Motion of a Floating Structure in Water of Uniform Depth

Abstract

A potential flow theory is used to develop a method and an associated computer program that computes the hydrodynamic forces and six degrees-of-freedom motion for floating structures of general configuration at arbitrary heading in waves in water of uniform depth. The hydrodynamic force equation derived become identical, under certain assumptions, to the equations commonly used by the offshore industry, and the two approaches are compared in detail. The computed motions for all six degrees of freedom agree well with model-scale and full-scale experimental data for two typical semisubmersible drilling rigs in finite-depth water. Also, the present motion computations are more accurate than a prior work using the second approach; they use experimentally validated or determined values of hydrodynamic coefficients with the effect of the free surface and water depth included. The present method generates sufficient computation accuracy to use for practical design applications.