Ship Design Stage Research Articles

Numerical Investigation on a High-Speed Transom Stern Ship Advancing in Shallow Water

A high-speed advancing ship will cause significant squats in shallow water, which could increase the risk of grounding. To this end, a program based on the Rankine higher-order boundary element method (HOBEM) is developed to investigate a high-speed displacement ship with a transom stern moving in shallow water. The nonlinear free surface condition is satisfied by adopting an iterative algorithm on the real free surface. The transom condition is considered by implementing a modified transom condition. Computations of wave-making resistance, sinkage and trim in deep water are first performed, and satisfactory agreement is achieved by comparing with the experimental results; the simulations are then extended to the shallow water case. It indicates that the present method can provide a suitable balance of practicability and robustness, which can be considered as an efficient tool for the guidance in ship design stage.

Integrating Computational Fluid Dynamics for Maneuverability Prediction in Dual Full Rotary Propulsion Ships: A 4-DOF Mathematical Model Approach

To predict the maneuverability of a dual full rotary propulsion ship quickly and accurately, the integrated computational fluid dynamics (CFD) and mathematical model approach is performed to simulate the ship turning and zigzag tests, which are then compared and validated against a full-scale trial carried out under actual sea conditions. Initially, the RANS equations are solved, employing the Volume of Fluid (VOF) method to capture the free water surface, while a numerical simulation of the captive model test is conducted using the rigid body motion module. Secondly, hydrodynamic derivatives for the MMG model are obtained from the CFD simulations and empirical formula. Lastly, a four-degree-of-freedom mathematical model group (MMG) maneuvering model is proposed for the dual full rotary propulsion ship, incorporating full-scale simulations of turning and zigzag tests followed by a full-scale trial for comparative validation. The results indicate that the proposed method has a high accuracy in predicting the maneuverability of dual full-rotary propulsion ships, with an average error of less than 10% from the full-scale trial data (and within 5% for the tactical diameters in particular) in spite of the influence of environmental factors such as wind and waves. It provides experience in predicting the maneuverability of a full-scale ship during the ship design stage.

Prediction of Ship Main Particulars for Harbor Tugboats Using a Bayesian Network Model and Non-Linear Regression

Determining the key characteristics of a ship during the concept and preliminary design phases is a critical and intricate process. In this study, we propose an alternative to traditional empirical methods by introducing a model to estimate the main particulars of diesel-powered Z-Drive harbor tugboats. This prediction is performed to determine the main particulars of tugboats: length, beam, draft, and power concerning the required service speed and bollard pull values, employing Bayesian network and non-linear regression methods. We utilized a dataset comprising 476 samples from 68 distinct diesel-powered Z-Drive harbor tugboat series to construct this model. The case study results demonstrate that the established model accurately predicts the main parameters of a tugboat with the obtained average of mean absolute percentage error values; 6.574% for the Bayesian network and 5.795%, 9.955% for non-linear regression methods. This model, therefore, proves to be a practical and valuable tool for ship designers in determining the main particulars of ships during the concept design stage by reducing revision return possibilities in further stages of ship design.

Design of the electrical system on a general cargo ship with a length of 105,669 meters

This research investigates the incorporation of LED lights and the zonal cavity method in the initial design stage of a cargo-type ship, focusing on efficient lighting for diverse ship zones. The study aims to determine optimal lighting requirements, adhering to industry standards, for zones such as double bottom, maindeck, poopdeck, boatdeck, bridgedeck, navdeck, and emergency conditions. Ships play a vital role in transporting passengers and goods across seas and rivers, necessitating effective lighting systems for safe operations, particularly during nighttime. This paper explores the integration of LED lights and the zonal cavity method in the general arrangement design of a cargo ship. The zonal cavity method is applied to ascertain lighting intensity in different ship zones based on room dimensions, including width, height, length, and area. Illumination values are determined according to established standards for each zone. The cumulative lighting electricity load for various ship zones using LED lights is calculated to identify specific power requirements.The lighting power requirements for the double bottom, maindeck, poopdeck, boatdeck, bridgedeck, navdeck, and emergency conditions are found to be 0.141 KW, 0.75 KW, 1.068 KW, 0.762 KW, 0.671 KW, 0.42 KW, and 0.296 KW, respectively. The total lighting power for all zones is calculated as 3.7776 KW, suggesting the installation of a 4 KW generator for optimal power supply.The application of the zonal cavity method in the planning and design of a cargo ship's lighting system, combined with energy-efficient LED lights, proves to be an effective approach. The results indicate that a 4 KW generator is sufficient to meet the lighting power demands for various ship zones, ensuring compliance with safety standards and technological advancements in maritime lighting.

