Methods for estimating parametric rolling

2010 ◽  
pp. 43-54
Author(s):  
A Turk ◽  
J Prpi_-Or_i_ ◽  
S Silva ◽  
C Soares
Keyword(s):  
Parametric Rolling

scholarly journals Comparison of a Floating Cylinder with Solid and Water Ballast

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2487 ◽  
Author(s):  
Roman Gabl ◽  
Thomas Davey ◽  
Edd Nixon ◽  
Jeffrey Steynor ◽  
David M. Ingram
Keyword(s):  
Free Surface ◽  
Wave Direction ◽  
Floating Structure ◽  
Parametric Rolling ◽  
Rotation Direction ◽  
Wide Range ◽  
Heave Motion ◽  
Floating Platforms ◽  
Floating Objects ◽  
Validation Experiments

Modelling and understanding the motion of water filled floating objects is important for a wide range of applications including the behaviour of ships and floating platforms. Previous studies either investigated only small movements or applied a very specific (ship) geometry. The presented experiments are conducted using the simplified geometry of an open topped hollow cylinder ballasted to different displacements. Regular waves are used to excite the floating structure, which exhibits rotation angles of over 20 degrees and a heave motion double that of the wave amplitude. Four different drafts are investigated, each with two different ballast options: with (water) and without (solid) a free surface. The comparison shows a small difference in the body’s three translational motions as well as the rotation around the normal axis to the water surface. Significant differences are observed in the rotation about the wave direction comparable to parametric rolling as seen in ships. The three bigger drafts with free surface switch the dominant global rotation direction from pitch to roll, which can clearly be attributed to the sloshing of the internal water. The presented study provides a new dataset and comparison of varying ballast types on device motions, which may be used for future validation experiments.

Control of Unstable Ship Motions Using Anti-Rolling Tanks: Erosion of Safe Basins

2010 ◽  
Author(s):  
Marcelo A. S. Neves ◽  
Claudio A. Rodri´guez ◽  
Jorge A. Merino ◽  
Jerver E. M. Vivanco ◽  
Jose´ C. Villago´mez Rosales ◽  
...  
Keyword(s):  
Quantitative Assessment ◽  
Initial Conditions ◽  
Dynamical Behavior ◽  
Design Procedure ◽  
Ship Motions ◽  
Numerical Techniques ◽  
Liquid Motion ◽  
Critical Amplitude ◽  
Parametric Rolling ◽  
Limits Of Stability

The objective of the paper is to apply modern numerical techniques of nonlinear dynamics to the problem of control of the roll motion employing U-shaped anti rolling tanks (ART). Parametric rolling in head seas is the focus of the paper. A transom stern small vessel, well known for her tendency to develop strong parametric excitation is investigated. Nonlinear equations are employed to describe the liquid motion inside the tank, the forces and moments generated by the tank on the ship and the coupled ship motions (heave, roll and pitch). These are numerically solved for different initial conditions. An analysis of the dynamical behavior of the vessel with stabilization is presented in the form of numerical limits of stability, safe basins, integrity curves and integrity surfaces. Finally, curves of critical amplitude for different wave tunings are computed. A design procedure for quantitative assessment of the level of parametric rolling mitigation by means of ART’s is discussed.

Sensitivity Analysis in Parametric Rolling of a Modern Cruise Ship Using Numerical Simulations in 6-DOF

2020 ◽  
Author(s):  
Bülent Düz
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Simulations ◽  
Time Domain ◽  
Nonlinear Phenomenon ◽  
Cruise Ship ◽  
Parametric Roll ◽  
Parametric Rolling ◽  
Maximum Angle ◽  
Strip Theory ◽  
The Time Domain

Abstract Parametric roll is a nonlinear phenomenon that can result in large roll angles coupled with significant pitch motions. These motions might induce large loads on the ship structure, and compromise the safety of the crew and the cargo. The severity of the motions might reach to such levels that capsizing might occur. In this study sensitivity analysis in parametric rolling of a modern cruise ship is investigated using numerical simulations. Several parameters were considered as sources of uncertainty such as the combined effect of GM and roll radius of gyration, roll damping, ship speed, and fin characteristics. In terms of fin characteristics, fin angle rate and maximum angle, fin area and aspect ratio, and fin gains were investigated. Additionally, the non-ergodicity of parametric roll was studied as well as the effect of simulation duration on the statistics of parametric roll. The simulations were carried out with a hybrid time-domain seakeeping and manoeuvring code. The time-domain code was used in combination with a strip-theory based frequency-domain program in order to calculate diffraction and radiation forces as well as added-mass. The time-domain code was able simulate the dynamic behavior of a steered ship in 6-DOF, where the motions can be large up to the moment of capsize.

