A Design Methodology For Green Water Loading On Ship-Type offshore Structures

2005 ◽  
Author(s):  
E J Ballard ◽  
◽  
A J Fyfe ◽  
Keyword(s):  
Design Methodology ◽  
Offshore Structures ◽  
Green Water ◽  
Water Loading

Toward Limit State Design of Ships and Offshore Structures Under Impact Pressure Actions: A State-of-the-Art Review

2006 ◽  
Vol 43 (03) ◽  
pp. 135-145
Author(s):  
Jeom Kee Paik
Keyword(s):  
Limit State ◽  
Structural Response ◽  
Time History ◽  
Rate Sensitivity ◽  
Offshore Structures ◽  
Impact Pressure ◽  
Green Water ◽  
Limit State Design ◽  
Structural Capacity ◽  
Pressure Time

In design of ships and ship-shaped offshore units, issues related to impact pressure actions arising from sloshing, slamming, green water, or explosion are of particular concern. The structural response under impact pressure actions is quite different from that under static or quasistatic actions. It has been recognized that the limit state approach is a more rational basis for structural design and safety assessment where both "demand" (loads) and "capacity" (strength) must be accurately defined. For impact pressure action cases, the demand is associated with hydrodynamics areas, taking into account the characteristics of impact pressure-time history, and the structural capacity is associated with structural mechanics areas, considering geometric and material nonlinearities together with strain rate sensitivity. This paper reviews recent advances and trends toward future limit state design of ships and offshore structures under impact pressure actions.

Design Aspects of Green Water Loading on FPSOs

2003 ◽  
Author(s):  
Bas Buchner ◽  
Joaqui´n Lopez-Cortijo Garcia
Keyword(s):  
Evaluation Method ◽  
Offshore Structures ◽  
Green Water ◽  
Evaluation Procedure ◽  
Design Evaluation ◽  
Water Impact ◽  
Advantages And Disadvantages ◽  
Water Problem ◽  
Semi Empirical ◽  
Empirical Design

Green water is a significant problem for floating ship-type offshore structures, which needs to be assessed in the early design of the structure. First the present paper summarises a new semi-empirical design evaluation procedure that can assist in this design process. Then the practical design considerations related to the green water problem are discussed. There are different ways to solve the green water problem for a particular structure at a specific location: • Design the vessel and structures on the deck against the predicted green water impact load levels. • Optimise the bow shape (underwater shape and above water bow flare). • Increase the freeboard height such that green water is prevented completely. • Increase the freeboard height such that the green water loads are reduced to acceptable levels and design for these load levels. • Optimise the structures on the deck to minimise the green water impact loads. • Use protecting breakwaters in front of critical structures on the deck. All these options have their advantages and disadvantages. The semi-empirical design evaluation method and the different design options are discussed in a case study, focussing on a new DP FPSO concept.

Loads on Ships and Offshore Structures

2007 ◽  
Author(s):  
P. Temarel
Keyword(s):  
State Of The Art ◽  
Fatigue Loading ◽  
Rogue Waves ◽  
Offshore Structures ◽  
Green Water ◽  
Vortex Induced Vibrations ◽  
Ice Loads ◽  
Offshore Industry ◽  
Multi Body ◽  
Wave Induced

The Loads Committee of the International Ship and Offshore Structures Congress (ISSC) critically reviews the state of the art of environmental and operational loads. Amongst these, elements more relevant to the offshore industry will be presented in this paper. These comprise wave-induced loads, including linear and nonlinear methods, multi-body interactions, slamming, green water, sloshing and rogue waves, cables and risers, vortex-induced vibrations, ice loads, fatigue loading and, verification and validation.

