Prediction of Ship Response Statistics in Severe Sea Conditions Using RANS

2012 ◽  
Author(s):  
Jan Oberhagemann ◽  
Jens Ley ◽  
Bettar Ould el Moctar
Keyword(s):  
Structural Design ◽  
International Association ◽  
Rayleigh Distribution ◽  
Ship Motions ◽  
Wave Loads ◽  
Large Wave ◽  
Hull Girder ◽  
New Methods ◽  
Design Loads ◽  
Wave Induced

The International Association of Classification Societies (IACS) promotes the paradigm shift in structural design rules for ships towards risk based approaches. This requires improvements in the assessment of structural design loads and new methods for estimation of wave loads and responses, amongst others with respect to extreme value distributions. In this paper we present a numerical method based on the solution of RANS equations to deal with large wave-induced ship motions and corresponding loads for different ship types. Nonlinearities of wave excitation and ship response are included. Short-term ship response distributions from time domain simulations are compared with model test data. Significant deviations from Rayleigh distribution of amplitudes are observed, especially for hull girder loads including effects of structural elasticity.

Numerical Analysis of Ship Wave Loads and Structure Strengthen Analysis on a Wind Power Installation Ship

2011 ◽  
Vol 90-93 ◽  
pp. 2521-2527
Author(s):  
Gang Qiang Li ◽  
Yan Yan Zhao ◽  
Yong He Xie
Keyword(s):  
Wind Power ◽  
Structural Design ◽  
Three Dimensional ◽  
Load Condition ◽  
Wave Loads ◽  
Element Simulation ◽  
Wind Power Installation ◽  
Wave Induced ◽  
Term Response

In a typical load condition of wind power equipment Installation ship, using the three-dimensional potential flow theory to prediction the long-term response of wave induced loads. then using the main load control parameters as a basis for the design wave selection, then application of DNV's SESTRA program make the wave-induced directly to the structure to finite element simulation. The results show that the hull structural design can meet the requirements.

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.

On the Computation of Wave Induced Bending and Torsion Moments

1971 ◽  
Vol 15 (03) ◽  
pp. 217-220
Author(s):  
T. Francis Ogilvie
Keyword(s):  
Boundary Value Problem ◽  
Boundary Value ◽  
Diffraction Problem ◽  
Vertical Plane ◽  
Bending Moment ◽  
Ship Motions ◽  
Wave Loads ◽  
Cross Member ◽  
Wave Induced ◽  
Incident Waves

In the calculation of wave loads on a ship, one must consider the effects of both the incident waves and the diffraction waves (the latter being caused by the presence of the ship in the incident waves). In the ship-motions problem, Khaskind showed how one can do this without having to solve the diffraction-wave boundary-value problem. Khaskind's procedure is here extended to the calculation of structural loads on a ship. Two examples are discussed: (i) bending moment in the vertical plane of a ship in waves and (ii) torsion in the cross member of a catamaran. Many other applications are possible. In each case, it is necessary to solve a boundary-value problem, but it is generally much simpler than the diffraction problem.

scholarly journals Improvement of the Ship Emergency Response Procedure in Case of Collision Accident Considering Crack Propagation during Salvage Period

2021 ◽  
Vol 9 (7) ◽  
pp. 737
Author(s):  
Ivana Gledić ◽  
Antonio Mikulić ◽  
Joško Parunov
Keyword(s):  
Crack Propagation ◽  
Emergency Response ◽  
Software Tool ◽  
Fatigue Loading ◽  
Rayleigh Distribution ◽  
Crack Size ◽  
Initial Crack ◽  
Stiffened Panel ◽  
Wave Loads ◽  
Hull Girder

