Doo-Yeoun Cho

An algorithm for automatic 2D quadrilateral mesh generation with line constraints

Finite element method (FEM) is a fundamental numerical analysis technique widely used in engineering applications. Although state-of-the-art hardware has reduced the solving time, which accounts for a small portion of the overall FEM analysis time, the relative time needed to build mesh models has been increasing. In particular, mesh models that must model stiffeners, those features that are attached to the plate in a ship structure, are imposed with line constraints and other constraints such as holes. To automatically generate a 2D quadrilateral mesh with the line constraints, an extended algorithm to handle line constraints is proposed based on the constrained Delaunay triangulation and Q-Morph algorithm. The performance of the proposed algorithm is evaluated, and numerical results of our proposed algorithm are presented.

Interpolating G1 Bézier surfaces over irregular curve networks for ship hull design

We propose a local method of constructing piecewise G^1 Bezier patches to span an irregular curve network, without modifying the given curves at odd- and 4-valent node points. Topologically irregular regions of the network are approximated by implicit surfaces, which are used to generate split curves, which subdivide the regions into triangular and/or rectangular sub-regions. The subdivided regions are then interpolated with Bezier patches. We analyze various singular cases of the G^1 condition that is to be met by the interpolation and propose a new G^1 continuity condition using linear and quartic scalar weight functions. Using this condition, a curve network can be interpolated without modification at 4-valent nodes with two collinear tangent vectors, even in the presence of singularities. We demonstrate our approach in a ship hull.

DEVELOPMENT OF A SOPHISTICATED HULL FORM CAD SYSTEM "EZHULL" BASED ON A NON-MANIFOLD MODEL AND "X-TOPOLOGY"

Publisher Summary The EzHULL system developed in this chapter provides an association based cross fairing and surface generation, using X-topology and nonmanifold data structure. X-topology is the data structure for a wireframe model that supports the association based cross fairing. The association based cross fairing offers designers an effective wireframe fairing by monitoring how adjacent lines are affected when a particular line is changed. Direct conversion from a wireframe model to a surface model enables 3D surface hull form to be visualized even at the earliest design stages. The topological information of the converted surface model helps to resolve the points ordering problem in the wireframe model, and the geometric information is used to shade the wireframe model with a cubic effect. In addition to these features, EzHULL also provides convenient and intuitive wireframe editing system for planar and spatial curves, hull form variations, and various facilities for hull form design. The geometric data of the surface model can be used to display the 3D surface hull form to check the surface fairness at the early design stage of hull form. The topological information can be used to solve the points ordering problem that occurs in the wireframe based design system. An example of a twin skeg hull form showing the effectiveness of the developed system is included.

Block Erection Simulation Using the Integrated System of Combined Discrete Event and Discrete Time Simulation Kernel

Recently, requests for the accurate process planning using modeling and simulation technique are increasing in many engineering fields including shipbuilding industry. In this study, Combined DEVS(Discrete EVent System specification) and DTSS(Discrete Time System Specification) simulation kernel is developed, and an integration strategy of dynamics simulation module and graphics module is also implemented. To evaluate the efficiency and applicability of the simulation kernel and integration strategy, these are applied to the block erection simulation of offshore structures.

Analysis and avoidance of singularities for local G 1 surface interpolation of Bézier curve network with 4-valent nodes

We propose a local method of constructing piecewise G1 Bézier patches to span a Bézier curve network with odd- and 4-valent node points. We analyze all possible singular cases of the G1 condition that is to be met by the curve network interpolation and propose a new G1 continuity condition using linear and quartic scalar weight functions. Using this condition, a curve network can be interpolated without modification at 4-valent nodes with two collinear tangent vectors, even in the presence of singularities. We demonstrate our approach by generating G1 surfaces over the curve network which includes singularities at its node vertices and edges.

Optimal Block Transportation Path Planning of Transporters considering the Damaged Path

Nowadays, a transporter manager plans the schedule of the block transportation by considering the experience of the manager, the production process of the blocks and the priority of the block transportation in shipyard. The schedule planning of the block transportation should be rearranged for the reflection of the path blocking cases occurred by unexpected obstacles or delays in transportation. In this paper, the optimal block transportation path planning system is developed for rearranging the schedule of the block transportation by considering the damaged path. algorithm is applied to calculate the new shortest path between the departure and arrival of the blocks transported through the damaged path. In this algorithm, the first node of the damaged path is considered as the starting position of the new shortest path, and then the shortest path calculation is completed if the new shortest path is connected to the one of nodes in the original path. In addition, the data structure for the algorithm is designed. This optimal block transportation path planning system is applied to the Philippine Subic shipyard and the ability of the rapid path modification is verified.

A tracing algorithm for surface-surface intersections on surface boundaries

In this paper we present an algorithm with a new trace-terminating condition for tracing along surface-surface intersection curves on surface boundaries, while several tracing methods and embedding methods that include tracing scheme may cause false termination with a traditional trace-terminating condition: tracing stops when the surface-domain’s boundary is reached. And we also suggest another iterative method to calculate intersection points on surface boundaries with parallel surface normal. Some numerical examples with these two ideas and comparisons to ‘DESIGNBASE’, ‘ACIS’, and ‘Parasolid’ are included to demonstrate the effectiveness of our algorithm.

Generation of Discrete Bicubic G1 B-Spline Ship Hullform Surfaces from a Given Curve Network Using Virtual Iso-Parametric Curves

We propose a method that automatically generates discrete bicubic G1 continuous B-spline surfaces that interpolate the curve network of a ship hullform. First, the curves in the network are classified into two types: boundary curves and “reference curves”. The boundary curves correspond to a set of rectangular (or triangular) topological type that can be represented with tensor-product (or degenerate) B-spline surface patches. Next, in the interior of the patches, surface fitting points and cross boundary derivatives are estimated from the reference curves by constructing “virtual” iso-parametric curves. Finally, a discrete G1 continuous B-spline surface is generated by a surface fitting algorithm. Several smooth ship hullform surfaces generated from curve networks corresponding to actual ship hullforms demonstrate the quality of the method.

An Operation Scheduling of Transporters Considering Turns and Passing Delay at the Intersection Roads on the Shipyard

An Operation Scheduling of Transporters Considering Turns and Passing Delay at the Intersection Roads on the Shipyard Jong-Heon Moon .Won-Sun Ruy .Doo-Yeoun Cho Graduate School, Dept. of Naval Architecture & Ocean engineering, Chungnam National University Dept. of Naval Architecture & Ocean Engineering, Chungnam National University Dept. of Naval Architecture & Ocean Engineering, Mokpo National University

Methods for the Modularization of Simulation Model and the Management Scheme of Simulation Scenario for Shipbuilding Process Planning

Recently, requests for accurate process planning using simulation have been increasing in many engineering fields including the shipbuilding industry, and many application systems for simulation have been developed. It is difficult, however, for a user to reuse the developed systems, because simulation models in the system are defined by its own method. In addition, the simulation model should be modified whenever a simulation sequence, which is called simulation scenario, is changed. Therefore, in this study, an elementary simulation object is proposed to modularize a simulation model. And the management scheme of simulation scenario is proposed to manage the scenario outside of the simulation models. Also, a simulation template is proposed to increase the development efficiency. To verify the efficiency of the proposed methods, application examples for shipbuilding process planning are implemented.