Study Reduction of Resistance on The Flat Hull Ship of The Semi-Trimaran Model: Hull Vane Vs Stern Foil

Flat hull ships is appraised for its superiority due to the manufacturing simplicity and lower investment costs, yet the ship has its own weakness for it requires a greater resistance. As a matter of fact, a significant reduction on the resistance can be done with foil installation but it is necessary to study the optimal position of the foil installation. This study is aimed at revealing the effectiveness of the Hull Vane and Stern Foil installation in reducing the resistance experienced by the flat hull ship of the semi-trimaran model. The research was conducted by comparing the resistance experienced by the flat hull ship of the semi-trimaran model without foil, Hull vane and Stern foil installations. In addition, the disclosure of resistance experienced by each ship model was carried out by using CFD simulation. The simulation results revealed that the installation of the Hull vane and Stern foil was able to reduce the resistance experienced by the flat hull ship of the semi-trimaran model. The largest reduction occurred in Froude number 1.1, where the Hull vane installation was able to reduce resistance by 12.44% and on the ship model with Stern foil installation the resistance reduction was 5.25%. Based on the results of this CFD simulation, it can be concluded that the Hull Vane installation is more optimal in reducing resistance on the flat hull ship of the semi-trimaran model.

A NUMERICAL SIMULATION INVESTIGATION OF THE HYDRODYNAMIC MOTIONS OF A SHIP ADVANCING IN WAVES

This study establishes a relationship diagram of the ship-wave interaction under a ship advancing in waves. A finite difference method based on volume of fluid (VOF) principles was used to simulate the hydrodynamic motions of a ship advancing in waves. A ship model was constructed using a computer aided design (CAD) tool. The computational fluid dynamic (CFD) technique was used to calculate the hydrodynamic motions effect of a ship sailing in waves at varying angles of incidence. This study investigates a number of significant related parameters, such as the speed of the ship model, the various wave incidence angles, the wave height, and the navigation time. A chart is also used to show the flow field, and changes in the six degrees of freedom motion and continually compare changes in the drag force.

VECTOR FIELD GUIDANCE LAW FOR CURVED PATH FOLLOWING OF AN UNDERACTUATED AUTONOMOUS SHIP MODEL

A vector field guidance law and control system for curved path following of an underactuated surface ship model is presented in this paper. In order to obtain the curved path, continuous derivatives piecewise cubic Hermite interpolation is applied for path generation based on the predefined waypoints. A heading autopilot controller is designed based on 2nd order Nomoto’s model and its stability is guaranteed by the Diagram of Vyshnegradsky method. The parameters of Nomoto model are estimated using least square support vector machine based on the manoeuvring tests. The vector field guidance law is applied for both straight and curved path-following control of an underactuated surface ship model. In order to demonstrate the performance, the classical guidance law based on line-of-sight, is adopted for comparison. The results show that the vector field method is capable to solve the guidance problem of underactuated surface ships.

ESTIMATION OF HYDRODYNAMIC COEFFICIENTS OF A NONLINEAR MANOEUVRING MATHEMATICAL MODEL WITH FREE-RUNNING SHIP MODEL TESTS

Free-running model tests have been carried out based on a scaled chemical tanker ship model, having a guidance, control and navigation system developed and implemented in LabVIEW. In order to make the modelling more flexible and physically more realistic, a modified version of Abkowitz model was introduced. During the identification process, the model’s structure is fixed and its parameters have been obtained using system identification. A global optimization algorithm has been used to search the optimum values and minimize the loss functions. In order to reduce the effect of noise in the variables, different loss functions considering the empirical errors and generalization performance have been defined and implemented in the system identification program. The hydrodynamic coefficients have been identified based on the manoeuvring test data of free-running ship model. Validations of the system identification algorithm were also carried out and the comparisons with experiments demonstrated the effectiveness of the proposed system identification method.

Propulsion simulation on fully appended ship model

This study presents the numerical investigation for the flow around the propeller of the ONR Tumblehome combatant in open water and for the flow around the same ship in the case of self-propulsion with actuator disk method. Computational Fluid Dynamics based on RANS-VOF solver have been used in order to analyse the flow. The free surface treatment is multi-phase flow approach, incompressible and nonmiscible flow phases are modelled through the use of conservation equations for each volume fraction of phase. Accuracy involves close attention to the physical modelling, particularly the effects of turbulence, as well as the numerical discretization.

Risk Assessment Fishing Vessel Based for the Intact Ship Stability

Application of safety assessment and risk analysis using a risk-based approach for ship stability in ship operations at sea. However, there are currently no specific criteria and computational methods for risk assessment of ship stability. Based on the stability requirements for fishing activities at sea, the ship stability criteria will be explained in detail in this study. Calculation of stability used to obtain the GZ enforcement arm is carried out with the help of software for the shaking period using the International Maritime Organization (IMO) formula. Next, how to calculate parameters and determine certain coefficients for risk assessment of ship stability, and how to redraw the stability curve. Finally, proposed method is applied to ship model with comments and recommendations for monitoring to provide and overview. The study result indicate that the five loading conditions that occur on the ship have good stability by the criteria set by the International Maritime Organization (IMO). The value of GMt in each condition includes condition 1 and so on, 0.48; 0.48; 0.47; 0.46; 0.43. The results are presented in the form of F-N. Finally the sensitivity of the model is evaluated along with the assessment of associated uncertainties. The FN graph represents acceptable areas and unacceptable areas. Based on the results of data processing, the highest GM at GM Load-case 5 0.638 meters is in the Acceptable area. While Load-case 1 to Load-case 4 GM values sequentially Load-case 1: 0.487 meters; Load-case 2: 0.488 meters; Load-case 3: 0.47 meters; Load-case 4: 0.468 meters; is in an unacceptable area Unacceptable.