Ship Hull Research Articles

Investigation of the quality of the frame surface when modeling the hull of a vessel depending on the type of frame lines in the Compass 3D CAD

The article provides a brief overview of the CAD systems used in the field of shipbuilding. The potential possibilities of using the domestic computer-aided design system COMPASS 3D in shipbuilding in the task of three-dimensional modeling of the theoretical surface of the hull are shown. The methods of modeling the surface of the ship's hull using the Compass 3D CAD in the form of a frame surface, in which the shaping sections are various types of vessel contours: frames, buttocks and lines. A method for checking the simulated frame surface using control sections is proposed. A comparative analysis of the quality of surfaces obtained by different methods of its formation has been carried out according to a number of proposed quantitative indicators characterizing the smoothness and accuracy of the surface. The influence of the introduction of intermediate sections into the frame set on the quality indicators of the frame surface is analyzed. The results of a quantitative comparative analysis of the quality of the frame surface depending on the type of frame lines are presented. It has been shown that an increase in the total number of forming lines in the frame does not necessarily lead to an increase in the quality of the simulated surface. The results of the work may be of practical interest in the tasks of modeling and evaluating the quality of frame surfaces for various purposes, set by a set of sections in various planes, and will also help in choosing an automated design system for shipbuilding enterprises.

Synthesis of a dynamic positioning algorithm for wheeled boats

The work analyzes the controllability indicators of a vessel with a wheeled propulsion-steering complex and an azimuth thruster in order to identify the possibility of developing high-precision control algorithms, such as the dynamic positioning task. The influence of the parameters of the wheel-propulsion steering complex and the azimuth thruster on the dynamics of the vessel is considered, and the areas of controllability of the vessel are identified for various propulsion parameters. The influence on the dynamics of the vessel of external wind influence, which has a great influence on the dynamics of the vessel due to its design features (shallow draft, flat bottom, large windage), has been studied. The areas of controllability of the vessel under conditions of external influence when changing wind parameters (force and direction) and parameters of propulsors with separate and joint use of propulsors are determined. An algorithm has been synthesized for dynamically holding a vessel at a given point under wind influence while maintaining a given hull position. The dynamic positioning algorithm consists of two parallel processes. The first is the return of the center of mass of the vessel, which has shifted under the influence of external influences, to a given point due to the wheeled propulsion and steering complex. The second is maintaining a given orientation of the ship's hull using an azimuth thruster. Computer simulation confirmed the high quality indicators of the proposed control algorithm.

Artificial intelligence-based ship hull plate corrosion monitoring using Convolutional Neural Network (CNN): comparison of YOLOv8 and Detectron2 architecture models

ABSTRACT Detecting and monitoring structural damage is crucial to prevent significant damage to ship structures caused by corrosion. This study aims to measure the performance of corrosion detection using Convolutional Neural Networks (CNN) by comparing YOLOv8 and Detectron2 models analyzed at various data augmentation settings. The results show that Detectron2 with the ResNet101 backbone performs better than Detectron2 ResNet50 and YOLOv8 models. The result found that applied augmentation data settings, such as vertical & horizontal flip, rotation, and increasing & decreasing colour saturation, highlight their importance in training robust corrosion detection models. These findings contribute to developing corrosion detection methods, showing that the Detectron2 model with instance segmentation can overcome the complexity and variety of corrosion shapes more effectively than YOLOv8 model. The instance segmentation model has proven to be the more effective CNN model for detecting abstract objects, such as corrosion damage in ship hulls.

