Ship Trim Optimization: Assessment of Influence of Trim on Resistance of MOERI Container Ship

Environmental issues and rising fuel prices necessitate better energy efficiency in all sectors. Shipping industry is a stakeholder in environmental issues. Shipping industry is responsible for approximately 3% of global CO2 emissions, 14-15% of global NOX emissions, and 16% of global SOX emissions. Ship trim optimization has gained enormous momentum in recent years being an effective operational measure for better energy efficiency to reduce emissions. Ship trim optimization analysis has traditionally been done through tow-tank testing for a specific hullform. Computational techniques are increasingly popular in ship hydrodynamics applications. The purpose of this study is to present MOERI container ship (KCS) hull trim optimization by employing computational methods. KCS hull total resistances and trim and sinkage computed values, in even keel condition, are compared with experimental values and found in reasonable agreement. The agreement validates that mesh, boundary conditions, and solution techniques are correct. The same mesh, boundary conditions, and solution techniques are used to obtain resistance values in different trim conditions at Fn = 0.2274. Based on attained results, optimum trim is suggested. This research serves as foundation for employing computational techniques for ship trim optimization

NUMERICAL MODELLING AND STUDY OF PARAMETRIC ROLLING FOR C11 CONTAINERSHIP IN REGULAR HEAD SEAS USING CONSISTENT STRIP THEORY

In this paper, a numerical model was proposed to simulate the parametric rolling of ships in head seas. The method was developed in time-domain based on strip theory, in which a consistent way of estimating the radiation forces was applied using impulse response function method. To take the coupling effect into account, the heave and pitch motions were solved together with the rolling motion. Also, the Froude-Krylov forces and hydrostatic forces were evaluated on the instantaneously wetted surface of the ship, in order to model the time varied restoring rolling moment in waves. Based on the developed numerical model, the parametrically roll motions of C11 containership was simulated. The influence of roll damping was investigated using two different methods, and the numerical results were compared with model tests. The comparative study shows that results obtained by the proposed method generally agree well with experimental data. Discussions and possible improvements of the current numerical model were also presented in this paper, with regard to the numerical deviation between the numerical and experimental results when the wave steepness was larger than 0.04

Added Resistance Simulation of Blunt Ship in Short Wave

Highlights: Added resistances of KVLCC2 in short waves are predicted by 2 nd order TEBEM and compared with published results by other numerical solutions and experimental results. It is found the strength of low-pass filter in numerical treating the free surface elevation plays an important role for accurate predicting the added resistance in short wave

Linear time-domain strip method for ship motion prediction

[Objectives] In order to study the nonlinear strip method for prediction of ship motions in waves, this paper develops a linear time-domain strip method to make a preliminary exploration.[Methods] Under the assumptions of strip theory,the boundary conditions for 2D section are established, and after the calculation of hydrodynamic force coefficient of 2D section,the force and motion response of the whole ship are solved. The numerical differentiation algorithm is used to solve the partial derivative of velocity potential along the ship length direction. The calculated hydrodynamic force coefficient of Wigley I ship and the calculated motion response of KVLCC2 and a 8 000 TEU container ship are compared with the calculated and test values of other related methods.[Results] It is found that the results are generally consistent with the model test results,and can be applied in practice.[Conclusions] This study,to some extent,lays a basis for the future research on the nonlinear time-domain strip method for ship motion prediction

A high‐order harmonic polynomial method for solving the Laplace equation with complex boundaries and its application to free‐surface flows. Part I: Two‐dimensional cases

A high‐order harmonic polynomial method (HPM) is developed for solving the Laplace equation with complex boundaries. The “irregular cell” is proposed for the accurate discretization of the Laplace equation, where it is difficult to construct a high‐quality stencil. An advanced discretization scheme is also developed for the accurate evaluation of the normal derivative of potential functions on complex boundaries. Thanks to the irregular cell and the discretization scheme for the normal derivative of the potential functions, the present method can avoid the drawback of distorted stencils, that is, the possible numerical inaccuracy/instability. Furthermore, it can involve stationary or moving bodies on the Cartesian grid in an accurate and simple way. With the proper free‐surface tracking methods, the HPM has been successfully applied to the accurate and stable modeling of highly nonlinear free‐surface potential flows with and without moving bodies, that is, sloshing, water entry, and plunging breaker