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Shipbuilding and Navigation in India Prior to 1500
Published in K.S. Mathew, Shipbuilding, Navigation and the Portuguese in Pre-modern India, 2017
The stem was the extreme front of a ship. Its size depended on the shape of the ship and usually had a 7 inch slant. A vessel of 110 feet had an amaram of 35 feet height and an aniyam of 24 feet. These were fixed before the ribs were finally placed. Amaram was at the extreme back of a boat. It was controlled by a sculler or Amarakkaran.
A combined approach based on Subdivision Surface and Free Form Deformation for smart ship hull form design and variation
Published in Ships and Offshore Structures, 2018
Antonio Coppedé, Giuliano Vernengo, Diego Villa
Figure 1 displays an example of subsequent subdivisions of a portion of a hull surface. The shape represented is the extreme bow of a hull with a bulb. It has been chosen due to the relative complexity of its shape (compared to the rest of the hull). In fact double curvatures both in longitudinal and vertical directions are present. Moreover, the connection on the longitudinal symmetry plane between the bulb and the bow of the hull, ideally considered without the bulb itself, known as stem post, is a point that usually creates issues in a modelling phase. The algorithm starts from a coarse mesh, shown in Figure 1(a), whose vertexes can be considered as the control points of the final surface. The portion of the surface highlighted in green, made of two quadrangular and two triangular elements, as the whole surface mesh, is subdivided according to the Quad-Tri algorithm: each edge is split into two pieces, each quadrangular and triangular element in four and three sub-elements, respectively. The new positions of each vertex of the subdivided mesh are then computed as weighted combination of the vertex itself and those of its neighbours, as schematically shown in Figure 1(b).
Simplified contact-based segment expansion (CBSE) method for assessment of crashworthiness of double-hulled ship structure
Published in Ships and Offshore Structures, 2022
Han-Baek Ju, Beom-Seon Jang, Junhwan Choi, Jung Kim, Sang-Bae Jeon
Figures 6 and 7 display the von-Mises stress distribution of the double-hulled structure for the collisions in the bulbous bow and stem cases, respectively. The stress on the outer hull was more widely distributed in the bulbous bow case than in the stem case. In the bulbous bow case, the stress spread in all directions around the first contact point at which the penetrative displacement arose at the initial stage. This was due to the axisymmetric and rounded shape of the bulbous bow. However, the spread of the high stress zone was limited due to the overall slender shape, even though the penetration went deeper.
The influence of the bow design on structural response due to ice loading
Published in Ships and Offshore Structures, 2018
Jonas Warntjen, Sandro Erceg, Henry Piehl, Sören Ehlers
Some of the advantages come with a drawback as well, like the requirement of Boolean operations for creation of intersections at the position of the transversal stiffeners. This requires additional computational power. Furthermore, occasionally unstable geometric operations at complex surface intersections occur, e.g. the connection of the stem line and keel line.