Hull Shell Research Articles

Investigation on Calm Water Resistance of Wind Turbine Installation Vessels with a Type of T-BOW

Given the typical characteristics of self-propulsion and jack-up wind turbine installation vessels (WTIVs), including their full and blunt hull form and complex appendages, this paper combines the model test method with the RANS-based CFD numerical prediction method to experimentally and numerically study the resistance of the optimized hull at different spudcan retraction positions. The calm water resistance components and their mechanisms of WTIVs based on T-BOW were obtained. Furthermore, using the multivariate nonlinear least squares method, an empirical formula for rapid resistance estimation based on the Holtrop method was derived, and its prediction accuracy and applicability were validated with a full-scale ship case. This study indicates that the primary resistance components of such low-speed vessels are viscous pressure resistance, followed by frictional resistance and wave-making resistance. Notably, the spudcan retraction well area, as a unique appendage of WTIVs, exhibits a significant “moonpool additional resistance” effect. Different spudcan retraction positions affect the total calm water resistance by approximately 20% to 30%. Therefore, in the resistance optimization design of WTIVs, special attention should be paid to the matching design of the spudcan structure and the hull shell plate lines in the spudcan retraction well area.

A Framework for Structural Analysis of Icebreakers during Ramming of First-Year Ice Ridges

This paper presents a framework for structural analysis of icebreakers during ramming of first-year ice ridges. The framework links the ice-ridge load and the structural analysis based on the physical characteristics of ship–ice-ridge interactions. A ship–ice-ridge interaction study was conducted to demonstrate the feasibility of the proposed framework. A PC-2 icebreaker was chosen for the ship–ice interaction study, and the geometrical and physical properties of the ice ridge were determined based on empirical data. The ice ridge was modeled by solid elements equipped with the continuous surface cap model (CSCM). To validate the approach, the simulated ice resistance was computed using the Lindqvist solution and in situ tests of R/V Xuelong 2. First, the local ice-induced pressure on the hull shell was determined based on numerical simulations. Subsequently, the local ice pressure was applied to local deformable sub-structural models of the PC-2 icebreaker hull by means of triangular impulse loads. Finally, the structural response of sub-structural models with refined meshes was computed. This case study demonstrates that the proposed framework is suitable for structural analysis of ice-induced stresses in local hull components. The results show that the ice load and the structural response obtained based on the four first-year ice-ridge models show obvious differences. Furthermore, the ice load and corresponding structural response increases with the width of the ridge and with increasing ship speed.

Автоматизация моделирования поверхности судового корпуса

The article presents a modified algorithm for automated formation of geometric model of ship hull surface. The use of developed algorithm for construction of NURBS-surfaces allows to decrease labor input in several times in comparison with the use of manual labor when modeling surfaces in standard shipbuilding modeling systems like Sea Solution, Rhino and others. On the basis of this algorithm a software application is created, implemented in HTML5, JavaScript. The application allows to solve problems of creating and displaying three-dimensional models of ship surfaces in a standard the Internet browser. The program allows you to quickly analyze variants of the geometry of the ship hull model by adjusting the initial data, which significantly increases the productivity of the designer. It is possible to export the formed NURBS-surface for use in other design systems, including ship hull construction modeling, stability calculations, hull shell cutting and other tasks.

Design and Cost Multi-Objective Optimization of Small-Scale LNG Carriers using the Value Engineering Approach

Nowadays, liquefied natural gas (LNG) carriers are the main merchant fleets for the transport of natural gas for energy. The large LNG carrier has a more efficient freight cost (approximately 7.8 USD/MMBTU) than a small-scale LNG carrier (SSLNGC; approx. 12,8 USD/MMBTU). Another method must be introduced to make SSLNGCs more cost-efficient. As such, this work conducted an experiment to improve the design of SSLNGCs via design and cost optimization by combining a value engineering approach and multi-objective optimization to decrease hull resistance and lower construction material costs by adjusting the ship dimension ratio. By improving the conceptual design and using semi-integrated numerical simulations, the final result showed improvements in SSLNGCs by decreasing the hull shell area by 1.57% to reduce the construction material needed and total ship resistance by 8.3%.

