Abstract
This paper describes the development of alternative time domain numerical simulation methods for predicting large amplitude motions of ships and floating structures in response to incoming waves in the frame of potential theory. The developed alternative set of time domain methods simulate the hydrodynamic forces acting on ships advancing in waves with constant speed. For motions’ simulation, the diffraction forces and radiation forces are calculated up to the mean wetted surface, while the Froude‐Krylov forces and hydrostatic restoring forces are calculated up to the undisturbed incident wave surface in case of large incident wave amplitude. This enables the study of the above waterline hull form effect. Characteristic case studies on simulating the hydrodynamic forces and motions of standard type of ships have been conducted for validation purpose. Good agreement with other numerical codes and experimental data has been observed. Furthermore, the added resistance of ships in waves can be calculated by the presented methods. This capability supports the increased demand of this type of tools for the proper selection of engine/propulsion systems accounting for ship’s performance in realistic sea conditions, or when optimizing ship’s sailing route for minimum fuel consumption and toxic gas emissions.
Highlights
The accurate prediction of the seakeeping behavior of ships and offshore structures in real seas is a demanding task for naval architects and of great practical interest to shipbuilders, owners/operators, as it affects both their design and operation.Quasi 2D strip theory approaches to the seakeeping of ships were the first which delivered satisfactory results for practical applications to the prediction of wave-induced loads and motions, and they are widely used even today
This paper describes the development of alternative time domain numerical simulation methods for predicting large amplitude motions of ships and floating structures in response to incoming waves in the frame of potential theory
A part of the free surface is included in the inner domain, which needs updating at each time step
Summary
The accurate prediction of the seakeeping behavior of ships and offshore structures in real seas is a demanding task for naval architects and of great practical interest to shipbuilders, owners/operators, as it affects both their design and operation.Quasi 2D strip theory approaches to the seakeeping of ships were the first which delivered satisfactory results for practical applications to the prediction of wave-induced loads and motions, and they are widely used even today. Lin and Yue 3 showed the applicability of a time domain Green function method to large amplitude ship motions Following this formulation, Singh et al 4 appeared to have obtained good results in some applications. Duan and Dai 5 found that the commonly used panel method employing the transient Green function for a non-wall-sided floating body does not satisfy the mean-value theorem of definite integrals for the near-water surface panels and solved this problem by introducing an imaginary vertical surface, which encloses the hull surface in the fluid domain. This method works fine, unless the body has some bulb-like hull form, which exceeds the projection of the water plane. There is a slight overlap between the two introduced domains, which creates a matching domain
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