Wave Force Coefficients for Rough Vertical Cylinders

Wave forces on small sections of vertical tubes were measured in a wave tank test. The tube sizes and the wave parameters were such that both the inertia and the drag dominated areas were covered in the test. The surface of the tubes was sand-roughened to simulate the marine growth on these tubes. The hydrodynamic coefficients from these forces were computed with the help of the Morison equation. The roughnesses of the tubes were varied to show their effects on the inertia, drag, and lift coefficients. Mean values of these coefficients versus the Keulegan-Carpenter number were used to compute total forces on the tubes which were compared with the measured total forces. The drag and lift coefficients increased with the increased roughness of the tubes, while the inertia coefficients were relatively unaffected.