Application of the environmentally safe operating schemes to the cooling systems of ship power plant

The possibility of using the ecologically safe operation on a closed-loop circuit instead of an open-loop cooling system is considered. For this purpose, it was proposed to use the ballast tanks on the ship. To ensure effective heat removal, it is proposed to apply a jet inlet of coolant to the hull shell of a ship. The flow regimes of the impact fluid jet were visualized. The critical Reynolds number is determined. Heat transfer coefficients and generalizing calculation dependences are determined by experiments.

3D Simulation of Large Hull Shell Surface based on 3D Digital Video

ABSTRACT Zhong, J., 2019. 3D simulation of large hull shell surface based on 3D digital video. In: Hoang, A.T. and Aqeel Ashraf, M. (eds.), Research, Monitoring, and Engineering of Coastal, Port, a...

Modelling the destruction process of a thermal reactor by man-made space debris impact

The three-dimensional transient problem of the interaction of artificial space debris particles (steel bolt M12) with a spacecraft model reactor is solved. Two cases of interaction are considered, the first is the reactor filled with water, and the second is the empty reactor. The calculations show that the impact of a high-speed steel bolt on the reactor with water at a speed of 11.17 m/s leads to the reactor failure. A water-free reactor obtains catastrophic damage to the hull shell and fuel cells.

Vibration analysis of a submarine elastic propeller-shaft-hull system using FRF-based substructuring method

A dynamic model to study the coupled longitudinal and transverse vibrations of a submarine elastic propeller-shaft-hull system is developed using the FRF-based substructuring method (FBSM). The total system is firstly modeled as two substructures: the elastic propeller-shaft subsystem and the hull shell. For the former substructure, the elastic propeller is modeled by using harmonic blade array elements and the shafts are assumed to be Timoshenko beams, while the latter one is modeled using traditional finite element method. After that, the two substructures are synthesized using FBSM. The modes, the natural frequencies and the coupled longitudinal and transverse vibration characteristics of the propeller-shaft subsystem, the hull shell, and the total system are analyzed. An experiment studying the dynamic characteristics of a large-scale submarine experimental setup is processed and compared with the numerical results, which shows great consistency. Finally, a further discussion is carried out focused on how the bearing stiffness affects the coupled vibration characteristics of the total system.

Laser Doppler Vibrometer Based Examination of the Efficiency of Introducing Artificial Delaminations into Composite Shells

Abstract During its operation, the laminate shell of the watercraft hull can be exposed to local stability losses caused by the appearance and development of delaminations. The sources of these delaminations are discontinuities, created both in the production process and as a result of bumps of foreign bodies into the hull in operation. In the environment of fatigue loads acting on the hull, the delaminations propagate and lead to the loss of load capacity of the hull structure. There is a need to improve diagnostic systems used in Structural Health Monitoring (SHM) of laminate hull elements to detect and monitor the development of the delaminations. Effective diagnostic systems used for delamination assessment base on expert systems. Along with other tools, the expert diagnostic advisory systems make use of the non-destructive examination method which consists in generating elastic waves in the hull shell structure and observing their changes by comparing the recorded signal with damage patterns collected in the expert system database. This system requires introducing certain patterns to its knowledge base, based on the results of experimental examinations performed on specimens with implemented artificial delaminations. The article presents the results of the examination oriented on assessing the delaminations artificially generated in the structure of glass- and carbon-epoxy laminates by introducing local non-adhesive layers with the aid of thin polyethylene film, teflon insert, or thin layer of polyvinyl alcohol. The efficiency of each method was assessed using laser vibrometry. The effect of the depth of delamination position in the laminate on the efficiency of the applied method is documented as well.

An high order Mixed Interpolation Tensorial Components (MITC) shell element approach for modeling the buckling behavior of delaminated composites

This paper describes the experimental and numerical studies carried out on delaminated fiberglass epoxy resin laminates made-up by different fabrication methods, namely by vacuum infusion and prepreg. While the tested specimens were originally intended for the assessment of buckling behavior of composite laminates of wind turbine blades, results were found valuable for the marine industry as well, because similar laminates are used for the hull shell and stiffeners. Systematic calculations were carried out to assess the effects of an embedded delamination on the buckling load, varying the size and through thickness position of the delamination. Different finite element modeling strategies were considered and validated against the experimental results. The one applying the 9 nodes MITC shell elements was found matching the experimental data despite failure modes were different for the two fabrication methods.

