Preliminary Bulbous Bow Design Tool Applying K Nearest Neighbours Classification and Regression Model

Designing bulbous bows for ships remains a challenging task.  Their impact on different design attributes as well as their change in performance when operating off their intended design condition renders this as a multidimensional problem.  This paper explores the application of machine learning techniques to a sample of in-service vessel data to develop a preliminary design tool.  The ships' data was analysed together with their bulbous bow data to generate machine learning models using a supervised approach.  The K Nearest Neighbours Classifier and Regression models were used as the basis of the tool.  Together, these models can be used to predict whether to install a bulbous bow and the recommended dimensionless coefficients for new vessels. Generating this preliminary bulbous bow design tool required the introduction of new dimensionless coefficients that discretise the bulbous bow's longitudinal section.  The preliminary design tool gives the designer the ability to determine whether a bulbous bow should be fitted and, if so, to obtain an initial estimate of the bulbous bow required for the vessel being designed, based on key input parameters that relate to the ship and its operation.  The new design tool is demonstrated to provide preliminary design details for bulbous bows through the case studies

Prediction of the Risk of Capsize of Small Ships

The lack of a necessary rational framework for assessing ship stability was the main concern of this research. The aim was to develop a rational philosophy and a logical procedure of assessing intact stability in order to ensure a consistent and unified approach to design for operation and for survival. The method uniquely brings together a linearised analysis for assessing a potentially dangerous roll motion with a probabilistic assessment of ship performance in rough seas on a standard test-track. This represents a significant advance on previous research. A novel feature of the analysis was that prediction of the extreme capsize roll motion was not attempted per se. Instead a reduced level of roll response termed "potentially dangerous" roll motion was selected (based on discussions with seagoing personnel) beyond which there was evidence that loss of the vessel is likely. Validation of the linear spectral analysis used in the simulations was performed using full scale trial results of a fisheries protection vessel. Provided that measured values of roll damping coefficient were used, the predicted values of extreme roll closely matched the maximum values experienced on sea trials up to the chosen value of critical roll angle of 30 degrees. Particular attention was paid to the realistic modelling of total system behaviour in rough seas. Families of wave spectra were used to represent the complete range of wave conditions encountered in nature. Avoidance and pacifying seamanship were incorporated based on the results of available trials data and discussions with serving masters. Independent (Bernoulli) trials procedures were used to calculate the cumulative probability of a critical roll motion being exceeded at least once during the vessel's passage through the test-track. The value of critical motion exceedance obtained was 5x10ˉ² for the fisheries protection vessel which has a large metacentic height and is reported to have good seakeeping characteristics.British Maritime Technology Umited, Feltha

Time Domain Simulation of SWATH Ship Motions

This thesis presents a technique for predicting the coupled heave and pitch motions of SWATH vessels in the time domain. The emphasis is on completing the essential foundation work required for developing a fully comprehensive, non-linear time domain model. A procedure for solving the coupled motion equations is developed for linear motions and then validated using predictions obtained from equivalent frequency domain analysis. Hydrodynamic quantities are calculated using a two dimensional strip theory method which involves solving source distribution boundary value conditions using the Frank Close-Fit technique. The methods employed for introducing some nonlinear effects caused by the time dependency of motion coefficients and wave exciting forces and moments are described. Results from a computer program written to perform the time domain calculations are used to illustrate the non-linear phenomena and to demonstrate the improved correlation with model test data that can be achieved using non-linear time domain analysis. Further development work is proposed. The influence of motion control fins and the occurrence of cross-structure slamming require careful consideration in SWATH ship design. Suitable approaches to introducing these non-linear effects into the simulation are suggested

Numerical Investigation of Extended Stern to Reduce Resistance of Planing Hull

The attributes of a high-speed vessel depend on various factors, such as trim angle, speed, center of gravity, and deadrise angle. The ship\u27s trim angle will affect the ship\u27s drag performance. Attempts to control trim have been made by adding stern appendages and modifying the hull. This study aims to analyze the performance of deep-V planing-hull ship drag by modifying the ship\u27s stern. The stern modification investigation was carried out by adding length to the stern based on angles of 100, 200, and 300. This investigation evaluates resistance, trim, and heave while ignoring changes in ship displacement. The prediction of resistance and ship movements was simulated using the Reynold Averaged Navier-Stokes (RANS) equations to solve the problem. Numerical simulation applied the Computational Fluid Dynamics (CFD) based on finite volume method with an overset of techniques. Validation studies ensured numerical simulations have good accuracy based on comparisons with experimental model tests conducted by previous researchers. The pressure distribution caused by the extended stern affected the ship\u27s drag, further demonstrating a better trim control. The results of the stern modification simulation revealed that the resistance was reduced at Fr 0.58–0.87. Extended sterns with an angle of 30° indicated the best results, with a resistance reduction percentage of 26% at Fr 0.58. However, drag increased at Fr speeds > 1.45 as the ship\u27s speed increased