Numerical Investigation of Low-Velocity Ice Impact on a Composite Ship Hull Using an FEM/SPH Formulation

Numerical Investigation of Low-Velocity Ice Impact on a Composite Ship Hull Using an FEM/SPH Formulation

An improved similarity method for stiffened plates subjected to combined loads of longitudinal compression and lateral pressure

Structures’ ultimate strength has been increasingly valued in the past few decades. The model test is an important and reliable way to estimate the ultimate strength. For large and complex structures, like ship hull structures, the test subject is usually scale models due to the limitation of loading capacity and space of laboratories. Therefore, the similarity method and the design of scale models are of great importance. The stiffened plate is the minimum unit that makes up thin-walled structures. The similarity method of the ultimate strength of stiffened plates is the base of the similarity method of large and complex structures. This paper is a further study of an existing similarity method proposed in our previous work. A stiffened plate from a real ship is taken as the subject. 22 combinations of scale ratios are used to design scale models. The 23 models (including the original model) are subjected to a combined load of longitudinal compression and lateral pressure. The non-linear finite element method is used to analyze these models. The results revealed that the previous method is only suitable for scale models with small degrees of geometrical distortion. It didn't consider the effect of geometrical distortions. An improved similarity method and scale model design method are proposed to solve these problems. The improved methods consider the geometrical distortion of scale models and are applicable to more geometrically distorted scale models. More numerical examples are performed to verify the correctness and advantage of the improved methods.

Research progress on intelligent optimization techniques for energy-efficient design of ship hull forms

Research progress on intelligent optimization techniques for energy-efficient design of ship hull forms

Fiberglass Construction Testing Simulation On Boat Hulls

As a maritime country, Indonesia relies heavily on ships as an economical means of transportation and conveyance. Boats, which were used for many years, were originally made of wood. However, because wood has properties that are easily weathered due to weather and chemical factors and requires adequate maintenance, fiberglass material in the form of FRP (Fiber Reinforced Plastics) laminates appeared as a substitute for wood. This material has many advantages over wood, so ships made from FRP began to gain a place in the shipping world, especially among ship manufacturers. However, In 2009, a survey carried out at multiple shipyards revealed that the construction design and lamination process of fiberglass ship hulls generally did not have clear standards, resulting in a significant risk of accidents. To minimize this risk, a simulation of fiberglass construction testing was held with samples taken from 6 shipyards where each sample had a different configuration and material, and the results of Carbon Fiber provided optimal results.

Developing a predictive method based on the vibration behavior of a naval ship hull model using hybrid fuzzy meta-heuristic algorithms

Ships are complex structures composed of various components with exclusive dynamic behaviors and natural frequencies, so assessing their vibration behavior is essential. Some situations in practical applications could alter the ship's dynamic characteristics and cause significant changes in its vibration behavior. Since the ship's mass is one of the most important dynamic parameters in determining vibration behavior, local mass change can lead to changes in its dynamic characteristics and must be considered. This study aims to develop a method to predict the effect of the location and magnitude of mass change on the ship hull's vibration behavior. It would be feasible to enhance the dynamic behavior and reduce undesirable noises by locating the mass change on the ship hull. In this regard, experimental and numerical modal analysis is performed on a scaled model of a naval ship hull. The baseline FE model is used to calculate the variation in frequencies of the model caused by different local mass change scenarios. Using these measurements a fuzzy system is generated and optimized by Genetic and Particle Swarm Optimization algorithms. Finally, the efficiency of the fuzzy-PSO is validated by different mass change scenarios foreseen on the physical model of the ship hull.

Evaluation of operational parameters for vessel's flexible subsea pipelines

AbstractThe operation of offshore vessels is directly related to the use of flexible pipelines. The article describes in detail the analysis of power, geometric, kinematic and technological parameters that affect the main operational characteristics of these pipes during their operation under water, in rough sea conditions and under wind loads. The article describes the degree of dependence between loads on the pipeline and velocity of the oncoming flow, the geometry of the pipe and the distance to the rigid surface of the ship's hull or the seabed. It was determined how the flow velocity during parametric oscillations of the pipeline in unrestricted flow and near the surface of the seabed affects the change in its drag and lift coefficients. An estimate of operational limits of flexible pipeline instability was obtained. On the base of changes in distributed load, specific values for safe lengths of pipelines were formulated. It has been stated that the probability of failure‐free operation of a flexible pipeline at a level of 0.99 is directly determined by the frequency of its oscillation. Its numerical values should always be at a level that does not exceed 3.7% of the frequency of pipe dynamic oscillations.