Specialized procedures to help in the emergency response situations following ship accidents have been under development by the Classification Societies. Such procedures consider the hull-girder collapse as the most important failure mode, without the possibility of crack propagation caused by fluctuating wave loads. In the present study, the fatigue crack propagation in the main deck of the oil tanker damaged in collision during salvage is investigated. The shape and size of the damage are modelled using the realistic bow shape of the striking ship and historical data of ship accidents. The stress intensity factor (SIF) across the main deck of the struck ship is calculated numerically and by the method based on the available experimental results of the crack propagation in the stiffened panel. Fluctuating wave–induced stresses in short-term sea conditions during salvage are obtained by Monte Carlo simulation (MC) based on Rayleigh distribution. Cycle-by-cycle crack propagation is calculated using Paris law. Many salvage simulations are performed to cover different possible time-histories of the fatigue loading. Results of the analysis are presented as histogram of the crack increase during salvage. Parametric analysis is performed to investigate the influence of the sea state severity, initial crack size, and towing duration on the final crack size. The proposed procedure can be considered as a part of a software tool for emergency response action during salvage of damaged ship.

An Approach to the Estimation of Structural Design Loads of Turret Moored FPSO Tankers

2003 ◽  
Author(s):  
Huilong Ren ◽  
Chang Doo Jang
Keyword(s):  
Structural Design ◽  
Three Dimensional ◽  
Wave Loads ◽  
Short Term ◽  
Efficient Calculation ◽  
Restoring Forces ◽  
Design Loads ◽  
The Given ◽  
Equations Of Motions

A practical approach to determine the structural design loads of turret moored FPSO (Floating Production Storage and Offloading) tankers is suggested in this paper. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory. The effect of the restoring forces is included in the equations of motions of the ship in the form of linear stiffness coefficients. The hydrodynamic coefficients are calculated by the three-dimensional potential flow theory. The equations of motions are solved in frequency domain, and the motions and wave loads responses can be obtained. Then the short-term and long-term analyses are carried out for the wave loads of this kind of ship. With a 250m turret moored FPSO tanker as an example, according to the given environmental sea states data, headings, exceeding probability for the FPSO tanker, the structural design loads are calculated and compared with those obtained from rules for traditional tankers with the same dimensions. By the present approach, it is possible to perform a practical and efficient calculation of structural design loads of actual turret moored FPSO tankers.

Improving the Panel-Free Method for the Prediction of Ship Motions and Wave Induced Loads

2017 ◽  
Author(s):  
Wei Qiu ◽  
Heather Peng ◽  
Junshi Wang ◽  
Shahriar Nizam
Keyword(s):  
Simple Algorithm ◽  
Design Stage ◽  
Ship Motions ◽  
Wave Loads ◽  
Forward Speed ◽  
Early Design Stage ◽  
B Splines ◽  
Frequency Domain Methods ◽  
Nurbs Surfaces ◽  
Wave Induced

Frequency-domain methods are proven efficient and reliable, especially for zero forward speed, in early design stage for the prediction of ship motions and wave-induced wave loads. There are still challenges for ships with forward-speed due to the inaccuracy in the computation of m-terms. In this paper, the panel-free method is further improved to predict motions and wave-induced loads on real ships with forward speeds. A simple algorithm has been developed to re-arrange the control points for Non-Uniform Rational B-Splines (NURBS) surfaces. This method led to reliable and accurate m-term computations and therefore improved ship motion and load predictions. Validation studies have been carried out for a hydroelastic model of a frigate. Computed motions and loads were compared with experimental data.

Minimum Structure for Well Appraisal in Marginal Fields at 35m Water Depth without Jacket & Mudline Suspension System

2021 ◽  
Author(s):  
Prabir Kumar Chatterjee
Keyword(s):  
Structural Design ◽  
Dynamic Effect ◽  
Well Testing ◽  
Wave Loads ◽  
Environmental Loads ◽  
High Wave ◽  
Drilling Rig ◽  
Mat Foundations ◽  
Wave Induced ◽  
Reserve Strength