Verification of simplified underwater radiated noise estimation tool using Brown's formula

In recent years, the impact of underwater radiated noise from ships on marine life has attracted considerable global attention. Therefore, various research institutions are investigating this phenomenon through research and development efforts. In this study, authors have developed an underwater radiated noise estimation tool that can be used in the early stages of ship design. This tool calculates the underwater radiated noise level by applying Brown's formula, a simple estimation formula for predicting the noise generated by ships. The parameters required for Brown's formula are estimated using HOPE Light, a ship performance estimation software developed by the National Maritime Research Institute. The extent of cavitation is estimated using Burrill's diagram, a tool for assessing the occurrence of cavitation. The accuracy of the developed tool has been verified by comparing its results with full scale measurements of underwater radiated noise levels obtained off-board hydrophone array system.

Comparative analysis of closed-form expressions and other commonly used seakeeping methods

Closed-form expressions (CFE) are semi-analytical transfer functions for ship wave-induced responses based only on main ship particulars. They are useful in an early stage of ship design and situations when hull lines for seakeeping analysis are not available. As the accuracy of CFE remains an open subject, the aim of the present study is to quantify the frequency independent model error (FIME) of CFE. Measured transfer functions of the heave, pitch, and vertical wave bending moment at midship for 13 ships are acquired from literature, together with calculated transfer functions using the strip theory and the 3D panel method, where several speeds and heading angles are available. FIME is determined by comparing transfer functions calculated by CFE, strip theory, and 3D panel codes with model-scale experiments. Multivariate linear regression analysis is performed for three seakeeping methods to indicate a dependence of FIME on the main parameters of the analysis. Dispersion of the FIME around the regression line is determined, enabling a relative comparison of the uncertainty of seakeeping methods of different complexity. The results of this study may improve the practical applicability of CFE and provide an uncertainty quantification of commonly used seakeeping methods, which is important for probability-based applications.

The use of a set of artificial neural networks to predict added resistance in head waves at the parametric ship design stage

During the parametric ship design stage, added ship resistance, a component of total ship resistance is analysed to estimate the required propulsive power. The determination of added resistance at this design stage is problematic because the added resistance is calculated using hull shape, which is unknown at this stage. At the parametric design stage, only basic ship parameters, such as length, breadth, draught, block coefficient and Froude number are defined and known. Therefore, the focus of this research was to develop an effective tool to solve this problem. The article presents a set of five Artificial Neural Networks (ANNs) to predict added resistance using basic design parameters. Only model test data was used to train the ANNs in order to obtain reliable results. The research showed that using an ANN set consisting of five ANNs developed using different segregated data resulted in slightly more reliable and accurate estimates than using an individual ANN. To facilitate implementation, the developed ANNs were provided in the form of mathematical functions and open source software code from the Mendeley Data repository. A practical example of how an ANN set can be used to solve a design task was demonstrated in this article.

Establishment of a design study for comprehensive hydrodynamic optimisation in the preliminary stage of the ship design

ABSTRACT An automated practical multi-objective optimisation scheme is proposed for ship hull modification. A shift transformation and a self-blending method are sequentially performed based on resistance objectives at multi-design speeds. The Lackenby variation alters hull forms and produces initial designs. Subsequently, self-blending method combines obtained ships to cover design space. All processes are automated by MATLAB coding that connects the ©Maxsurf modeller and ©Maxsurf Resistance in the case of panel method resistance calculation. After whole shape optimisation, the platform defines ship portions in the stern and bow regions. Particularly, an approximation modelling Least-Square approach is investigated to construct a surrogate model. Optimisation results indicate 11.26% cost function reduction contributes to 16.23% resistance reduction at lower speed and 6.12% resistance reduction at higher speed for a passenger catamaran boat. Thus, the developed in-house optimisation code provides an optimal and cost-effective solution for hydrodynamic optimisation in the preliminary stage of ship design.

A semi analytic method for the analysis of the symmetric hydroelastic response of a container ship under slamming and green water loads

This paper presents a semi analytic time domain method for the analysis of the symmetric hydroelastic response of a container ship subject to slamming and green water loads. An Impulse Response Function (IRF) is adopted for the calculation of radiation, diffraction and wave excitation forces. Local hydrodynamic forces associated with green water on decks and slamming loads are respectively modelled by the Buchner’s Dam Break Model and a Generalised Wagner Model. The structural responses are captured by Euler-Bernoulli beam theory and solved by the modal superposition method. The Duhamel Integral technique is used to evaluate the dynamic response. A parametric study demonstrates how external forces may affect the global wave induced vertical bending moments and shear forces. Numerical simulations are compared against a hybrid method that combines computational fluid dynamics, boundary element and finite element methods for low to medium frequency induced dynamic response. It is concluded that the proposed semi analytic methodology is fast and accurate and may be useful at concept ship design stage.