A pointwise weighting prediction variance–high-dimensional model representation model-based global optimization approach for ship hull parametric design

Ship hull optimization techniques based on computer-aided design/computational fluid dynamics can effectively enhance the efficiency and stability of ship designs, with significant application prospects. To enhance the potential of ship hull optimization, increasing design variable dimensionality is essential, but can cause a significant increase in hydrodynamic simulations. To reduce simulations required for high-dimensional ship hull optimization, a new surrogate method, pointwise weighting prediction variance–high-dimensional model representation (PWPV-HDMR), which uses pointwise weighting prediction variance (PWPV) to aggregate different a priori assumptions, is developed. Moreover, a differential evolution algorithm is used to identify promising hull design parameters, using the PWPV-HDMR model instead of costly simulation as the fitness function. The proposed approach is tested on the hydrostatic resistance optimization of KRISO Container Ship. The results show that PWPV-HDMR outperforms kriging-HDMR, with a better resistance optimization effect, illustrating the effectiveness of the PWPV-HDMR-based global optimization approach in discovering promising ship hull parameters.

Cutting failure behavior of foam core sandwich plates

During the ship, collisions with reefs or grounding may cause damage to the hull of ships made of sandwich plates. The cutting failure mechanism of sandwich panels is still not fully understood. In this paper, the failure behavior of metal foam sandwich plates under cutting load by a wedge-shaped indenter is studied through analytical, experimental, and numerical methods. An analytical model is proposed to describe the cutting failure behavior of foam core sandwich plates. Based on experimental results, three distinct failure modes of foam sandwich plates with varying thicknesses are observed. Numerical simulations are performed, and analytical and numerical results capture experimental results reasonably. The effects of core thickness, face-sheet thickness, and tip angle and cutting angle of wedge indenter on the failure mode, load-carrying capacity and energy absorption performance of the sandwich plates are explored. The present analytical model can effectively predict the cutting failure behavior of sandwich plates.

Power Generation Optimization for Next-Generation Cruise Ships with MVDC Architecture: A Dynamic Modeling and Simulation Approach

The cruise industry is obliged by economic and environmental initiatives to pursue fuel-efficient solutions and lower ship exhaust emissions. The medium voltage DC (MVDC) distribution with intelligent power management has become a concept for next-generation onboard power systems as its energy-saving feature is to eliminate the frequency constraint and simultaneously optimize engine loads and speed in response to load variations. The incentive for this transition lies on one hand in the fuel efficiency consideration and the reduction of power losses from serial conversion stages. On the other hand, the DC-based technology has been conceived as high-power density design, thus significantly increasing the payload. This study investigates such potential benefits focusing exclusively on large cruise vessels. A highly representative model of the integrated power platform that incorporates all dynamic interactions from the ship hull and essential machinery typically installed on board cruise ships is proposed. The power management strategy also takes account of actual sea conditions and real-time operation requirements. The simulation results demonstrate that the optimization-based MVDC system is able to maximize the opportunity of search agents in finding optimum fuel efficiency areas throughout the scenario time. An analysis of the system structure weight and space reduction of the MVDC architecture is also performed through the utilization of more compact electrical distribution devices and very high power-dense combustion turbines.

The influence of welding-induced 3D residual stress and distortion on the ultimate strength of multi-stiffened thin plate structures under cyclic load

Stiffened thin plates made of high-strength steel are widely employed in ship hull structures. Their strength capacity is highly sensitive to the welding imperfections and potential extreme cyclic loading from harsh sea state. In this work, a thermal elasto-plastic finite element analysis is conducted to simulate the 3D distribution of welding-induced residual stress and distortion of stiffened thin plate structures with triple spans and triple bays varying the plate thickness and heat input. Experimental results provided by other scholars are used to validate the welding simulation. Afterwards, the ultimate strength and collapse behaviour of the welded structures under different load patterns are dealt with, including monotonic compression load, cyclic compression-tension load and cyclic compression load. Observation from numerical results indicates that, in general, the compressive strength is reduced in each considered cycle by the residual stress as the amplitude of cyclic compression-tension load approximates to the ultimate compressive strain. When this parameter is much greater than the ultimate compressive strain or the stiffened plate is subjected to cyclic compression load, the reduction in ultimate strength is significant in the first cycle, whereas the reduction is ignorable in the later cycles. Besides, if the buckling mode of initial deflection with antisymmetric configuration is superposed to the symmetric out-of-plane welding distortion, impact of the residual stress will be diminished as the asymmetry becomes notable.

