Viscous Mean Drift Forces on Moored Semi-Submersibles

摘要

Experimental investigations have been carried out with fixed vertical surfacepiercing model cylinders and a submerged pontoon in regular waves. Test results validate the theory with a further indication that the mean forces on completely submerged bodies are not influenced significantly by viscous effects in a waves-only field. Finally, experiments have been carried on for a complete semisubmersible model (ITTC Model) in regular waves (both head and beam seas) in fixed and free floating conditions at zero speed and with forward velocity. The theory, incorporating a relative horizontal velocity and relative surface elevation concept, enhances the theoretical predictions for the horizontal mean drift forces when experimentally obtained values of the mean drag coefficients for the cylinders and the submerged pontoon are properly applied for the complete semi-submersible.