Flow past short circular cylinders with two free ends

Preliminary tests have been carried out on short circular cylinders with both ends free. Drag force is measured across the range 6 × 10 4 < Re < 2.6 × 10 5 for cylinders of length to diameter ratio L / D between 1 and 10. The effect of hemispherical ends is also investigated. A kind of periodic vortex shedding is found in the range 2 < L / D < 8. The oil-film surface flow visualization shows that the ‘eyes’ near the free ends (regions of low pressure) gradually disappear as L / D is reduced to 3. An asymmetric flow pattern is established for very short cylinders ( L / D < 3). The detailed measurements of pressure distribution along and across models shows asymmetries of minimum and base pressures along the span. The asymmetric flow produces yawing and rolling moments which are also measured.