LARGE-SCALE HORIZONTAL CYLINDER FORCES IN WAVES AND CURRENTS

This paper describes laboratory measurements of forces and pressures o n smooth and rough horizontal cylinders of diameters 0.21m and 0.5m be neath waves of heights up to 1.9m, in the presence of currents up to 1 m/s in either direction. Drag and inertia coefficients evaluated on a wave-by-wave basis exhibited very wide scatter, but average values ove r all Keulegan Carpenter numbers were found insensitive to currents an d gave predictions of the largest peak horizontal forces to within 16% of the measurements in 90% of cases in irregular waves. Vertical forc es deviated much more strongly from Morison predictions owing to vorte x shedding, and to slowly-varying forces due to the Magnus effect asso ciated with wave-induced circulation. (C) 1997 Elsevier Science Ltd.