Review of the Decision Support Methods Used in Optimizing Ship Hulls towards Improving Energy Efficiency

This paper presents a review of the different methods and techniques used to optimize ship hulls over the last six years (2017–2022). This review shows the different percentages of reduction in ship resistance, and thus in the fuel consumption, to improve ships’ energy efficiency, towards achieving the goal of maritime decarbonization. Operational research and machine learning are the common decision support methods and techniques used to find the optimal solution. This paper covers four research areas to improve ship hulls, including hull form, hull structure, hull cleaning and hull lubrication. In each area of research, several computer programs are used, depending on the study’s complexity and objective. It has been found that no specific method is considered the optimum, while the combination of several methods can achieve more accurate results. Most of the research work is focused on the concept stage of ship design, while research on operational conditions has recently taken place, achieving an improvement in energy efficiency. The finding of this study contributes to mapping the scientific knowledge of each technology used in ship hulls, identifying relevant topic areas, and recognizing research gaps and opportunities. It also helps to present holistic approaches in future research, supporting more realistic solutions towards sustainability.

Experimental and Numerical Predictions of Cryogenic Leakages in Welded Steel Plates

This study presented experimental and numerical research to investigate the effect of cryogenic leakage on a plate structure of AH36-grade steel containing welded joints. To simulate the cryogenic leakage conditions, the welded plate was exposed to a temperature of −196 °C by supplying liquid nitrogen (LN2) to the center of the steel plate. The time-dependent temperature history and strain variation were measured by using thermocouples and strain gauges attached to the plate surface. Additionally, the residual stress of the middle surface section before and after the cryogenic leakage process was measured by X-ray diffraction analysis (XRD). A three-dimensional finite element model was created with the use of a commercial finite element analysis (FEA) program to simulate the flux-cored arc welding process and cryogenic leakage process. The steel surface temperature dropped sharply and reached approximately −196 °C at 160 s after LN2 supplement. After the first 650 s of the LN2 leakage experiment, the outside of the trough reached approximately −75 °C and −25 °C, depending on the location of the thermal couples. Although there was a relative difference in the results, the experiment and numerical simulation results for temperature and stress distribution showed good agreement. The results could be utilized in the ship design stage adopting welded structures as a basic database.

Extent of damage analysis of naval ships subject to internal explosions

A well-balanced naval ship design to enhance the survivability from the initial design stage in parallel with other designs focusing on the major function and its inherent mission is considered as a desirable design trend in ROK navy since Cheonan sinking accident. Because it is difficult to estimate a hit location of a given threat for survivability evaluation, a statistical approach based on multiple-hit scenarios is frequently addressed, and it is necessary to accomplish rapid analyzes considering the tight design schedule. In addition, accurately estimating the extent of damage caused by the given threat is also an important matter to secure the reliability of evaluation. In particular, the empirical formula-based damage extent estimation method, which is frequently used for initial rapid vulnerability analysis, has limitations in not faithfully reflecting the latest technology advances such as hull design changes and diversification of threats, so researches on this have been continuously accomplished. In this study, a method for analyzing the extent of damage was developed considering the structural response of a ship to damage under a blast load. The proposed method quickly and easily calculates the extent of damage using physical design parameters together with the accurate analysis results and is also very effective at the initial design stage of the naval ship (e.g., in evaluating various design candidates for structural configurations). To show the effectiveness of suggested method, FLACS, a well-known commercial program for explosion analysis, is used for the analysis of nine representative scenarios together with the stepwise validations of the suggested procedure; the analysis results are observed the same in most cases with the developed program based on the proposed procedure, with a difference of approximately 15% for one scenario.

