A Fast Algorithm for the Prediction of Ship-Bank Interaction in Shallow Water

The hydrodynamic interaction induced by the complex flow around a ship maneuvering in restricted waters has a significant influence on navigation safety. In particular, when a ship moves in the vicinity of a bank, the hydrodynamic interaction forces caused by the bank effect can significantly affect the ship’s maneuverability. An efficient algorithm integrated in onboard systems or simulators for capturing the bank effect with fair accuracy would benefit navigation safety. In this study, an algorithm based on the potential-flow theory is presented for efficient calculation of ship-bank hydrodynamic interaction forces. Under the low Froude number assumption, the free surface boundary condition is approximated using the double-body model. A layer of sources is dynamically distributed on part of the seabed and bank in the vicinity of the ship to model the boundary conditions. The sinkage and trim are iteratively solved via hydrostatic balance, and the importance of including sinkage and trim is investigated. To validate the numerical method, a series of simulations with various configurations are carried out, and the results are compared with experiment and numerical results obtained with RANSE-based and Rankine source methods. The comparison and analysis show the accuracy of the method proposed in this paper satisfactory except for extreme shallow water cases.

Two-Dimensional Numerical Modelling of a Moored Floating Body under Sloping Seabed Conditions

A coupled floating body-mooring line model is developed by combining a boundary element model for a two-dimensional floating body and a catenary mooring line model. The boundary element model is formulated in the time domain by a continuous Rankine source, and a reflection potential is introduced to account for the wave reflection due to sloping seabed. This newly developed model is validated by comparisons against available data. Then, dynamic response analyses are performed for the moored body in various seabed conditions. Compared with a flat seabed, a sloping seabed causes unsymmetrical mooring line configuration and generates noticeable effects in the motion responses of the floating body.

Hydrodynamic Design Study on Ship Bow and Stern Hull Form Synchronous Optimization Covering Whole Speeds Range

The main objective of this article is to describe an innovative methodology of synchronous local optimization which considers the whole ship speed range being presented for a KRISO Container Ship (KCS). Parametric form approaches are adopted by employing a fairing B-spline curve in order to generate variants of the bow and stern of forms using form design parameters modified, resulting in an optimization system based on NSGA-II. The total resistance is calculated by the Rankine source panel method and the empirical formula which agrees well with the corresponding experimental data and further acquires validation with the overall error of 2.0%. Accordingly, the ship forepart and stern form have been optimized under conditions of the single design speed and whole speeds range based on the considerations of generally distributed and variable operational speeds for the operating characteristics of modern container ships synchronously. The optimized result presents well-balanced drag reduction benefits which averagely remain above 4.0% of ship resistance decrease. Compared to the traditional optimization process which is based on a specific design speed, the newly developed method is more practical and effective in both automation and integration.

Interaction of Fixed Cylinder With Waves Through Weakly Coupled FNPT and Lagrangian Navier-Stokes

This paper presents a 2D/3D hybrid numerical model for studying the interaction of non-breaking waves with cylindrical structure. The work combines the strengths of mesh-based and particle-based methods, where the wave propagation is solved using 2D mesh-based potential theory model and the interaction with the structure is solved using 3D particle-based Navier-Stokes model. The paper presents the formulation of the two models and the weak-coupling methodology, along with recent improvements in the 3D MLPG_R (Mesh-less Petrov-Galerkin based on Rankine source solution) particle based method. The numerical results from interaction of fixed cylinder with solitary and focussed waves are compared with experimental data. The work demonstrates a significant reduction in simulation time for wave-structure interaction problems achieved using this hybrid approach without compromising on accuracy.