Use of Wet Dam-Break to Study Green Water Problem

2017 ◽  
Author(s):  
Jassiel V. Hernández-Fontes ◽  
Marcelo A. Vitola ◽  
Monica C. Silva ◽  
Paulo de Tarso T. Esperança ◽  
Sergio H. Sphaier
Keyword(s):  
High Speed ◽  
Good Practice ◽  
Offshore Structures ◽  
Dam Break ◽  
Irregular Waves ◽  
Green Water ◽  
Incoming Wave ◽  
Water Problem ◽  
Different Types ◽  
Fixed Structure

Green water occurs when an incoming wave exceeds the freeboard and propagates on the deck of naval/offshore structures, such as FPSO’s and platforms. The water on deck can affect the integrity of facilities and equipments installed on it, compromise the safety of the crew and affect the dynamic stability of the structure. Traditionally, regular or irregular waves generated by different types of wave-makers have been used to reproduce green water events. This is a good practice to study consecutive events. However, to study isolated events, an alternative could be the use of the wet dam-break approach to generate the incoming flow. The purpose of this paper is to investigate experimentally the use of the wet dam-break approach to generate isolated green water events. Tests were carried out in a rectangular tank with a fixed structure. Different freeboard conditions were tested for one aspect ratio of the wet dam-break (h0/h1 = 0.6). High speed cameras were used to investigate the initial phases of green water. Results demonstrated the ability of this approach to represent different types of green water events.

Effective and Efficient Breakwater Design for Trading Vessels and FPSOs

2006 ◽  
Author(s):  
Kamlesh Varyani ◽  
Trevor Hodgson ◽  
Xuan Pham
Keyword(s):  
Cost Effective ◽  
Green Water ◽  
Design Criteria ◽  
Forward Speed ◽  
Water Loading ◽  
Supporting Structure ◽  
Horizontal Loading ◽  
Double Skin

Breakwaters obviously need to fulfil their function (protecting sensitive structures or cargo) while at the same time remaining intact and imposing manageable loads onto supporting structure. It goes without saying that such breakwaters should be cost effective, so that complex designs with extensive welding may not be preferable. In this paper the authors will discuss green water loading on breakwaters for trading vessels like container ships which have forward speed and FPSOs which have zero speed. Different generic designs of V shape, vane type, double skin with and without holes and forward sloping forecastle (whaleback deck) breakwaters applied to trading vessels will be discussed. Guidelines for modelling green water horizontal loading on breakwaters of FPSOs and trading vessels using CFD techniques will be provided. The paper will also include a review of breakwater design criteria in rules and regulations.

Green Water Loading on a FPSO

2002 ◽  
Vol 124 (2) ◽  
pp. 97-103 ◽  
Author(s):  
O. M. Faltinsen ◽  
M. Greco ◽  
M. Landrini
Keyword(s):  
Nonlinear Effects ◽  
Rigid Wall ◽  
Green Water ◽  
Ship Motions ◽  
Sea Waves ◽  
Coupled Flow ◽  
Local Flow ◽  
Water Loading ◽  
Dam Breaking ◽  
The Impact

Green Water Loading in the bow region of a Floating Production Storage and Offloading unit (FPSO) in head sea waves is studied by numerical means. A 2-D method satisfying the exact nonlinear free-surface conditions within potential-flow theory has been developed as a step towards a fully 3-D method. The flow is assumed 2-D in a plane containing the ship’s centerplane. The method is partly validated by model tests. The importance of environmental conditions, 3-D flow effects, ship motions, and hull parameters are summarized. The wave steepness of the incident waves causes important nonlinear effects. The local flow at the bow is, in general, important to account for. It has become popular to use a dam-breaking model to study the propagation of water on the deck. However, the numerical studies show the importance of accounting for the coupled flow between the deck and outside the ship. When the water is propagating on the deck, a suitable distance from the bow can be found from where shallow-water equations can be used. Impact between green water on deck and a vertical deck-house side in the bow area is studied in details. A similarity solution for impact between a wedge-formed water front and a vertical rigid wall is used. Simplified solutions for an impacting fluid wedge with small and large interior angles are developed, both to support the numerical computations and to provide simpler formulas of practical use. It is demonstrated how the local design of the deck house can reduce the slamming loads. The importance of hydroelasticity during the impact is discussed by using realistic structural dimensions of a deck house. This indicates that hydroelasticity is insignificant. On the contrary, first results from an ongoing experimental investigation document blunt impacts against the deck during the initial stage of water shipping, which deserve a dedicated hydroelastic analysis.

