Roll-yaw coupling effects on parametric resonance for a ship in regular waves

This work represents a further step of the physical study documented by Greco and Lugni (2012b) and Greco et al. (2014). Three-dimensional experiments have been performed on a FPSO model in regular waves to investigate the occurrence of parametric roll, the occurrence and features of water on deck and bottom slamming and the sensitivity of the mid-ship bending moment experienced by the vessel to the different operational conditions examined. The model tests provide also a certified database for the validation of the simplified Domain-Decomposition (DD) solver developed for the prediction of the ships behavior, in regular and long-crested irregular waves and with and without forward speed, documented in detail by Greco and Lugni (2012a). The DD couples a weak-scatterer potential-flow solver for the seakeeping problem with a shallow-water approximation for the water flow on the deck, when water shipping occurs, and with a Wagner-type impact solution, in case of bottom impact. The latter needs a proper criterion, this compound method combines the Ochi’s criterion based on the impact velocity with a pressure criterion proposed by Greco and Lugni (2012a) and validated in many incident-wave cases by Greco et al. (2012). In the previous steps, head-sea conditions, i.e. β = 180, were investigated. Here the cases with β = 175◦ are considered with focus on parametric roll. The comparison between experimental and numerical wave-body interactions, and a subsequent in-depth analysis of the model tests, highlighted some important insights of parametric roll in connection with roll coupling with yaw. These aspects are examined in the following after a brief description of the model tests for the conditions and variables of interest.