Parametric Rolling in Regular Head Waves of the KRISO Container Ship: Numerical and Experimental Investigation in Shallow Water

2019 ◽  
Author(s):  
Manases Tello Ruiz ◽  
Jose Villagomez ◽  
Guillaume Delefortrie ◽  
Evert Lataire ◽  
Marc Vantorre
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Water Waves ◽  
Failure Modes ◽  
Container Ship ◽  
Parametric Roll ◽  
Parametric Rolling ◽  
Wave Characteristics ◽  
Intact Stability ◽  
Head Waves

Abstract The IMO Intact Stability Code considers the parametric rolling phenomenon as one of the stability failure modes because of the larger roll angles attained. This hazardous condition of roll resonance can lead to loss of cargo, passenger discomfort, and even (in the extreme cases) the ship’s capsize. Studies as such are mostly conducted considering wave characteristics corresponding to wave lengths around one ship length (λ ≈ LPP) and wave amplitudes varying from moderate to rough values. These wave characteristics, recognised as main contributors to parametric rolling, are frequently encountered in deep water. Waves with lengths of such magnitudes are also met by modern container ships in areas in close proximity to ports, but with less significant wave amplitudes. In such areas, due to the limited water depth and the relatively large draft of the ships, shallow water effects influence the overall ship behaviour as well. Studies dedicated to parametric rolling occurrence in shallow water are scarce in literature. In spite of no accidents being yet reported in such scenarios, its occurrence and methods for its prediction require further attention; this in order to prevent any hazardous conditions. The present work investigates the parametric roll phenomenon numerically and experimentally in shallow water. The study is carried out with the KRISO container ship (KCS) hull. The numerical investigation uses methods available in literature to study the susceptibility and severity of parametric rolling. Their applicability to investigate this phenomenon in shallow water is also discussed. The experimental analysis was carried out at the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University). Model tests comprised a variation of different forward speeds, wave amplitudes and wave lengths (around one LPP). The water depth was fixed to a condition equivalent to a gross under keel clearance (UKC) of 100% of the ship’s draft.

Numerical Investigation of Parametric Rolling of a Container Ship in Regular and Irregular Waves

2017 ◽  
Author(s):  
Suresh Rajendran ◽  
C. Guedes Soares
Keyword(s):  
Incident Wave ◽  
Radiation Force ◽  
Wave Profile ◽  
Irregular Waves ◽  
Container Ship ◽  
Hydrodynamic Coefficients ◽  
Parametric Rolling ◽  
Nonlinear Radiation ◽  
Strip Theory ◽  
Radiation Forces

Parametric rolling of a post-Panamax C11 class containership in regular and irregular waves is numerically investigated using body nonlinear time domain methods based on strip theory. The Froude-Krylov and the hydrostatic forces are calculated for the exact wetted surface area under the undisturbed incident wave profile. Two kinds of formulations are used for calculation of the radiation forces. The first one employs a linear radiation force in which the frequency dependent hydrodynamic coefficients are calculated for mean position of the sections at mean water level. The second formulation calculates the hydrodynamic coefficients for the exact submerged depth of ship sections under the undisturbed incident wave profile, and hence called as body nonlinear radiation force. The numerical results from the aforementioned formulations are compared with each other, and also with experimental results obtained from a wave tank in both regular and irregular waves. For all the cases in regular waves, the vulnerability to parametric rolling is clearly identified by the numerical models, even though a few discrepancies are observed in the estimation of the severity (maximum roll angle) of the problem. In this paper, the effects of the linear and body nonlinear radiation forces on the numerical calculation of parametric rolling of a container ship and the ability of the numerical methods to identify parametric rolling are investigated.

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