Automatic waterline registration of a ship model in waves

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Parametric rolling in regular head waves of the Kriso container ship : numerical and experimental investigation in shallow water

The IMO Intact Stability Code considers the parametric rolling phenomenon as one of the stability failure modes because of the larger roll angles attained. This hazardous condition of roll resonance can lead to loss of cargo, passenger discomfort, and even (in the extreme cases) the ship's capsize. Studies as such are mostly conducted considering wave characteristics corresponding to wave lengths around one ship length (lambda approximate to L-PP) and wave amplitudes varying from moderate to rough values. These wave characteristics, recognised as main contributors to parametric rolling, are frequently encountered in deep water. Waves with lengths of such magnitudes are also met by modern container ships in areas in close proximity to ports, but with less significant wave amplitudes. In such areas, due to the limited water depth and the relatively large draft of the ships, shallow water effects influence the overall ship behaviour as well. Studies dedicated to parametric rolling occurrence in shallow water are scarce in literature. In spite of no accidents being yet reported in such scenarios, its occurrence and methods for its prediction require further attention; this in order to prevent any hazardous conditions. The present work investigates the parametric roll phenomenon numerically and experimentally in shallow water. The study is carried out with the KRISO container ship (KCS) hull. The numerical investigation uses methods available in literature to study the susceptibility and severity of parametric rolling. Their applicability to investigate this phenomenon in shallow water is also discussed. The experimental analysis was carried out at the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University). Model tests comprised a variation of different forward speeds, wave amplitudes and wave lengths (around one L-PP). The water depth was fixed to a condition equivalent to a gross under keel clearance (UKC) of 100% of the ship's draft

Integrability of natural Hamiltonian systems with homogeneous potentials of degree zero

We derive necessary conditions for integrability in the Liouville sense of natural Hamiltonian systems with homogeneous potential of degree zero. We derive these conditions through an analysis of the differential Galois group of variational equations along a particular solution generated by a non-zero solution \vd\in\C^n of nonlinear equations \grad V(\vd)=\vd. We proved that if the system integrable then the Hessian matrix V''(\vd) has only integer eigenvalues and is semi-simple.Comment: 13 page

Wave effects on the turning ability of an ultra large container ship in shallow water

The influence of waves on ship behaviour can lead to hazardous scenarios which put at risk the ship, the crew and the surroundings. For this reason, investigating the effect of waves on manoeuvring is of relevant interest. Waves may impair the overall manoeuvring performance of ships hence increasing risks such as collisions, which are of critical importance when considering dense traffic around harbour entrances and in unsheltered access channels. These are conditions met by Ultra Large Container Ships (ULCS) when approaching a port, e.g. in the North Sea access channels to the main sea ports of Belgium. Note that due to the large draft of ULCS and the limited water depth, shallow water effects will also influenced the ship. Thus, in such scenarios the combined effects of shallow water and waves on the ship's manoeuvring need to be studied. The present work investigates the effect of waves on the turning ability of an ULCS in shallow water. Simulations are carried out using the two time scale approach. The restricted water depth corresponds to 50% Under Keel Clearance (UKC). To gain a better insight on the forces acting on the ship, the propulsion, and the rudder behaviour in waves experimental studies were conducted. These tests were carried out in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University) with a scale model of an ULCS. Different wave lengths, wave amplitudes, ships speeds, propeller rates, and rudder angles were tested. The turning ability characteristics obtained from simulations in waves and calm water are presented, and discussed

3D models related to the publication: Comparative anatomy and phylogenetic contribution of intracranial osseous canals and cavities in armadillos and glyptodonts (Xenarthra, Cingulata)

INTRODUCTION: The phylogeny of the Cingulata has been debated in morphological analyses for a long time (Engelmann, 1985; Gaudin &Wible, 2006; Billet et al., 2011; Delsuc et al., 2016; Mitchell et al., 2016; Herrera et al., 2017) and this incongruence was enriched by the contribution of recent molecular analyses (Delsuc et al., 2016; Mitchell et al., 2016). This is particularly the case for the emblematic group of glyptodonts whose mitochondrial genome was recently assembled (Delsuc et al., 2016; Mitchell et al., 2016). Although the cranial anatomy is relatively well known in xenarthrans, their internal cranial anatomy remains poorly studied. Yet, several studies have shown that their exploration provides systematic interest on their past and present diversity (Zurita et al., 2011; Fernicola et al., 2012; Billet et al., 2015; Tambusso & Fari˜na, 2015a; Tambusso & Fari˜na, 2015b; Billet et al., 2017; Boscaini et al., 2018; Boscaini et al., 2020; Tambusso et al., 2021). In a recent study (Le Verger et al., 2021), we describe and compare 8 cranial canals (involved in the vascularization and innervation of the cranium) and alveolar cavities (Figure 1) of 30 specimens belonging to the Cingulata. In this sampling, all extant subfamilies are represented and several large fossil groups including giant forms such as pampatheres and glyptodonts are represented. For the latter, the oldest complete crania have been studied. A sloth and an anteater were also added to the sample as outgroup. Of the total sample, 3D models of 13 specimens are made available (Table 1). The rest of the specimens are available only upon request from LGR. In this study (Le Verger et al., 2021), we present the comparativ investigation of these intracranial osseous canals and alveolar cavities using X-ray microtomography. Their 3D virtual reconstruction enabled us to compare the locations, trajectories, and shape of each homologous structure and discuss their potential interest for cingulate systematics