The aim of the package GL-RollBest in the entire project is the development, implementation and validation of an efficient procedure for the calculation of roll damping. The roll moment can be separated into two parts: one, in phase with the roll motion (righting and inertial moments), can be calculated with potential methods. The second part, in phase with roll velocity (damping), consists of two major components. The first component due to wave radiation by the rolling ship can also be defined with potential methods, while the second, viscous component is dominating and should be defined with the developed procedure. This component is assumed independent of roll frequency for relatively small roll frequencies, typical for the majority of ships. Therefore, the viscous contribution to roll damping can be derived from a numerical simulation of the flow around a steadily rotating double body in a uniform flow, accounting for the forward speed of the ship. In the coordinate system rotating with the ship, the flow can be treated as steady; this reduces significantly the required computational time, while allowing resolution of the most important viscous (e.g. scale) effects.
The calculation procedure will be validated against model tests in a towing tank and a wind channel, as well as nonsteady RANSE simulations with the free surface, and will be used as a practical tool for the definition of roll damping.
