The Hydrodynamics of Floating Compound Cylinders

Abstract

The hydrodynamics of a freely floating compound cylinder consisting of a surface-piercing cylindrical column resting on a larger, concentric cylindrical base are investigated theoretically. Linear wave theory and small-amplitude structural oscillations are assumed, and an eigenfunction expansion approach is used to obtain semi-analytical expressions for the hydrodynamic excitation and reaction loads on the structure. Numerical results are presented for a range of wave and structural parameters. It is found that for certain parameter combinations, negative surge/sway added mass coefficients are predicted. The numerical results for the hydrodynamic quantities obtained by the eigenfunction approach have been verified with those obtained by the linear radiation/diffraction program UHWAVE. These results have implications for the tow-out analysis of large gravity-base oil production platforms.

Hydrodynamic coefficients for a floating semi-porous compound cylinder in finite ocean depth

“…The obtained results are validated by comparing one result with an available result (Williams and Li [28]) and a satisfactory agreement is noticed thereby implying the effectiveness of the mathematical model and subsequent results of the present work.…”

“…To validate our present analytical model developed for solving the problem, we deem it suitable to compare one of the results with that of Williams and Li [28], i.e., when the cylinder is considered to be a floating compound cylinder (the curved surface of the bottom cylinder is considered impermeable). The relevant parameters in our problem are reconsidered conforming to the work of Williams and Li in order to convert to the same physical problem.…”

“…They found that added mass became negative when the depth of submergence was small and free surface effects were remarkable. Williams and Li [28] investigated hydrodynamic forces and coefficients for a freely floating compound cylinder consisting of a surface-piercing cylindrical column resting on a larger, concentric cylindrical base. For certain parameter combinations, negative surge/ sway added mass coefficients were observed.…”