Green Water Loads Determination for FPSO Exposed to Beam Sea Conditions

2014 ◽  
Author(s):  
Daniel Fonseca de Carvalho e Silva ◽  
Ronaldo Rosa Rossi
Keyword(s):  
Careful Analysis ◽  
Dam Break ◽  
Green Water ◽  
Cfd Simulations ◽  
Water On Deck ◽  
Special Boundary Condition ◽  
Global Result ◽  
Exploration And Production ◽  
Loads Analysis ◽  
Water Elevation

Considering new offshore frontiers for oil exploration and production, specially the Santos Basin region, FPSOs will be exposed to more severe wave conditions. This scenario requires careful analysis with respect to the green water phenomenon. The complex physics involved in the water-on-deck flow implies on several uncertainties regarding green water loads analysis. Taking into account model tests, CFD simulations and analytical formulations, this paper aims to simplify the green water loads determination, proposing a methodology to estimate these loads considering the water elevation above deck measured from experiments or numerical tools. In order to accomplish this objective, CFD simulations with different solvers were run for a benchmark case, showing that it is a suitable approach for a global result in impact dam break cases. After that, a special boundary condition was calibrated to represent model test results of water propagation in a FPSO deck exposed to beam sea in terms of water elevation. Using this CFD model, the loads on exposed structures was determined and compared against the dam break analytical formulation, which was modified to take into account the gap between each structure and the deck. Finally some vane type protection structures were simulated and their efficiency in partially obstructing the water-on-deck flow was evaluated. As a global result from all these analysis, a more comprehensive strategy for green water loads determination is proposed.

Using a Simplified Smoothed Particle Hydrodynamics Model to Simulate Green Water on the Deck

2012 ◽  
Author(s):  
Csaba Pakozdi ◽  
Carl-Trygve Stansberg ◽  
Paal Skjetne ◽  
Wei Yang
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Diffraction Theory ◽  
Green Water ◽  
Test Time ◽  
Random Wave ◽  
Water On Deck ◽  
Simulation Speed ◽  
Slamming Load ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

Severe storms have gained more attention in recent years. Improved metocean data have led to new insight into severe wave conditions for marine design. Therefore, there exists an industrial demand for fast and accurate numerical tools to estimate the hydrodynamic loads during e.g. green water events. Model tests generally play an important role in these studies. In the recent past, several practical engineering tools have also been developed, based on the experience from the experimental data bases in combination with simplified but still theoretical formulations. One such tool is Kinema2, which is based on non-linear random wave modeling combined with 3D linear diffraction theory to initially identify green water events, and then finally apply a simplified water-on-deck and slamming load estimation. This forms the background for the work presented in this paper which shows the feasibility of a new technique based on the Smoothed Particle Hydrodynamics (SPH). This method can give more detailed forecast of the hydrodynamics on the deck than the simplified water-on-deck estimation. SPH uses a Lagrangian framework (particles) to describe the fluid dynamics. The water propagation and kinematics of the green water events are, in this introductory stage of the study, reproduced by using a SPH inlet condition where particles are injected with given velocity from a curved rectangular area against the deck and the deckhouse. The relative wave height and water particle velocities found from KINEMA2. Numerical results for water elevation and velocity on deck are compared against model test time series and previous results from other numerical simulation methods. The present Lagrangian nature (compared to traditional Eulerian-VOF methods) can in principe significantly reduce the CPU demand and increase the simulation speed. Slamming pressures can then be calculated e.g. from simple slamming formula calculations. In principle, pressures can also be found directly from the SPH calculations, while this would demand a significantly larger number of particles which increases CPU demand of the SPH method.

Green water loads using the wet dam-break method and SPH

2021 ◽  
Vol 219 ◽  
pp. 108392
Author(s):  
Omar S. Areu-Rangel ◽  
Jassiel V. Hernández-Fontes ◽  
Rodolfo Silva ◽  
Paulo T.T. Esperança ◽  
Jaime Klapp
Keyword(s):  
Dam Break ◽  
Green Water

Significant load and green water on deck of offshore units/vessels

1998 ◽  
Vol 25 (8) ◽  
pp. 715-731 ◽  
Author(s):  
B. Hamoudi ◽  
K.S. Varyani
Keyword(s):  
Green Water ◽  
Water On Deck

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.

scholarly journals Green Water on A Fixed Structure Due to Incident Bores: Guidelines and Database for Model Validations Regarding Flow Evolution

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2584 ◽  
Author(s):  
Jassiel V. Hernández-Fontes ◽  
Paulo de Tarso T. Esperança ◽  
Juan F. Bárcenas Graniel ◽  
Sergio H. Sphaier ◽  
Rodolfo Silva
Keyword(s):  
High Speed ◽  
Temporal Distribution ◽  
Dam Break ◽  
Green Water ◽  
Two Dimensional ◽  
High Resolution Data ◽  
Water Elevations ◽  
Fixed Structure ◽  
Flow Propagation ◽  
Air Cavities