The Drift Angle Theory Applied To Ship Manoeuvring Models

A marine vehicle manoeuvring model is concerned with the ability to simulate the status of a vehicle to various demanded controls on a digital computer. Such models have both shore based and sea going applications that are beneficial to the mariner, enhance safety of life at sea and aid in protecting the marine environment The mathematical representation of marine vehicles has generally been conducted by the measurement of the forces and moments that are experienced by a vehicle, in terms of a series of numbers collectively known as hydrodynamic coefficients. This has resulted in the non-linear force modular model which is considered to be the most accurate and versatile mathematical modelling technique. This thesis presents the results from research conducted into the construction of an accurate mathematical model of a patrol craft Picket Boat Nine. The non-linear force modular modelling technique was initially adopted. The required hydrodynamic coefficients were evaluated by the use of full scale sea trials, scale model testing techniques and by semi-empirical methodologies; by the installation of a towing tank, a data monitoring and acquisition system onboard Picket Boat Nine. An alternative new method for mathematically describing marine vehicles has also been developed based upon the drift angle theory. The existence and magnitude of the drift angle has been transformed into a set of hydrodynamic curves that mathematically represent a marine vehicle's manoeuvrability and into a method of determining the track history of a marine vehicle when underway. These two components have been developed into a new form of mathematical model This new approach to mathematical modelling has been tested by full scale sea trials in Picket Boat Nine and with comparison to a force modular model that demonstrates the stature and potential of this method. The results indicate that further research is required to include external disturbances and to prove its validity to other marine vehicles.Britannia Royal Naval Colleg

Roll motion on small traditional Norwegian fishing vessels

Roll motion is one of the six degrees of freedom and is the most difficult to predict, as roll motion is extremely sensitive to the viscous effect and induced flow separation. The smaller fishing vessel fleet commonly operates in almost all weather conditions, and sometimes in remote areas with cold arctic water where rescue can be far away and difficult. The safety of fishers depends on the vessel's characteristic to resist and maintain stability in high seas that can lead to large-amplitude motion with a combination of wave-induced ship motions. Roll motion can be a problem for vessels without any appendages that reduce the roll motion, e.g. bilge keels - stabilizers with no moving parts, form the most straightforward and cheapest element that can help decrease this motion. Through the last four decades, studies and investigation of roll motion use the approach developed by Ikeda et al. in the '70s and is the foundation to the guidelines presented by International Towing Tank Committee (ITTC). This thesis uses the procedures and guidelines from ITTC and compares the effects of bilge keel between model experiments and the numerical result

Investigation of the optimum longitudinal single transverse step location for a high-speed craft

One of the crucial aspects of the conceptual design of a stepped planing hull is the prediction of its performance. To improve performance, the prediction of total resistance must become more accurate. In the field of research, both towing tank experiments and numerical analysis may be used to achieve this goal. In this study, experiments were conducted initially to investigate total resistance of a relatively high-speed craft without a transverse step. Later, numerical computations were carried out to validate the experimental results. After it was determined that the test results and CFD methods were in good agreement, the experimental method continued to investigate the resistance properties of the hull with four different configurations to evaluate the optimal longitudinal position of a single transverse step. The ideal longitudinal position of the single transverse step was evaluated based on a similar relatively high-speed hull with a velocity of up to beam Froude number (FrB) 2.56 in this study, focusing on the FrB range between 2.30 and 2.45

Lifespan Estimation of Galvanized Steel and Stainless Steel Pipe

This research presents a comparative study focused on estimating the lifespan of galvanized steel pipes and stainless steel pipes within the context of a ballast system. Ballast systems play a crucial role in maintaining the stability and trim of vessels, making the longevity of the associated piping materials essential for maritime operations. This research aims to provide insights into the corrosion behavior and overall durability of galvanized steel and stainless steel pipes employed in ballast systems. The investigation involves an in-depth analysis of corrosion mechanisms specific to both galvanized steel and stainless steel pipes in the corrosive marine environment. The influence of factors such as salinity, and immersion time is examined. By understanding the distinct corrosion behavior of galvanized steel and stainless steel pipes, maritime industry stakeholders can make informed decisions regarding material selection, maintenance schedules, and potential retrofitting options. Ultimately, the insights gained from this study contribute to the sustainability and operational efficiency of maritime transport by enabling the optimization of ballast system infrastructure. As regulations and environmental considerations evolve, a comprehensive understanding of the lifespan estimation of galvanized steel and stainless steel pipes aids in mitigating potential failures, reducing downtime, and ensuring the safety and reliability of vessel operations. It is shown that the lifespan of stainless steel is longer than that of galvanized pipe

