HYDROELASTICITY OF SHIPS FREE DOWNLOAD

The predicted bending moments for the S containership models show improved agreement with experimental measurements, especially for the flared model. Structural dynamics concepts such as mode shapes, natural and resonant frequencies are not encompassed by the rigidity restriction 5. The practical relevance of local and global responses must be considered within the framework of structural dynamic response section5. This is illustrated in this section by analysing the global hydroelastic response induced by wet-deck slamming on a catamaran whipping effect. This is consequence of the small ratio between the significant local and global structural natural periods. This is achieved by acknowledging the importance of free surface memory effects, i. Comparisons between time and frequency domain techniques have shown that the effects of non-linearities become particularly important at high speeds.

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Overall, the anti-symmetric natural frequencies for the first few mode shapes calculated with the shell and beamfd models are lower than the corresponding predictions obtained using beamfde but higher for the remaining few Table 2.

Table 6 lists of the longitudinal aluminium transducer and the steel spring hydroelasticiyt quite close and were therefore modelled as 3 2 all data for the ship segments. No structural damping ratios are predicted. This analysis makes use of a three-dimensional finite element model of the structure dry analysis and a pulsating source distribution over its mean wetted surface wet analysis Figure 4.

Hydroelasticity

It hyddoelasticity from the resulting experimental global loads that the variations in peak value of the slamming force have a minor influence on the global loads. Hence, the calculation of the source strength allows for the determination of the fluid pressure and forces acting on the moving hull.

The damping ratio obtained from the dry decay tests is significantly smaller to the corresponding wet ratios. There is good overall agreement for the symmetric wave-induced loads Figs.

Hydroelasticity of ships: recent advances and future trends - ePrints Soton

Recent applications to trimarans [88] also showed good agreement with flexible model experiments for wave induced loads, such as prying moment, for a range of speeds and headings. Significant deviations arise between the antisymmetric dynamic loads predicted by beam and shell model.

The ratios between slamming duration Td and natural periods TN for heave, pitch, two-node and three-node bending are presented in Table 9. Fathi et al [92] carried out a hydroelastic analysis of container vessels.

To ensure hydroealsticity numerical stability [91], the inertia distribution was facilitated via manipulation of the mass elemental density in each section.

In Table 6, 'Xcog' represents the distance from the local centre of gravity Oi Figure 23 of the ship segment to the front end of the catamaran. Account Options Sign in.

Three lowest modes included. Since the response behaviour depends on several factors, these results should not be generalized without further investigation. The results for the surge pressure mode showed a way to obtain external hydrodynamic coefficients for use in computing the internal surging motions of the cargo.

Hydroelasticity of ships: recent advances and future trends

The representation of ship hulls by conformal mapping functions, Journal of Ship Research, For a significant number of headings it appears that linear predictions are closer to the experimental measurements than the predictions including non-linearities. However, i it has shortcomings in hydroelaxticity the coupling between horizontal bending hydroealsticity torsion, ii it does not account for any distinction between centroid and shear centre and iii neglects the warping of cross sections.

Stress responses are verified against strength criteria of yielding, buckling and ultimate ehips as well as fatigue life. As a result the two-dimensional hydroelasticity theory was developed separately for these two cases, ignoring surge, when considering symmetric motions and distortions [4, 8].

Applications to non-slender, mono-hull vessels, such as sailing yachts, demonstrated that the method is capable of accurately simulating the dynamic behaviour of such vessels and correctly identifying areas where structural problems may shlps [89].

The three components of translation are known as surge, heave and sway. An Introductory Review to Hydroelasticity of Ships: Specific formulations allowed the calculation of the radiation forces due to impulsive accelerations, velocities and displacements.

The total dynamic system is solved in the time domain by a modal-based method including heave, pitch, two-node and three-node vertical bending modes.

The vertical plane or longitudinal motions surge, heave nydroelasticity pitch are uncoupled from the horizontal plane or transverse motions sway, roll and yaw. During this study, the flexible test model was converted from a rigid catamaran by cutting it into pieces which were then reconnected with flexible couplings.

If the wet-deck has a bow ramp and the tendency is that the water will hit at the front end of the wet-deck, larger relative motion amplitude is needed for impact relative to a flat deck. In order to match the experimental slamming force peaks Fig. These differences indicate an influence from warping-induced stresses, referred to as the bi-moment [] that should be accounted for when comparing modal horizontal bending or torsion moment, obtained hydroelasticitu beam and shell idealisations.

Full text not available from this repository. University of Southampton Institutional Repository.