongly indicated that the vanishing of wall shear does not signal the onset of separation for unsteady flow. In general, the agreement between the theoretical calculations and the experimental results was excellent and the unsteady component of this supposedly steady flow was found to be very significant.