ABSTRACT This paper proposes a minimum structure for drilling two appraisal wells. Conductors will be driven into seabed by a crane vessel or drilling-rig crane through a pre-installed lightweight guide-frame placed on seabed. After driving the conductors to required depth, the frame is raised and joined to the conductors at appropriate elevation by bolted and grouted connections. Six tie members connected between the frame and seabed by specially-designed small mat foundations will ensure stability of the structure against environmental loads. A small deck will be installed on the top of conductors to provide space for essential equipment required for prolonged well testing after departure of drilling rig. The platform will be accessed by small boats through a boat landing and ladder. In case of positive drilling outcome, a riser and flexible pipeline will be added to connect with the nearest subsea tie-in point. A detailed structural design of the minimum facility is performed to withstand omnidirectional environmental loads due to 10.0m high wave along with associated wind and current loads. Susceptibility of the structure against dynamic effect of wave loads is also investigated. Demonstration of structural adequacy against wave-induced fatigue loads and reserve strength against extreme environmental loads show the robustness of the minimum structure to perform against design environmental loads.

scholarly journals WAVE LOADS ON EXPOSED JETTIES: DESCRIPTION OF LARGE SCALE EXPERIMENTS AND PRELIMINARY RESULTS

2011 ◽  
Vol 1 (32) ◽  
pp. 18 ◽  
Author(s):  
Luca Martinelli ◽  
Alberto Lamberti ◽  
Maria Gabriella Gaeta ◽  
Matteo Tirindelli ◽  
John Alderson ◽  
...  
Keyword(s):  
Large Scale ◽  
Research Team ◽  
Scale Effects ◽  
Wave Loads ◽  
Large Wave ◽  
Preliminary Results ◽  
Wave Flume ◽  
Air Content ◽  
Wave Induced ◽  
The Impact

The large scale experiments described in this paper were carried out at the Large Wave Flume (GWK, Große Wellenkanal) in Hanover (Germany). The research team included Universities of Bologna (IT), Edinburgh (UK), Southampton (UK), Plymouth (UK), HR Wallingford (UK) and Coast & Harbor Engineering Inc (USA). Wave-induced loads on close-to-prototype scale jetties were measured, with particular attention to scale effects due to air content in water. The aim of the paper is to present the tests, describe the impact process and give preliminary results concerning uplift loads.

Consideration of Wave-Induced Loads for Direct Strength Calculation Under Extreme Waves

2002 ◽  
Author(s):  
Tingyao Zhu ◽  
Atsushi Kumano ◽  
Toshiyuki Shigemi ◽  
Ryoju Matsunami
Keyword(s):  
Extreme Values ◽  
Correction Method ◽  
Exceedance Probability ◽  
Ship Motions ◽  
Nonlinear Phenomenon ◽  
Extreme Waves ◽  
Hull Girder ◽  
Bulk Carriers ◽  
Wave Induced

Relationship between extreme values in long-term distribution and the short-term values under each sea-state in which ships may encounter through their lifetime is discussed regarding wave-induced loads such as ship motions, hull girder moments and hydrodynamic pressures. Based on the discussion, a simplified formula of the wave-induced loads equivalent to the extreme value in the long-term distribution at the exceedance probability of 10−8 is proposed together with the corresponding sea-states by a series of direct load analyses of the tankers and bulk carriers. Furthermore, nonlinear characteristics with respect to waveheight on wave-induced loads are discussed based on the comprehensive experiment results of a blunt ship model in regular/irregular extreme waves. Finally, a correction method of the observed nonlinear phenomenon is proposed.

Sensor-Based Structural Health Monitoring for Marine and Offshore Structures

2021 ◽  
Author(s):  
Bo Wang ◽  
Meng-Lung Liu ◽  
Yong Chen
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Structural Response ◽  
Offshore Structures ◽  
Superposition Method ◽  
Wave Loads ◽  
Hull Girder ◽  
Structural Health ◽  
Load Distributions ◽  
Wave Induced

The objective of this study is to develop the sensor-based structural health monitoring (SHM) system using a reduced order model (ROM) wherein a modal superposition method is implemented to reconstruct hull girder load distributions of the entire structure under wave-induced loads. Seakeeping and finite element (FE) analyses are performed to obtain the structural response for various wave conditions. A set of specific wave headings and frequencies is selected to construct base wave modes, and the structural response can be reconstructed under arbitrary wave loads. Case studies using a containership and an FPSO have been conducted to verify this new methodology.

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