Application of 2D hydroelasticity theory to investigate the failure of a containership

This paper focuses on the investigation carried out on the failure of the MSC Napoli using two-dimensional (2D) symmetric (i.e. vertical bending) hydroelasticity analysis. The aim of the investigation was to assess the influence of whipping-induced loads on the structural strength of this containership. Relevant structural, hydrostatic and operational data were provided. The calculations were carried out in head regular and long-crested irregular waves. Both cases included the effect of bottom slamming only. Global wave-induced loads were evaluated along the hull, focusing in particular in the vicinity of the engine room. The investigation showed that whipping, due to bottom slamming, is only important for severe seas. The investigation also showed that the keel stresses, in way of the engine room, can be as large as the keel stresses at amidships

Numerical simulation of liquid sloshing in LNG tanks using a compressible two-fluid flow model

In this investigation the Reynolds-Averaged Navier-Stokes (RANS) equations are modified to account for variable density and viscosity of the two-fluids flow (i.e. water-air), assuming both fluids compressible. By introducing a preconditioner, the governing equations in terms of primitive variables are solved for both fluids in a unified manner. The non-conservative implicit Split Coefficient Matrix Method (SCMM) is modified to approximate convective flux vectors in the dual time formulation. The free surface waves inside the tank, due to sloshing, are implicitly captured by using a level set approach. The method is illustrated through applications to rectangular and chamfered tanks subject to sway or roll motions at different filling levels and excitation conditions (i.e. amplitude and frequency of oscillation). Comparisons are made between calculated and experimental pressures, where available

The effect of structural discontinuity on antisymmetric response of a container ship

Recent trends in capacity, hence size, growth in container ships have increased the importance of torsion, particularly how it is influenced by the large deck openings and structural discontinuities present in such ships. This paper investigates the consequences of these effects on the ‘dry’ antisymmetric modal characteristics and consequent wave-induced loads. A beam model with more accurate representation of warping and structural discontinuities is applied to a box beam to assess these influences and compare predictions of natural frequencies and mode shapes with previous calculations and finite element (FE) predictions. The analysis is subsequently applied to a feeder containership travelling in regular oblique waves and resultant loads are compared with predictions obtained from previous two (2D) - and three-dimensional (3D) hydroelasticity analyses

Smoothed Particle Hydrodynamics (SPH) method for modelling 2-dimensional free surface hydrodynamics

The main goal of the current research is to implement Smoothed Particle Hydrodynamics (SPH) for the prediction of wave-induced motions and loads within the framework of 3D modelling. In this paper, the focus is twofold. First, implementation of possible additional terms to the standard incompressible SPH (ISPH) method with reference to generating/propagating regular waves in 2D domain, using a piston wave maker. Improvements to the prediction of pressure and velocity fields are then carried out with kernel renormalization technique and shifting technique without increasing the computational cost. The arc method is employed to improve the accuracy of free surface recognition, i.e. “noise-free” free surface. In addition, the weakly compressible (WCSPH) is also applied to the problem of 2D regular wave generation. Comparisons of predicted free surfaces, their kinematic and dynamic characteristics between ISPH, WCSPH and analytical so-lutions for a range of frequencies are carried out. The second focus of the paper is the 2D radiation problem due to forced sinusoidal oscillation of a rectangular section floating on calm water. The predicted hydrody-namic actions and coefficients in sway by WCSPH are then compared against available experimental meas-urements

Hydroelastic analysis of flexible barge in regular waves using coupled CFD-FEM modelling

The aim of this paper is to investigate the wave-body interaction of flexible floating bodies by coupling RANS/CFD and Finite Element software. A combination of overset and morphing approaches and finite volume solution to allow for the motion of a barge at the free surface is used. Results are presented for the motion response of the three-dimensional (3-D) barge, treated both as rigid and flexible body, in regular head waves using STAR-CCM+, the latter carried out by a two-way coupling between Star-CCM+ and Abaqus. To illustrate this application, the structure of the flexible barge is modelled as a beam, in line with the flexible backbone model used in experiments. The RAOs of vertical displacements, at a number of positions along the barge, calculated using this coupling technique are compared against experimental measurements and two-dimensional (2-D) linear hydroelasticity predictions

Added mass and damping coefficients for a uniform flexible barge using VOF

The main aim of this paper is the numerical investigation of the effect of domain size and mesh density on modeling the three-dimensional (3-D) the radiation problem using RANS CFD software. The solution for the radiation forces and moments, namely the added mass and damping coefficients, is obtained by imposing a simple harmonic oscillation to a marine structure floating in still water at the relevant mode shape. A uniform barge is used to illustrate the investigation, with the relevant symmetric mode shapes provided from the Euler beam theory. The hydrodynamic coefficients for symmetric oscillations of the barge are evaluated using an inviscid flow model in STAR-CCM+. These include the rigid body motions of heave and pitch and the 2- and 3-node distortion mode shapes. A range of mesh densities, between 1.1M and 9.6 M, are used to examine their effects with particular reference to low and high frequencies and the cross-coupling hydrodynamic coefficients between rigid and distortion modes. The influence of the damping zone on the solution is also examined. The RANS CFD predictions are compared with the results from a three-dimensional potential flow boundary element method, allowing for hull distortions

Coupled fluid structure interaction to model three-dimensional dynamic behaviour of ship in waves

Increase in computational power over the recent years has made it possible to investigate fluid-structure interaction problems using RANS/CFD and Finite Element software. However, the majority of these investigations are carried out using one-way coupling, thus omitting important fluid-structure interactions. A strong or two-way coupling between RANS/CFD and FEA is presented in this paper to model symmetric motion and response of flexible floating bodies in regular head waves. To illustrate this application, the RAOs of vertical displacements and wave-induced loads are calculated at various locations along a flexible three-dimensional barge (3-D) barge. The structure of the flexible barge is modelled as beam, in line with the flexible backbone model used in the experiments. The computational results are compared with experimental measurements and two-dimensional (2-D) linear hydroelastic predictions. A preliminary investigation for the static, still water, response of a flexible S-175 container ship model is also presented

Experimental measurements of hull pressures on fast displacement catamarans during motions in long-crested head-seas

Piezoresistive pressure transducers have been used to measure the pressure variations at six points on a catamaran hull moving in regular, long-crested, head-seas. Preliminary results demonstrate the feasibility of this experimental approach although a more refined experimental procedure may be required to obtain greater accuracy in the pressure measurements.The pressure measurements were carried out for one demihull spacing at two speeds in calm water and also in regular waves of differing wave periods. The mean pressures from both calm water and regular wave tests are presented along with the RMS variation from the mean during the tests in regular waves

Comparison of experimental and numerical sloshing loads in partially filled tanks

Sloshing phenomenon consists in the movement of liquids inside partially filled tanks, whichgenerates dynamic loads on the tank structure. Resulting impact pressures are of great importance in assessingstructural strength, and their correct evaluation still represents a challenge for the designer due to the highnonlinearities involved, with complex free surface deformations, violent impact phenomena and influence of airtrapping. In the present paper a set of two-dimensional cases for which experimental results are available areconsidered to assess merits and shortcomings of different numerical methods for sloshing evaluation, namely twocommercial RANS solvers (FLOW-3D and LS-DYNA), and two own developed methods (Smoothed ParticleHydrodynamics and RANS). Impact pressures at different critical locations and global moment induced by watermotion for a partially filled tank with rectangular section having a rolling motion have been evaluated and resultsare compared with experiments