Hydrodynamic Decomposition-Based Optimization of Ship’s Hull–Propeller System Under Multiple Operating Conditions

_ In this research, a framework for the analysis and design optimization of ship hull–propeller systems (HPSs) in waves is developed. This framework can be utilized as an efficient synthesis tool to determine the main geometric characteristics of the HPSs during the early stage of ship design. The optimization is carried out in two levels and under multipoint operating conditions (OC). Multiobjective evolutionary algorithm based on decomposition (MOEA/D) as an efficient multiobjective evolutionary algorithm, Michell integral and OpenProp tool as low-fidelity hydrodynamic solvers and boundary element method (BEM) as medium-fidelity solver are applied on two case studies to minimize the effective power and maximize the propulsive efficiency of HPSs. To estimate the added wave resistance, an efficient semiempirical formula is also employed. The Series 60 hull form with DTMB P4118 single propeller and S175 hull form with KP505 twin-propeller are considered as the original models. The numerical results show that the framework can find optimized designs with better hydrodynamic performance. Introduction Optimizing the hydrodynamic performance of ships’ hull and propeller(s) based on multiple design condition has gained considerable importance over the last few years. High fuel oil costs are the reason that shipyards and ship owners are now focusing more than ever on the reduction of effective power and propulsive efficiency. Hydrodynamic performance parameters, such as effective power and propulsive efficiency, are determined by the hull form and propeller shape, so it is very important to choose a hull–propeller system (HPS) with good performance in early stage ship design. There exist two main factors in the hydrodynamic design optimization of marine systems. The first factor is simultaneously considering all components of the system influencing objective function(s) and the second one is selecting a less time-consuming solver with satisfactory accuracy. In the ship design process, these two factors must be taken for conducting a reasonable optimization into consideration.

Analysis of the impact of operation conditions on the bulk carriers design characteristics

The paper presents the results of a comparative analysis of the design characteristics of ships currently used for coal transporting from the ports of Far East of Russia to the Asia-Pacific countries with mathematical modeling and optimization results oriented to the economic criteria. The effectiveness and expediency of using ships in the certain directions of coal transportation is considered. The results of the analysis of the influence of operating conditions to the optimal values of the design characteristics (speed and payload capacity) and economic criteria of the functional efficiency of bulk carriers are given. The mathematical model for optimal values of the design characteristics of bulk carriers was used. The model takes into an account basic calculations of ship design and theory disciplines which are used at the initial stages of design. The calculations were made for the operating conditions of a specialized high-tech coal transshipment terminal with is located in the south part of Primorsky Krai. The economic efficiency affecting factors and their variations ranges were analysed. The research results can be used at the preliminary stages of ship design for general characteristics calculation and transportation costs optimization.

Surrogate Model-based Multi-Objective Optimization in Early Stages of Ship Design

The abstract is the early stages of ship design, the decision of the ship's main dimensions significantly impacts the ship's performance and the total cost of ownership. This paper focuses on an optimization approach based on surrogate models at the early stages of ship design. The objectives are to minimize power requirements and building costs while still satisfying the constraints. We compare three approaches of surrogate models: Kriging, BPNN-PSO (Backpropagation Neural Network-Particle Swarm Optimizer), and MLP (Multi-Layer Perceptron) in two multi-objective optimization algorithms: MOEA/D (Multi-Objective Evolutionary Algorithm Decomposition) and NSGA-II (Non-Dominated Sorting Genetic Algorithm II). The experimental results show that MLP surrogate models get the best performance with MAE 6.03, and BPNN-PSO gets the second position with MAE 7.2. BPNN-PSO and MLP with MOEA/D and NSGA-II improve the design with around 58% smaller adequate power and 6% less steel weight than the original design. However, BPNN-PSO and MLP have lower hypervolume than Kriging for both optimization algorithms MOEA/D and NSGA-II. On the other hand, Kriging has the most inadequate model accuracy performance, with an MAE of 22.2, but produces the highest hypervolume, lowest computational time, and far lower objective values than BPNN-PSO and MLP for both optimization algorithms, MOEA/D and NSGA-II. Nevertheless, the three surrogate model approaches can significantly improve ship design solutions and reduce work time in the early stages of design.

CFD assessment of the wind forces and moments of superstructures through RANS

In addition to wind tunnel tests and regression formulae, numerical simulation has begun to be used at the design stage of ships as a method for estimating the wind force and moments of superstructures. However, no specific approach has been proposed to verify the grid dependence around superstructures, and the degree to which differences in computational conditions affect the results has not yet been systematically clarified. Therefore, a new approach to grid sensitivity analysis is carried out. The effect of some computational conditions on the computed result is investigated using an in-house solver with an overset grid technique with a Japan Bulk Carrier(JBC) model. The method that verifies the grid sensitivity of the hull and the superstructures separately can obtain equivalent results to the method of simultaneously verifying both of them. The grid sensitivity analysis of the superstructures can be performed separately from the hull. The comprehensive comparative study reveals five findings: the blockage effect of the tank size is slight, the steady-state computation is capable of estimating as well as unsteady computation, wall function can be applied to object surfaces, a difference of wind profiles of incident flow can be recovered by the normalization based on the momentum integration in a shear flow, and the Reynolds number effect does not need to be considered if it is greater then 1.0×106. The computations for other ship types are also performed. The computed results show good agreement with the measured data, while the regression formula shows differences from the measured data in some cases. The above study has shown that steady-state CFD analysis is capable and viable in estimating the wind forces and moments of superstructures of a ship model in a wind tunnel for various ship types.

