International Shipbuilding Progress - Volume 54, issue 4

Article Type: Other

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 189-189, 2007

Authors: Sheinberg, Rubin | Stambaugh, Karl | Eisele, Andrew | Leadbetter, Ross

Article Type: Research Article

Abstract: Ships that are routinely called upon to perform demanding missions that often require operation in extreme weather environments will benefit from the development of heavy weather guidance (HWG). This guidance is intended to assist vessel operators in the selection of safe speed and heading in severe weather conditions, thereby reducing the probability of dynamic instabilities and potentially disastrous capsize events. A simplified method of estimating the encounter-dependent capsize probability based on the results of time domain simulations is outlined along with procedures to extend these estimates to fully characterize the time-dependency of the probability. Additionally, an alternative method of calculating …capsize probability involving integration of the joint probability density function (JPDF) of wave height and length over a region of predicted critical waves. Show more

Keywords: Dynamic stability, operator guidance, heavy weather, risk assessment, mission planning, capsize, probability

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 191-205, 2007

Authors: Neves, Marcelo A.S. | Rodríguez, Claudio A.

Article Type: Research Article

Abstract: Parametric resonance in regular waves is discussed. A set of non-linear equations is employed to describe the coupling between heave-roll-pitch modes. Limits of stability are the main area of interest of the paper. The present paper explores the influence of third order nonlinearities as well as the relevance of coupling between the vertical modes and the roll motion in the limits of stability. The influence of initial conditions on the development of roll amplifications is investigated and the effect of coupled or uncoupled modelling of the roll motion is addressed.

Keywords: Parametric resonance, limits of stability, ship stability, nonlinear coupling

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 207-225, 2007

Authors: Bulian, Gabriele | Francescutto, Alberto

Article Type: Research Article

Abstract: In this paper, the problem of dangerous conditions induced by variations of restoring in waves is addressed, with particular attention to parametric roll. An analytical model for the study of roll motion in irregular longitudinal long crested waves is presented. Stochastic stability boundaries in the first parametric resonance region are provided analytically. Nonlinear/non-Gaussian roll response above threshold is determined numerically and compared with experiments. A semi-empirical methodology is proposed to extend the classical deterministic static stability assessment to a rational probabilistic framework taking into account hydrostatic restoring variations in waves and different environmental conditions. Examples of application are provided.

Keywords: Irregular sea, parametric roll, nonlinear motions, stochastic stability, pure loss of stability, stability criteria, performance based criteria

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 227-248, 2007

Authors: Spanos, Dimitris | Papanikolaou, Apostolos

Article Type: Research Article

Abstract: A time-domain numerical simulation method is applied for the investigation of parametric roll resonance in regular head waves for two different types of vessels, namely a fishing vessel and a RoRo ship. The employed mathematical model captures satisfactorily most of the parameters relevant to the problem hence enables an improved reproduction and understanding of the complicated non-linear parametric roll phenomenon. The coupling between the induced roll and pitch motions along with the nonlinear character of the restoring moment associated with large amplitude wave induced motions have been found to be the determinant factors of the observed roll resonance phenomenon. Furthermore, …a strong dependence of the roll resonance on both the wave frequency of encounter and the incident wave height has been recorded. The obtained numerical results were compared with corresponding available experimental measurements and commented. Show more

Keywords: Time-domain, numerical simulation, parametric resonance, roll motion, non-linear dynamics, dynamic stability, capsize

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 249-267, 2007

Authors: Umeda, Naoya | Hori, Masatoshi | Hashimoto, Hirotada

Article Type: Research Article

Abstract: For developing design and operational criteria to be used at the International Maritime Organization (IMO), critical conditions for broaching are explored in the light of bifurcation analysis. Since surf-riding, which is a prerequisite to broaching, can be regarded as a heteroclinic bifurcation, one of global bifurcations, of a surge–sway–yaw–roll model in quartering waves, the relevant bifurcation condition was mathematically formulated and then a numerical procedure for obtaining its solution was presented with successful example. This identified bifurcation condition was compared with direct numerical simulation in time domain. As a result, it was confirmed that the heteroclinic bifurcation provides a boundary …between motions periodically overtaken by waves and non-periodic motions such as surf-riding, broaching and so on. Then a local bifurcation analysis was applied to the surf-riding equilibria. This results could explain a boundary between stable surf-riding and oscillatory surf-riding as a Hopf bifurcation. Furthermore, comparison with free-running model experiments shows some discrepancies and an improvement with an aid of nonlinearity in wave-induced surge force is presented. Show more

Keywords: Broaching, surf-riding, capsizing, heteroclinic bifurcation, Hopf bifurcation, intact stability

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 269-281, 2007

Article Type: Other

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 283-283, 2007

Authors: Spyrou, Kostas J. | Roupas, Iraklis

Article Type: Research Article

Abstract: We are proposing to upgrade Wendel's probabilistic concept of assessment of ship subdivision that has been applied in IMO's probabilistic regulatory framework, including the recent harmonized one. Unlike Wendel's concept where the focus is on the ship, here the emphasis is placed on passenger survival. Index A is replaced by a new index reflecting passenger risk. Damage scenarios that lead to ship loss may still contribute to safety, according to the relation between time-to-sink and evacuation time. A calculation procedure is proposed that exploits recent research. Demonstration of the methodology through preliminary application to a modern ferry is included.

Keywords: Ship, damage stability, probabilistic, risk assessment

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 285-303, 2007

Authors: Ruponen, Pekka | Sundell, Tom | Larmela, Markku

Article Type: Research Article

Abstract: A new simulation method for progressive flooding has been developed. The method is based on the pressure-correction technique and it is capable of dealing with coupled water and airflows. The iterative structure ensures time-accurate simulations with complex systems of flooded compartments. The principles of the simulation method are briefly described with the main emphasis on the simulation of the performed model tests and on the validation of the method. Furthermore, the simulation method is tested with a case study in order to research the effects of the level of the modeling details and ventilation.

Keywords: Progressive flooding, simulation method, model test, validation, case study

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 305-321, 2007

Authors: Vanem, Erik | Rusås, Sigmund | Skjong, Rolf | Olufsen, Odd

Article Type: Research Article

Abstract: This paper presents a risk-based approach for viewing damage stability of passenger ships in a holistic way. It is recommended that such an approach is adopted in the design of new ships in order to control the risk associated with collision scenarios. In addition, the methodology presented can be applied on segments of the existing fleet of passenger ships in order to gain a better understanding of the risk. Within a risk-based framework, the methodology can be utilized in order to establish reasonable performance criteria for damage stability in a consistent and rational way.

Keywords: Damage stability, passenger ship safety, risk analysis, collision, maritime safety, design for safety, risk-based design

Citation: International Shipbuilding Progress, vol. 54, no. 4, pp. 323-337, 2007