Prediction of Green Water and Wave Loading Using a Navier-Stokes Based Simulation Tool

2002 ◽  
Author(s):  
K. M. Theresa Kleefsman ◽  
Geert Fekken ◽  
Arthur E. P. Veldman ◽  
Tim H. J. Bunnik ◽  
Bas Buchner ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Height Function ◽  
Offshore Structures ◽  
Green Water ◽  
Navier Stokes ◽  
Wave Loading ◽  
Navier Stokes Equations ◽  
Sensitivity Tests ◽  
Incompressible Viscous Fluids ◽  
Volume Method

Results of computer simulation of wave and green water loading on floating offshore structures are presented. The simulation program used is a CFD code which solves the Navier-Stokes equations that describe flow of incompressible viscous fluids. The Navier-Stokes equations are discretised using a Finite Volume method on a Cartesian grid with staggered variables. The free surface is displaced using a Volume Of Fluid based algorithm combined with a local height function. In this paper results of validation and sensitivity tests of simulation of green water on the foredeck of an FPSO are presented. Here, the waves are modeled as a dam of water around the deck which is suddenly released. Furthermore, wave loading from impact of regular waves on a SPAR platform is computed and compared with experimental results. The program is found to be robust and the computational results show good agreement with the experiments.

Effective and Efficient Breakwater Design for Trading Vessels and FPSOS

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Kamlesh Varyani ◽  
Trevor Hodgson ◽  
Xuan Pham
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cost Effective ◽  
Green Water ◽  
Design Criteria ◽  
Forward Speed ◽  
Water Loading ◽  
Supporting Structure ◽  
Double Skin ◽  
Computational Fluid Dynamics Cfd

Breakwaters obviously need to fulfill their function (protecting sensitive structures or cargo) while at the same time remaining intact and imposing manageable loads onto supporting structure. It goes without saying that such breakwaters should be cost effective, so that complex designs with extensive welding may not be preferable. In this paper the authors discuss green water loading on breakwaters for trading vessels like container ships which have forward speed and FPSOs which have zero speed. Different generic designs of V shape, vane type, double skin with and without holes, and forward sloping forecastle (whaleback deck) breakwaters applied to trading vessels are discussed. Guidelines for modeling green water horizontal loading on breakwaters of FPSOs and trading vessels using computational fluid dynamics (CFD) techniques are provided. The paper will also include a review of breakwater design criteria in rules and regulations.

Numerical Investigation of the Effect due to Vessel Motion on Green Water Impact on Deck

2017 ◽  
Author(s):  
Ravindra Babu Kudupudi ◽  
Ranadev Datta
Keyword(s):  
Green Water ◽  
Global Motion ◽  
Cfd Model ◽  
Water Impact ◽  
Water Loading ◽  
Motion Effect ◽  
Heading Angle ◽  
Vessel Motion ◽  
Volume Method ◽  
The Impact

The present paper focuses on modeling of green water loading on an oscillating body using CFD. The vessel motion is calculated a priory using time domain panel method code, then green water impact is computed based on that pre-calculated motion. The finite volume method is used to capture the green water impact, however in order to represent the free surface, volume of fluid method is used. A sophisticated dynamic mesh is used to handle the motion of the vessel in fluid domain. Several examples and case studies are considered to validate the present CFD model as well as to check the effect of global motion on green water loading such as effect of steepness and heading angle on green water impact. Results show that due to the motion, the impact loading phenomena changes significantly and there is a significant change in pressure on the deck after considering the motion effect and it deviates considerably with the results obtained from fixed vessel cases.

Sign in / Sign up

Export Citation Format

Share Document