Optimal weather routeing procedures for vessels on trans-oceanic voyages

Merged with duplicate record 10026.1/2726 on 06.20.2017 by CS (TIS)Three sets of algorithms are formulated for use in a variety of models :- * Ship performance algorithms. * Optimisation algorithms. * Environmental data. Optimisation models are constructed for deterministic minima, with time, fuel and cost objective functions. Models are constructed for an actual ship, (M. V. DART ATLANTIC), and realistic working solutions are obtained based on real-time weather information, simulating an actual on-board, computer based system, using dynamic programming. Several combinations of algorithm types are used in the the models, enabling comparisons of effectiveness. Thus, the ship performance algorithms incorporate severally; simple ship speed loss curves, ship resistance, ship motions and ship motion criteria databases devised from a linear seakeeping model. Limitations of the models are discussed from the routeing examples given. State space restrictions and originally devised methods to aid convergence in the models are discussed. Extension of the forecasted environmental data is achieved by a variety of methods and comparisons sought. In particular ECMWF surface pressure files are interrogated to produce sea wave fields over the extended period, establishing main disturbance centres. The variety of algorithms formulated in this work has facilitated real-time comparisons, this is particularly effective in route-updating. The development of these models and the methods used to extend the forecast period, and the comparisons and associated results stemming from these models are viewed as an original contribution to real-time weather routeing of ships.Oceanroutes (UK) Ltd and Oceanroutes Inc, US

Comparación computacional de motores AC y DC ante cambios hidrodinámicos en embarcaciones marítimas pesqueras

The objective of this article is to make a comparison in a computational environment between an alternating current motor and a direct current motor is made for dynamic variations in the propulsion of an artisanal fishing boat. Initially, the boat was simulated in the Maxsurf software to obtain the dynamic behaviors for pitching, rolling, yawing, and heave motions with wind and wave perturbations for a Pierson Moskowitz spectrum. Subsequently, the motors are selected and in Matlab/Simulink software and a torque behavior required by the vessel to act on the resistance presented in each dynamic motion is proposed. This allows for analyzing the required mechanical and electrical conditions, using the curves obtained in the simulation. Finally, it is concluded that taking into account the criteria of torque, power, speed, and current, the results obtained show that the DC motor is more efficient than the three-phase AC motor for artisanal fishing vessel applications. In addition, the two motors require greater effort to overcome the disturbance related to the rolling motion in the steady-state, while in the transient state the DC motor requires a higher starting torque and the AC motor presents oscillations, which are undesirable disturbances because they produce instability in the electrical system. Additionally, it is important to take into account the energy source that feeds the motors, which can be alternating current or direct current.El objetivo de este artículo fue realizar la comparación en un ambiente computacional entre un motor de corriente alterna y un motor de corriente continua ante variaciones dinámicas en la propulsión de una embarcación marítima de pesca artesanal. Inicialmente, se simuló la embarcación en el software Maxsurf con el objetivo de obtener los comportamientos dinámicos para los movimientos de cabeceo, balanceo, guiñada y oleaje con perturbaciones de viento y ola para un espectro de Pierson-Moskowitz. Posteriormente, se seleccionaron los motores en el software Matlab/Simulink, donde se propone un comportamiento de torque requerido por la embarcación para actuar ante la resistencia presentada en cada movimiento dinámico. Esto permitió analizar las condiciones mecánicas y eléctricas requeridas mediante las curvas obtenidas en la simulación. Finalmente, teniendo en cuenta los criterios de torque, potencia, velocidad, y corriente, los resultados obtenidos mostraron que el motor DC presenta mayor eficiencia que el motor AC trifásico para aplicaciones de buques de pesca artesanal. Además, se evidenció que los dos motores requieren mayor esfuerzo para vencer la perturbación relacionada al movimiento de balanceo en estado estable, mientras que, en el estado transitorio, el motor DC requiere un par de arranque mayor y el motor AC presenta oscilaciones, las cuales son perturbaciones indeseables debido a que producen inestabilidad en el sistema eléctrico. Es importante tener en cuenta la fuente energética que alimenta los motores que pueden ser de corriente alterna o corriente continua