An analytical/numerical study on buckling behaviour of typical composite top hat stiffened panels

This paper deals with the buckling strength of typical ship stiffened panels built in fibreglass composite laminates. The results obtained applying analytical formulations based on equilibrium and potential energy equations are compared with the ones obtained by linearised eigenvalue analyses of rather detailed finite-element models. Analytical formulations consider an elementary panel only, accounting for the boundary effects of stiffeners surrounding its edges, while FE models fully describe the interactions among plate and stiffeners as a whole. A sensitivity analysis to highlight the most influencing parameters in the problem is also presented. So far no systematic scantling assessment of buckling behaviour of hull shell and deck panels seems to be recommended by classification societies’ rules for pleasure crafts made in composite materials. Thus, this paper aims at illustrating the application limits of analytical methods, natural candidates to become the basis of rule requirements. Difficulties in the evaluation of torsion behaviour of stiffeners and of corresponding buckling modes involving both the plate and the stiffeners are highlighted. Some concluding suggestions for rule scantling assessment formulations are eventually provided.

Optimum design of filament-wound multilayer-sandwich submersible pressure hulls

Submersible pressure hulls with fiber-reinforced multilayer-sandwich constructions have been developed in recent years as substitutes for classical metallic ring-stiffened pressure hulls. This study aims to optimize the design of filament-wound multilayer-sandwich submersible pressure hulls, taking into consideration the shell buckling strength constraint, the angle-ply laminated facing failure strength constraint and the low-density isotropic core yielding strength constraint under hydrostatic pressure using the hybrid genetic algorithm (HGA). The thickness of the facing, the thickness of the core layer, the orientation angle of the fibers in the facings and the shear modulus of the core material are taken as design variables. A sensitivity analysis is performed to study the effects of the operational depths and the hull shell geometry parameter, the length-to-diameter ratio (L/D), on the optimal design of filament-wound multilayer-sandwich submersible pressure hulls with graphite/epoxy, glass/epoxy and boron/epoxy composite facings. The results reveal that the optimal weight of various sandwich pressure hulls increases linearly with the operational depth, but it is almost unchanged as the geometry paramter. Furthermore, Graphite/Epoxy is the best choice for the material of the facings in a light-weight design. With reference to wall design, Boron/Epoxy is the best choice for the material of the facing at shallow depths, but Graphite/Epoxy is the best choice at extreme depths. Results of this study provide a valuable reference for designers of underwater vehicles.

Damage Tolerance and Repair of GFRP Warships

The United Kingdom has operated glass-fiber-reinforced plastic (GFRP) minesweeper vessels since the early 1970s. Under typical operating conditions they may sustain minor impact damage, leading to delaminations within the hull shell and debonding of the stiffener frames. Such damage is costly to repair, and hence there has been a move towards cost reduction through better understanding of the structural behavior of typical defects under the loading conditions present within the structure. This approach, using damage tolerance techniques, has led to a relaxation in the requirement for repair, and consequently the number of repairs has been substantially reduced. In addition, advance techniques have been developed using resin infusion technology for the re-attachment of debonded stiffener frames. The structural element tests used to validate the damage tolerance philosophy will be examined and the resin-infusion repair method explained using a case study detailing its first successful application.

Statistics of ship plating distortions

The paper contains the results of many years of measurements of post-welding distortions of ship hull shell plating. Altogether 1998 plates of general cargo ships, multi-purpose tugs, bulk carriers, chemical carriers, tankers, research vessels as well as passenger/cargo ferries were examined. The deadweight of the ships investigated was within the range of 1300 and 33 350 tons. Results of statistical and regression analyses of the measurements are presented together with a brief description of the measurement technique.

Noise control in boats and small ships

Noise-control problems in boats and small ships are shown to differ from those of other ship classes due to geometrical scaling laws for person occupied spaces, and by high power to displacement ratios common to them. For the fastest boats, noise sources from propeller cavitation, flow, and spray noise have pronounced importance. Obstacles to noise-reduction techniques outlined are sensitivity of boat performance to weight, expected seaway induced acceleration loads, and corrosive effects of salt environment. Criteria for noise control are presented based on ship function: pleasure/work and continuous running/intermittent operation. Examples illustrating the general problem include measured machinery foundation impedance and vibration mount effectiveness, measured transfer functions for structure-borne noise. Examples of noise-control techniques include measured results with lightweight joiner-work partitions, isolation of interior trim from hull shell, and successful use of structural damping materials.