SEAKEEPING

Seakeeping is the ability of a vessel to perform its intended functions in various sea conditions. It is an important aspect of naval architecture and marine engineering, as it affects the design of the vessel in terms of its shape, size, weight, strength, stability, propulsion, and control. Seakeeping can be evaluated by various criteria, such as the motions of the vessel, the loads on the structure, the hydrodynamic forces and moments, the propulsive performance, and the maneuverability. Seakeeping analysis can be performed by theoretical methods, numerical simulations, model tests, or full-scale trials. Theoretical methods are based on mathematical models that describe the motion of the vessel and the interaction with the waves. They can be divided into linear and nonlinear methods, depending on whether they account for the effects of large wave amplitudes and vessel displacements. Linear methods are simpler and faster, but they may not capture some important phenomena, such as wave breaking, slamming, green water, or capsizing. Nonlinear methods are more accurate and realistic, but they are also more complex and computationally demanding. Theoretical methods can help to optimize the design of the vessel by predicting its seakeeping performance for different configurations and conditions. Numerical simulations are based on solving the governing equations of fluid dynamics and rigid body dynamics on a computer. They can be classified into potential flow and viscous flow methods, depending on whether they include the effects of viscosity and turbulence. Potential flow methods are more suitable for inviscid and irrotational flows, such as those around slender bodies or in deep water. Viscous flow methods are more suitable for viscous and rotational flows, such as those around blunt bodies or in shallow water. Numerical simulations can help to improve the design of the vessel by providing detailed information on the flow field and the pressure distribution around the hull. Model tests are based on conducting experiments with scaled-down replicas of the vessel in a controlled environment, such as a towing tank or a wave basin. They can provide reliable and realistic data on the seakeeping performance of the vessel, as well as valuable insights into the physical mechanisms involved. However, they also have some limitations, such as the effects of scale, geometry simplification, boundary conditions, and measurement errors. Model tests can help to validate and refine the design of the vessel by comparing its behavior with that of the theoretical and numerical methods. Full-scale trials are based on measuring the actual behavior of the vessel in real sea conditions. They can provide the most accurate and comprehensive information on the seakeeping performance of the vessel, as well as feedback for validating and improving the other methods. However, they also have some challenges, such as the variability and unpredictability of the sea state, the difficulty and cost of instrumentation and data acquisition, and the ethical and environmental issues. Full-scale trials can help to verify and demonstrate the design of the vessel by testing its functionality and operability in realistic scenarios.