Roll damping to improve the operational limits of existing barge shaped vessels

Roll motion damping has been an important issue since mankind started building ships. Naval architects have always tried to reduce the roll motion as much as possible for comfort, structural strength and operational limits. In this thesis the effects of using ballast water as active or passive roll damping system are investigated. The goal is to improve the motion behavior of barge shaped vessels owned by Boskalis, such as the Taklift 6. These vessels are used extensively on the North Sea. The roll behavior in waves is quite critical for the operational limits, so being able to reduce those motions with a damping system could improve the workability. The North Sea is a region where the most common wave frequency and the eigenfrequency of most barge shaped vessels owned by Boskalis are very close to each other, which may cause severe roll motion even with relative low waves. In this thesis the vessel 'Taklift 6' has been simulated with an active and passive damping system. The time domain simulations have been performed using the software 'OrcaFlex', while the damping system is programmed as an extension to OrcaFlex in the programming language Python. Both the active and passive system show improvement in motion behavior; the spectral density for the roll motion decreases. As a result the operational limits and thus the workability of the vessel can be increased. The increase in operational limits is not very significant though. The increase in operational limit is theoretically interesting, but in reality the improvement is probably not significant enough to make an actual difference in workability. The active system performs only slightly better than the passive system in some simulated cases, and performs worse in other cases. This might be an optimization error as the controller has only been tuned manually. The advantage of an active system would be to be able to compensate for small motions and to be able to respond earlier to vessel motions, but a passive system might be a better fit, as it damps the roll behavior while the complexity of a passive system is simpler compared to an active system and no external power is required. Within the passive system, the motion of the mass could be limited by using air valves on top of each tank to create a semi-passive system. The semi-passive system is not researched within this thesis report. Further model tests should be performed to test the best setup for a damping system. The location and space required might be an issue on some vessels and the effect of different location for the damping system should be researched. Overall a damping system can give a reduction for the roll motion of barge shaped vessels, but the inprovement in operational limts is not significant. Further research into the design and costs aspects is required to make a decision whether a damping system would be beneficial to use in barge shaped vessels. The damping controller should also be improved to optimize the damping behavior and include sloshing effects in the simulations.Floating offshore structuresOffshore and Dredging EngineeringMechanical, Maritime and Materials Engineerin