This paper presents a two-dimensional experimental study of the interaction of wet dam-break bores with a fixed structure, regarding the evolution of the incident flows and the resultant green water events on the deck. The study employs image-based techniques to analyse flow propagation from videos taken by high-speed cameras, considering five different shipping water cases. The features of small air-cavities formed in some green water events of the plunging-dam-break type were analysed. Then, the spatial and temporal distribution of water elevations of the incident bores and green water were investigated, providing a database to be used for model validations. Some guidelines for the selection of the freeboard exceedance, which is of relevance for green water simulations, were provided. Finally, the relationship between the incident bore and water-on-deck kinematics was discussed. The proposed study can be used as a reference for performing simplified and systematic analyses of green water in a different two-dimensional setup, giving high-resolution data that visually capture the flow patterns and allow model validations to be performed.

Experimental Study of the Probability Distributions of Green Water on the Bow of Floating Production Platforms

2004 ◽  
Vol 127 (3) ◽  
pp. 234-242 ◽  
Author(s):  
C. Guedes Soares ◽  
R. Pascoal
Keyword(s):  
Experimental Study ◽  
Conditional Distribution ◽  
Probability Distributions ◽  
Green Water ◽  
Experimental Program ◽  
Separate Analysis ◽  
Response Process ◽  
Water On Deck ◽  
Distribution Water ◽  
Water Height

Results of an experimental program with a model of a moored floating production storage and offloading vessel are used to study the probability distributions associated with various phenomena related with green water loading. Separate analysis of wave height and crests are performed in order to assess the presence and significance of nonlinearities. Time series of pitch motion and relative motion are analyzed to check for linearity of the response process. Probability distributions of the occurrence of water on deck and of the conditional distribution water height above deck are also studied.

scholarly journals Study on Green Water of Tumblehome Hull Using Dam-Break Flow and Ranse Models

2017 ◽  
Vol 24 (s2) ◽  
pp. 172-180
Author(s):  
Shuzheng Sun ◽  
Wenlei Du ◽  
Hui Li
Keyword(s):  
Numerical Simulation ◽  
Cfd Simulation ◽  
Wave Interaction ◽  
Simulation Method ◽  
Dam Break ◽  
Green Water ◽  
Nonlinear Phenomenon ◽  
Numerical Simulation Methods ◽  
Dam Break Flow ◽  
Water Problems

Abstract The tumblehome hull adopts some novelty designs such as low-tumblehome freeboard and wave-piercing bow. The new form design makes the ship have many special hydrodynamic performances. Especially the green water of tumblehome hull is different from that of hulls with flare free board. Green water is a strong nonlinear phenomenon of ship-wave interaction, the variation of free surface of liquid is complicated, and there are still some difficulties to solve green water problems well with numerical simulation method. In this paper firstly the motion responses of the tumblehome hull was calculated based on 3D potential theory, and then the dam-break flow model was used to calculate green water height and pressure distribution. According to the result of numerical simulation, some typical working conditions are chosen for 3D CFD simulation using RANS method. The results of numerical simulation methods are compared with the experimental results measured in towing tank. The influence of different ship form parameters and wave parameters to the green water of tumblehome hull is analyzed, and some regularities of green water on tumblehome hull in regular waves are summarized.

Shipping of water on a two-dimensional structure. Part 2

2007 ◽  
Vol 581 ◽  
pp. 371-399 ◽  
Author(s):  
M. GRECO ◽  
G. COLICCHIO ◽  
O. M. FALTINSEN
Keyword(s):  
Three Dimensional ◽  
Quantitative Information ◽  
Front Velocity ◽  
Green Water ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Incoming Wave ◽  
Water On Deck ◽  
Type Water ◽  
Water Front

The water-shipping problem is modelled in a two-dimensional framework and studied experimentally and numerically for the case of a fixed barge-shaped structure. The analysis represents the second step of the research discussed in Greco et al. (J. Fluid Mech., vol. 525, 2005, p. 309). The numerical investigation is performed by using both a boundary element method and a domain-decomposition strategy. The model tests highlight the occurrence of dam-breaking-type water on deck, (a) with and (b) without an initial plunging phase, and (c) an unusual type of water shipping connected with blunt water–deck impacts here called a hammer-fist type event never documented before. Cases (a) and (c) are connected with the most severe events and the related features and green-water loads are discussed in detail. A parametric analysis of water-on-deck phenomena has also been carried out in terms of the local incoming waves and bow flow features. We classify such phenomena in a systematic way to provide a basis for further investigations of water-on-deck events. The severity of (a)-type water-on-deck events is analysed in terms of initial cavity area and water-front velocity along the deck. The former increases as the square power of the modified incoming-wave (front-crest) steepness while the latter scales with its square-root. The two-dimensional investigation gives useful quantitative information in terms of water-front velocity for comparison with three-dimensional water-on-deck experiments on fixed bow models interacting with wave packets.

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