International Shipbuilding Progress - Volume 61, issue 1-2

Authors: Guan, Guan | Lin, Yan | Ji, Zhuoshang

Article Type: Research Article

Abstract: The optimal matching of laser measurements in shipyard with the 3D design model for hull blocks is the key to accurately analyze construction errors and rationally offer modification. The conventional registration algorithms tend to neglect the shipbuilding constraints thus cannot meet the practical shipbuilding demands. To solve the problem, this article presents an advanced matching approach under the actual shipbuilding constraints. Firstly, the initial registration values were obtained by the singular value decomposition (SVD) method. Secondly, according to the accuracy requirement, the error distribution at different directions was determined by weight vectors. Lastly, on the basis of initial registration, an …accurate registration that adopted nonlinear multi-objective optimization led to perfect matching by introducing the constraints (e.g. levelness, verticality, flatness and straightness) into the objective function of the computing model. The experimental results proved that the method can obtain the most reasonable matching result satisfying the shipbuilding constraints. It can provide an instructive basis for subsequent assembly. Show more

Keywords: Shipbuilding, ship shape, hull assembly, SVD, multi-objective optimization, accuracy verification

DOI: 10.3233/ISP-130108

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 1-15, 2014

Authors: Razola, Mikael | Rosén, Anders | Garme, Karl

Article Type: Research Article

Abstract: In this paper a methodology that enables detailed studies of the momentary slamming pressure distribution and the related structural loads is presented. The methodology involves pressure measurements, spatial and temporal pressure distribution reconstruction, and finite element analysis. Using a set of model experiments with a high-speed planing craft towed in irregular waves, the methodology is applied to evaluate different slamming pressure models regarding their ability to accurately represent the structure loads. The slamming equivalent uniform pressure model used in the prevailing semi-empirical design methods, and non-uniform time-dependent pressure models used in a method for direct calculation, are considered. It is …concluded that for smaller structure members, typically found in densely spaced metal structures, the uniform pressure model performs well with respect to accurately representing the structure loads. However, for larger members found in modern sandwich structures, the underestimation of structure loads is significant, especially with respect to the shear forces. The non-uniform pressure modeling technique is concluded to be promising regarding its ability to accurately represent the structure loads, regardless of structure member size. The presented methodology is concluded to be a useful tool in further research regarding the evaluation and development of methods for high-speed craft structural design. Show more

Keywords: Local slamming, structural loads, high-speed craft, experiments, finite element modeling

DOI: 10.3233/ISP-130104

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 17-39, 2014

Authors: Rashkovskiy, S.A. | Rashkovskyi, A.S.

Article Type: Research Article

Abstract: There are three principal methods of launching a new ship including gravitational launching, floating-out launching and mechanical launching. A launching with marine airbags is a new kind of gravitational launching; it allows launching the ships which DWT is below 60,000 tonnes. In this paper we consider the ship launching by using marine airbags. The main principle of airbag ship launching is based on changing the force of sliding friction into rolling friction. One of the important characteristics of such devices is resistance force which occurs during airbag rolling under the compressive load. This force can be named rolling friction, however …we show that the mechanism of the resistance force during airbag rolling, is fundamentally different from the well-known mechanism of rolling friction which occurs during rolling of the solid deformable body. We show that the rolling friction coefficient of airbags and ground depends on the ground situation and airbag bearing forces. We determine the marine airbag shape and three components of the force of rolling friction depending on geometric parameters and values of pulling and compressive forces. We show that the main component of this force is related to appearance of bending moments in the airbag shell during its rolling. We have shown that coefficient of rolling friction as a function of compressive force has a minimum after which it slightly depends on compressive force. The method of calculating the motion of a ship in case of ship launching from the longitudinal inclined slipway by using marine airbags is discussed. Show more

Keywords: Ship launching, longitudinal inclined slipway, marine airbags, rolling resistance

DOI: 10.3233/ISP-130105

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 41-59, 2014

Authors: Guan, Guan | Lin, Yan | Ji, Zhuoshang

Article Type: Research Article

Abstract: Currently, the bottom-up approach for subdivision is applied in shipyards. That is, a compartment of a ship is generated by modeling all compartments one by one. However, this method requires much time and efforts as the ship consists of compartments of several tens to several hundreds. To solve this problem, a new parametric subdivision method of the top-down approach is proposed in this study. The proposed method is based on space subdivision as if we cut a watermelon into many small pieces. For this, several parameters (bulkhead and inner knuckle positions) are set to generate the subdivision polyhedrons to split …the hull. Non-manifold modeling and its Boolean operations are applied. As a result, this method reduces the complexity of subdivision and visually reflects the designer's idea. It is proved that the subdivision and the calculation of hold capacities can be finished rapidly by this method, which lays the foundation for 3D parametric design of ship. Show more

Keywords: Quick subdivision, parametric, top-down approach, non-manifold, hold capacity

DOI: 10.3233/ISP-130106

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 61-79, 2014

Authors: Papanikolaou, A. | Boulougouris, E. | Sklavenitis, A.

Article Type: Research Article

Abstract: On December 8, 1966 the Ro–Pax ferry SS Heraklion capsized and sank in the Aegean Sea, resulting in the death of over 200 people. The present paper tries to shed some light into the various events that led to the largest tragedy of modern Greek maritime history. It re-constructs the accidental data based on a variety of original investigation reports, ship files and legal evidence. Ship's loading, intact and damage stability behaviour were re-investigated and the flooding/sinking of the ship was simulated by use of a time simulation method. Results of our investigation were compared with available testimonies of survivors. …It was found that downflooding of large void spaces below the flooded car deck and the effect of multiple free surfaces on ship's stability was eventually the main reason for SS Heraklion's capsize. Show more

Keywords: SS Heraklion, marine accident, damage stability, water on deck, extreme weather, sail-out permit, time simulation

DOI: 10.3233/ISP-130109

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 81-102, 2014

Authors: Sánchez-Caja, A. | González-Adalid, J. | Pérez-Sobrino, M. | Saisto, I.

Article Type: Research Article

Abstract: Systematic variations of the endplate geometry for two endplate propellers are made in order to assess the impact of the blade tip shape on propeller performance. Several types of modifications are analyzed including variations in plate width, contraction angle, plate sweep and flap angle. The effect of endplate geometry modifications in the radial distribution of circulation is illustrated. The magnitude of the circulation is derived from the analysis of the tangential velocities behind the propeller. The contribution of pressure and friction components to the total endplate forces is also shown. Comparisons are made at full scale. A special procedure for …the generation of the computational grids is implemented in order to minimize computational errors in the comparison of the alternative geometries. RANS code FINFLO is used in the evaluation. Show more

Keywords: Tip loaded propeller, CLT, endplate, RANS, circulation, FINFLO, efficiency

DOI: 10.3233/ISP-130107

Citation: International Shipbuilding Progress, vol. 61, no. 1-2, pp. 103-128, 2014