Comparative Study on Predicting Ship Maneuvering in Waves Using a Quasi-Steady Method and a Time Domain Approach

_ Numerical prediction of ship maneuvering in waves was considered in this article. The wave drift loads, computed using the potential flow theory, were added into the mathematical modeling group (MMG) equations to account for the effect of waves on the ship maneuvering. Two numerical methods were tested for dealing with the coupled maneuvering-seakeeping problem, namely a time domain approach and a quasi-steady method. For the former approach, a time domain seakeeping computation was conducted that parallels to the maneuvering simulation. For the later one, it is assumed that at each time of the maneuvering process, the wave-ship interaction is in a time harmonic status and, therefore, the wave drift loads could be evaluated using a frequency domain computation. Turning maneuvers of the S-175 container ship in regular waves were numerically tested. The results of the quasi-steady method and the time domain approach show good agreements, which proved the validity of the quasi-steady assumption. The wave drift loads during the turning process were also presented, demonstrating the significant effect of the added resistance on the maneuvering prediction, in contrast to the less remarkable effects of the lateral wave drift force and the wave drift yaw moment. Introduction Ship maneuverability is typically predicted under calm water condition. This provides valuable information at the ship design stage. However, an actual seagoing ship usually maneuvers in waves. To reliably assess a ship’s navigation safety and total performance in a seaway, it is deemed important to understand the maneuvering behavior of a ship in waves. Indeed, ship maneuverability in waves has been increasingly investigated in recent years. Although the physical experiment is still regarded as the most reliable way to investigate ship maneuverability in waves, there are more and more studies providing practical mathematical models of ship maneuvering prediction. Generally, a mathematical model that is suitable for investigating the maneuvering of a ship in waves has to encapsulate the traditional theories of calm water maneuvering and forward-speed seakeeping.

A K-Means Clustering Algorithm to Determine Representative Operational Profiles of a Ship Using AIS Data

Defining the appropriate functional requirements in the early ship design stage is important in order that costs that are caused by the over- or under-specified functional capabilities do not increase. This paper presents a K-means clustering algorithm for the determination of functional requirements. It uses automatic identification system (AIS) data from a reference ship to determine the representative operational profiles, which can support decision-makers in defining the functional requirements of ships that will be performing similar missions as those of the reference ship. In a case study, we used this method as part of a ship design project, in which the functional requirements of a battery-only electric ship are defined using AIS data from a reference ship. Results indicate that the cost can be reduced by determining the functional requirements using the proposed method.

Prediction of seakeeping in the early stage of conventional monohull vessels design using artificial neural network

Nowadays seakeeping is mostly analyzed by means of model testing or numerical models. Both require a significant amount of time and the exact hull geometry, and therefore seakeeping is not taken into account at the early stages of ship design. Hence the main objective of this work is the development of a seakeeping prediction tool to be used in the early stages of ship design.This tool must be fast, accurate, and not require the exact hull shape. To this end, an artificial intelligence (AI) algorithm has been developed. This algorithm is based on Artificial Neural Networks (ANNs) and only requires a number of ship coefficients of form.The methodology developed to obtain the predictive algorithm is presented as well as the database of ships used for training the ANN. The data were generated using a frequency domain seakeeping code based on the boundary element method (BEM). Also, the AI predictions are compared to the BEM results using both, ship hulls included and not included in the database.As a result of this work it has been obtained an AI tool for seakeeping prediction of conventional monohull vessels

A study of the Development of Ship Integrated Combat Capability Operational Test and Evaluation using Missile Live-Fire and Reaction Time Analysis

This study aims to introduce missile live-fire during the ship operational test and evaluation(T&E) as a means of verifying the integrated combat capability(ICC) of various systems installed on naval ships. The research method identified domestic and foreign T&E systems and cases, and reports related to ICC, which were written during the ship's design stage. As a result of research, Republic of Korea is not conducting the missile live-fire at the ship T&E stage due to the lack of relevant systems, while the U.S. is conducting it based on the mission-based T&E and the end-to-end test system. As a way to improve within the current domestic ship acquisition systems, the reaction time analysis, a quantitative analysis result of ICC calculated at the ship basic design stage, was proposed to be verified by missile live-fire during ship operational T&E.