Using time domain nonlinear ship motion simulations to assess safety of people and cargo onboard a container vessel

2015 ◽  
pp. 119-130
Keyword(s):  
Time Domain ◽  
Ship Motion ◽  
Nonlinear Ship Motion

The Effects of Inner-Liquid Motion on LNG Vessel Responses

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
S. J. Lee ◽  
M. H. Kim
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Surface Profile ◽  
Ship Motion ◽  
Liquid Sloshing ◽  
Diffraction Radiation ◽  
Time Domain Simulation ◽  
Coupling Effects ◽  
The Time Domain ◽  
Vessel Motion

The coupling and interactions between ship motion and inner-tank sloshing are investigated by a potential-viscous hybrid method in the time domain. For the time-domain simulation of vessel motion, the hydrodynamic coefficients and wave forces are obtained by a potential-theory-based 3D diffraction/radiation panel program in the frequency domain. Then, the corresponding simulations of motions in the time domain are carried out using the convolution-integral method. The liquid sloshing in a tank is simulated in the time domain by a Navier–Stokes solver. A finite difference method with SURF scheme assuming the single-valued free-surface profile is applied for the direct simulation of liquid sloshing. The computed sloshing forces and moments are then applied as external excitations to the ship motion. The calculated ship motion is in turn inputted as the excitation for liquid sloshing, which is repeated for the ensuing time steps. For comparison, we independently developed a 3D panel program for linear inner-fluid motions, and it is coupled with the vessel-motion program in the frequency domain. The developed computer programs are applied to a barge-type floating production storage and offloading (FPSO) hull equipped with two partially filled tanks. The time-domain simulation results show reasonably good agreement when compared with Maritime Research Institute Netherlands (MARIN’s) experimental results. The frequency-domain results qualitatively reproduce the trend of coupling effects, but the peaks are in general overpredicted. It is seen that the coupling effects on roll motions appreciably change with filling level. The most pronounced coupling effects on roll motions are the shift or split of peak frequencies. The pitch motions are much less influenced by the inner-fluid motion compared with roll motions.

Experimental Study on a Relation Between Nonlinear Hydrodynamic Forces and Wave-Induced Ship Motions

2019 ◽  
Author(s):  
Masakazu Taguchi ◽  
Masashi Kashiwagi
Keyword(s):  
Large Amplitude ◽  
Equations Of Motion ◽  
Linear Equations ◽  
Hydrodynamic Forces ◽  
Ship Motion ◽  
Ship Motions ◽  
Practical Calculation ◽  
Wave Loads ◽  
Nonlinear Ship Motion ◽  
Wave Induced

Abstract Nowadays, in maritime industries, container ships increase in size and they have large flares, which may induce nonlinear wave loads in large-amplitude waves. It is also well known that hydrodynamic forces acting on a ship and resulting ship motions show nonlinearities at some range of wave frequencies. Therefore, we should investigate not only correct estimation of wave loads and ship motions, but also nonlinear ship-motion characteristics in large-amplitude waves. However, it is not that clear which nonlinear hydrodynamic force terms are dominating for the nonlinearity in the ship motions. Although the linear equations of motion have been used, they should be modified to incorporate at least the most important nonlinear hydrodynamic forces and to establish a practical calculation method taking account of only the indispensable nonlinear terms. In this research, we did extensive experimental measurement of hydrodynamic forces and wave-induced ship motions, with which we aim to understand what are practically important nonlinear terms, and to derive practical nonlinear ship motion equations through numerical computation and comparison with experimental data.

Analysis of an Asymmetrical Bridle Towline Model to Stabilise Towing Performance of a Towed Ship

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
A. Fitriadhy ◽  
H. Yasukawa ◽  
T. Yoneda ◽  
K. K. Koh ◽  
A. Maimun
Keyword(s):  
Time Domain ◽  
Feasible Solution ◽  
Ship Motion ◽  
Solution Model ◽  
Time Domain Simulation ◽  
Point Position ◽  
Remarkable Reduction

This paper addresses an asymmetrical bridle towline model as a feasible solution model to stabilize towing performance of a towed ship. The basic thinking behind the approach adopted, is to deal with a better towing stability than employing the typical towline model1. Several towing parameters which may affect a towed ship motion behaviour i.e., tow angle and tow point position, are investigated theoretically. The nonlinear numerical time-domain simulation showed that the increase of towing angle up to 30 degrees and shifting tow point from 0.5 to 0.8 resulted in remarkable reduction in slewing motion of the unstable towed ship and the towline tension, which enhances effectively her towing stability.

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