Linear potential theories have proved to be efficient tools to predict linear floating structure motions. A known exception to this is the roll motion of ship-like structures near the resonant frequency range, where codes based on potential theories commonly overestimate the responses.

The roll damping moment could include a number of components, such as the wave induced, lift, friction, eddy, and the appendage contributions. The wave and lift components are linear, and are proportional to the roll angular velocity. The hull surface frictional damping for a full size ship-like structure is negligible; the major contributions are the radiation damping, nonlinear bilge vortex shedding damping, and bilge keel damping [21].

It is common practice for the calculation of nonlinear roll damping to use estimation methods or experimental data to account for the viscosity effect.