Description of ship motion and comparison of a real-time unified hydrodynamic model with free running tests in calm water and regular waves

Abstract

Ship bridge simulators are well established in education practices of seafarers and mariners. The use of simulators in research is ramping up due to the EU motivation towards Blue Growth, where the quantity and quality of offshore operations are evolving. There is a need of deeper understanding of ship motion in waves within hydrodynamics research. Simulators solve both the seakeeping and maneuvering problems simultaneously in order to represent the ship response in real-time. Methods that solve both the seakeeping and maneuvering are referred to as unified models. This study will present and describe ship motion, in calm water and regular waves, as experimented in free running maneuvering model tests (Rabliås & Kristiansen, 2019) and will compare the result of the model tests with simulations using the unified model; Fossen's vectorial unified model (2005). Fossen's model uses frequency dependent hydrodynamic coefficients and solves ship motion in 6 degrees of freedom, and the fluid memory effects are computed using ShipX (VERES).

This study investigates the performance of a hydrodynamic simulation method in regular incident waves. The container carrier Duisburg Test Case (DTC) hull is considered. Model tests including Zig-Zag 20/20 and Turning Circle maneuvers were performed in the Ocean basin at SINTEF Ocean in Trondheim, Norway. Simulation and experiments cover a range of wavelengths, approaching the vessel from different directions including head seas, beam seas and following seas.

Presentation and description of ship motion in waves is challenging. Appropriate tools are required. Polar scatters were used for describing ship motion in waves. The comparisons show that simulation results are comparable with model tests, however the digital ship is a different ship.