Abstract
Unsteady boundary-layer and surface pressure measurements were made on a circular cylinder with timevarying blowing applied from a narrow spanwise slot. The effects of mean blowing level, blowing frequency, and boundary-layer trip location were examined at a Reynolds number of 2.2 X 105 based on cylinder diameter. Timeresolved pressures were recorded using pressure sensors located on the Coanda surface and around the circumference of the cylinder. Flush-mounted hot film probes were positioned both upstream and downstream of the slot to provide a qualitative measurement of the boundary-layer characteristics. The results have shown that the shear stress just downstream of the slot was always in-phase with the plenum pressure. However, increasing reduced frequency generally resulted in increasingly larger phase lags between the application of blowing and the development of the flow over the remainder of the Coanda surface. For both steady and unsteady blowing, the jet entrained the outer flow at the slot and remained attached to the Coanda surface, provided a fully attached laminar or turbulent boundary layer was obtained just prior to reaching the slot.
Published Version
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