A vision measurement method for ship hull plates based on multi-view stereo and image segmentation

The background denoising of point clouds is challenging for the measurement of ship hull plates. To address this issue, a vision measurement method is proposed by combining an identity cost volume network (ICV-Net) and a segment anything model (SAM). By applying the ship hull plate masks segmented by SAM to the corresponding depth maps inferred by ICV-Net, the background noise can be directly removed at the depth map level. Additionally, an edge extraction optimization algorithm complementary to SAM is proposed to eliminate the thickness-related noise. Moreover, an efficient depth map refinement algorithm is proposed by imposing the smoothness prior of ship hull plate surfaces and multi-view photometric consistency. Sub-pixel accurate depth maps of ship hull plates can be obtained by the depth map refinement. Experimental results suggest that the proposed method can automatically, accurately and efficiently remove the background noise of ship hull plates, which is crucial toward practical application.

Detection of Flaws in Ship Hull Using Underwater Remotely Operated Vehicle

Detection of Flaws in Ship Hull Using Underwater Remotely Operated Vehicle

Effects of adverse sea conditions on the dynamic performance of a cruise ship integrated power system

In adverse sea conditions, changes in the propeller emergence depth can cause propulsion load fluctuations, resulting in significant variations in ship-integrated power systems (IPS). These fluctuations can severely affect the power quality of ships and the operational efficiency of electrical devices. To develop appropriate mitigation measures against the impact of wind and waves on IPS, a comprehensive model that can simulate the response characteristics of the hull and IPS for different heading angles in different sea conditions is necessary. This paper presents an integrated multi-system dynamic model capable of simulating the response characteristics of a ship's hull and its IPS under the wind and waves interference. A novel method is proposed to estimate propeller thrust and torque loss directly from the ship's pitch and roll angles. Utilizing this dynamic model, the responses characteristics of the hull and IPS in varying sea conditions have been investigated. The findings demonstrate that the model accurately captures variations in ship motions, as well as IPS voltage and frequency, under wind and waves interference. Additionally, this study explores the application of a hybrid energy storage system (HESS) to enhance the IPS power quality in the context of Sea State (SS) 7. Results indicate that the HESS has good potential to compensate for propulsion load fluctuations, thereby mitigating the negative impacts on the ship's IPS.

First-principles algorithms for ship motion simulation based on ARMA and trochoidal wave models

An approach for the direct simulation of ship behavior in heavy sea conditions using modern computers methods is described. The approach includes a model for wind-driven waves, algorithms for hydrodynamic pressure calculation, a solution of the diffraction problem, and the integration of the approach into a problem solution environment. An ARMA (autoregressive-moving average) model is used for the simulation of a hydrodynamically adequate spatial-temporal wave surface and integrated with a calculation of hydrodynamic pressure at any point under the wave surface. The integration of the wave pressure over the ship hull and the solution of the diffraction problem provides the excitation forces and moments and permits direct numerical simulation of ship motions in waves. An effective numerical implementation of the algorithms with mapping to modern computer architecture is described. The combination of the numerical algorithms with a visual simulation environment is presented as a virtual testbed.

