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

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.

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.

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.

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

2002 ◽  
Author(s):  
Carlos Guedes Soares ◽  
Ricardo 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 (FPSO) 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 analysed 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.

The Analysis and Application of Numerical Wave Tank Based on the Viscous Fluid

2010 ◽  
Author(s):  
Lei Yue ◽  
Zhiguo Zhang ◽  
Dakui Feng
Keyword(s):  
Three Dimensional ◽  
Wave Generation ◽  
Green Water ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Water On Deck ◽  
Impact Forces ◽  
Numerical Wave ◽  
The Impact ◽  
Shipping Water

The so-called numerical wave tank is to use a mathematical model to simulate the process of making waves and interaction between waves and structures. Shipping water occurs when the wave height exceeds the deck level of a floating vessel. A large amount of seawater flows down onto the deck. It damages deck equipment and causes even submergence. The water on deck is called “Green Water”, and it is dangerous for ships. It is of great significance to analyze and simulate wave and green water phenomenon. This paper developed a three-dimensional numerical wave tank and presented VOF method to deal with the movement with free surface, and then simulated process of wave generation numerically. A two-dimensional numerical simulation of the green water phenomenon of a hull placed in regular wave was performed. The process of wave running up and wave deforming were obtained. The results show that the present numerical scheme and methods can be used to simulate process of wave generation and phenomenon of green water on deck, and to predict and analyze the impact forces between waves and structures due to green water.

Towards an Improved Understanding of Green Water Exceedance at the Bow of an FPSO

2016 ◽  
Author(s):  
Riaan van ‘t Veer ◽  
Anne Boorsma
Keyword(s):  
Model Test ◽  
Weather Conditions ◽  
Model Tests ◽  
Present Problem ◽  
Green Water ◽  
Detailed Model ◽  
Water Flows ◽  
Water On Deck ◽  
Dam Breaking ◽  
Flooding Events

When a permanently moored FPSO in deep draft condition finds itself in harsh weather conditions it most likely will experience freeboard exceedance at the bow and consequently green water on deck. Knowledge about how and how much water will come onto the deck, is relevant for both a turret moored and spread-moored FPSO since both are expected to experience the most severe design conditions in head to bow quartering waves. In this paper we focus on green water phenomena observed on a Suezmax FPSO in severe head seas in the model test basin. Using an on-board video in combination with deck-mounted wave probes, green water events are recorded in detail. This provides unique insights in how the water floods onto the deck. Very different flooding phenomena are observed between different events and they can strongly deviate from a dam-breaking kind of event. Through a detailed description of three typical flooding events, the present paper improves the understanding of how green water flows onto the deck. It highlights the benefit of detailed model tests and emphasizes that new and more detailed modelling is required since the dam-breaking theory has limited value for the present problem.

A Quasi-three-dimensional Finite-volume Shallow WaterModel for Green Water on Deck

2013 ◽  
Vol 57 (3) ◽  
pp. 125-140 ◽  
Author(s):  
Daniel A. Liut ◽  
Kenneth M. Weems ◽  
Tin-Guen Yen
Keyword(s):  
Finite Volume ◽  
Three Dimensional ◽  
Green Water ◽  
Water On Deck

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.

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