Tests were conducted to evaluate the tip effects on the local air loads that act on a circular cylinder normal to a flow at Reynolds numbers, based on cylinder diameter, of 0.38 x 106, 0.53 x 106, 0.65 x 106 and 0.75 x 106 (corresponding to wind tunnel dynamic pressures of 10, 20, 30, and 40 psf, respectively). Tip configurations consisted of a blunt-end (or smokestack), a hemisphere, a 15 degree half-angle cone, and an ellipsoid with semi-major axis of 1.5 cylinder diameters. Localized boundary layer tripping facilitated controlled disturbances near the tip.
Unsteady lift and drag were significantly altered by the hemispherical and ellipsoidal ends as compared with the blunt-end. In contrast, the conical tip showed much smaller changes. Local lift and drag coefficients, as well as cross-correlation coefficients, vary rapidly along the cylinder axis near the tip.
The importance of boundary layer characteristics on the fluctuating forces was demonstrated by boundary layer tripping with air blowing out through suitably located orifices in the cylinder.