A framework to analyse the probability of accidental hull girder failure considering advanced corrosion degradation for risk-based ship design

Ship’s hull girder failure could result from maritime accident that can cause human life loss, environmental disaster, and major economic impacts. In risk-based ship design paradigm, accounting for rare phenomena (e.g. ship-ship collision or grounding) is important to provide safe and durable structure. In-service corrosion-induced hull degradation should be considered at the design stage, as it can significantly affect structural strength. The current study presents a novel framework to estimate the probability of ship hull girder failure, accounting for novel corrosion modelling techniques and accidental damage. The associated uncertainties are considered using statistical sampling from evidence-based distributions. A state-of-the-art deterministic model for ultimate strength calculation is applied using Monte Carlo simulation approach, resulting in the probability of hull failure through a reliability assessment. Wave and still-water bending moments are considered random variables. Two case studies of tanker ships with varying sizes are executed to show the applicability of the proposed framework. The results indicate that proper consideration of corrosion is of high importance, as ageing can significantly increase the probability of failure if accidental damage happens. Therefore, whereas future research and model refinement are discussed, the presented framework can serve for risk-based ship design tool and assess existing structures’ safety.

Comparison Of Full-Scale PIV Measurements With CFD Simulations Of A Ship Propeller Inflow

Flow around the ship's hull and specifically the inflow conditions of the propeller(s) critically influence the propeller efficiency and cavitation behaviour. In a typical single-propeller vessel, the hull of the ship creates a velocity deficit in the top part of the propeller disk. This creates suitable conditions for cavitation, which is the main source of noise and vibration both inside the vessel as well as in the marine environment. Recently, two measurement campaigns were performed using a novel full-scale stereo-PIV device built to measure flows around vessels sailing at sea. During the first campaign, performed in one of MARIN's basins, the device was commissioned. The second campaign was performed during a sea trial; it resulted in propeller inflow data that can be used for validating CFD codes. The uncertainty of the PIV measurements was assessed using both campaigns. In the basin, uncertainty bias could be determined by comparing the PIV results with the carriage speed. At sea, the random part of uncertainty was determined by quantifying the standard deviation of the mean velocity for all three velocity components in the wake peak area of the propeller inflow. Overall, the uncertainty was found to be acceptably small, given the scale of the measurement and the necessity to work with naturally occurring seeding particles in the sea. CFD calculations of the same full-scale flow were performed using an in-house flow solver. The CFD results predicted the propeller RPM and the delivered power measured during the full-scale trial well, which gives confidence in the ability of CFD to predict ship trial performance. The comparison of the flow fields was good, with the PIV results demonstrating that full-scale PIV can be done reliably, and that the CFD is able to capture the major features of the flow in the considered area. For a large part of the flow field, the CFD was within the measurement uncertainty band. The wake peak was slightly underpredicted, which may be related to roughness effects on the boundary layer thickness.

A two-way coupled fluid–structure interaction method for predicting the slamming loads and structural responses on a stiffened wedge

Ships navigating through rough seas are subjected to slamming loads from waves, which can lead to structural damage and maritime accidents. The wedge model is commonly employed to investigate slamming loads and structural responses. While a stiffened wedge closely resembles a real ship hull plate, incorporating it into fluid–structure interaction simulations presents challenges. This paper proposes a two-way coupled fluid–structure interaction method to examine slamming loads and structural responses of a free fall non-prismatic stiffened steel wedge. Hydrodynamic loads are determined through Reynolds-averaged Navier–Stokes computations using OpenFOAM, while structural responses are predicted using the finite element analysis (FEA) software Calculix. To achieve two-way coupling between computational fluid dynamics and FEA simulations, a coupling library for partitioned multi-physics simulations, preCICE, is introduced. The computed impact pressure and stress align well with available experimental data. Various free fall heights are investigated in the numerical simulations. The results indicate that elastic deformation mitigates impact pressure, while the presence of transverse ribs enhances the rigidity of the flexible plate. The duration of pressure and the peak slamming pressure exhibit an inverse correlation. Greater free fall heights result in shorter pressure duration times, and smaller free fall heights may reduce rise time. Three-dimensional effects cause pressure to decrease along the midpoint of the plate toward both sides. Additionally, structural stress in the central area exceeds that in the areas on both sides at the same height. In conclusion, the proposed two-way coupled model proves suitable for accurately and efficiently computing hydroelastic slamming on flexible wedges.