Transverse forces on rough cylinders in harmonic flow

Abstract

The transverse forces acting on smooth and sand-roughened circular cylinders immersed in an harmonically oscillating flow have been measured using a recently constructed U-shaped water tunnel. The lift coefficients were found to depend on Keulegan-Carpenter number but independent of the Reynolds number within the range of relative roughness and Reynolds numbers tested. The results have shown that the lift coefficients for smooth cylinders at low Reynolds numbers are nearly identical with those obtained for rough cylinders at very high Reynolds numbers at the corresponding amplitude ratios. The results have also shown that the transverse force is a significant fraction of he in-line force and must be taken into consideration in the design of structures.