THE AERODYNAMIC DISTURBANCE CAUSED BY THE FREE-ENDS OF A CIRCULAR-CYLINDER IMMERSED IN A UNIFORM-FLOW

The disturbances caused by the free-ends of a smooth, circular cylinder immersed in a low-turbulence, steady, uniform flow have been determined. The cylinder was sufficiently long to include an undisturbed central section separating the two interference regions and was treated as two cantilevers springing from the plane of symmetry at the centre of the span. Measurements were made of mean and fluctuating surface pressures, local mean pressure drag, r.m.s. lift and r.m.s. drag and Strouhal number of vortex shedding, at an upper subcritical Reynolds number of 4.4 x 10(4). Oil-flow visualization was performed on the surface of the cylinder. The results reveal the nature of the disturbance to vortex shedding within the interference region, which was found to extend to a distance of 20 cylinder diameters from the free-end.