Green water evolution on a fixed structure induced by incoming wave trains

2020 ◽  
pp. 1-29 ◽  
Author(s):  
Jassiel V. Hernández-Fontes ◽  
Irving D. Hernández ◽  
Edgar Mendoza ◽  
Rodolfo Silva
Keyword(s):  
Green Water ◽  
Incoming Wave ◽  
Wave Trains ◽  
Fixed Structure

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.

On the Generation of Isolated Green Water Events Using Wet Dam-Break

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Jassiel V. Hernández-Fontes ◽  
Marcelo A. Vitola ◽  
Monica C. Silva ◽  
Paulo de Tarso T. Esperança ◽  
Sergio H. Sphaier
Keyword(s):  
High Speed ◽  
Offshore Structures ◽  
Dam Break ◽  
Water Levels ◽  
Green Water ◽  
Incoming Wave ◽  
Aspect Ratios ◽  
Water Problem ◽  
Different Types ◽  
Wave Trains

Green water occurs when an incoming wave exceeds the freeboard and propagates onto the deck of naval/offshore structures, such as floating production storage and offloading units and platforms. This water can affect the integrity of facilities and equipment that are installed on the deck, compromise the safety of the crew, and affect the dynamic stability of the structure. Traditionally, wave trains have been used to study the green water problem, which is a good approach to analyzing consecutive green water events. However, to carry out systematic studies that allow local details to be identified for different types of green water, an alternative method is to study isolated events generated by a single incoming wave. The purpose of this paper was to experimentally investigate the generation of different types of isolated green water events using the wet dam-break (DB) approach as an alternative to generating the incoming wave. Tests were carried out in a rectangular tank with a fixed internal structure. Different freeboard conditions were tested for two aspect ratios of the wet DB (h0/h1=0.40 and 0.6). Conventional wave probes were used to measure the water levels in the tank, and a high-speed camera was set to capture details of the generated green water events. The results demonstrated the ability of this approach to represent different types of green water, similar to those obtained with unbroken regular waves in barge-shaped fixed structures, including DB, plunging-dam-break (PDB) and hammer-fist (HF).

Numerical Research on FPSOs With Green Water Occurrence

2009 ◽  
Vol 53 (01) ◽  
pp. 7-18
Author(s):  
Renchuan Zhu ◽  
Guoping Miao ◽  
Zhaowei Lin
Keyword(s):  
Three Dimensional ◽  
Green Water ◽  
Floating Body ◽  
Incoming Wave ◽  
Model Case ◽  
Floating Structures ◽  
Design And Optimization ◽  
Head Waves ◽  
Wave Heights ◽  
The Impact

Green water loads on sailing ships or floating structures occur when an incoming wave significantly exceeds freeboard and water runs onto the deck. In this paper, numerical programs developed based on the platform of the commercial software Fluent were used to numerically model green water occurrence on floating structures exposed to waves. The phenomena of the fixed floating production, storage, and offloading unit (FPSO) model and oscillating vessels in head waves have been simulated and analyzed. For the oscillating floating body case, a combination idea is presented in which the motions of the FPSO are calculated by the potential theory in advance and computional fluid dynamics (CFD) tools are used to investigate the details of green water. A technique of dynamic mesh is introduced in a numerical wave tank to simulate the green water occurrence on the oscillating vessels in waves. Numerical results agree well with the corresponding experimental results regarding the wave heights on deck and green water impact loads; the two-dimensional fixed FPSO model case conducted by Greco (2001), and the three-dimensional oscillating vessel cases by Buchner (2002), respectively. The research presented here indicates that the present numerical scheme and method can be used to actually simulate the phenomenon of green water on deck, and to predict and analyze the impact forces on floating structures due to green water. This can be of great significance in further guiding ship design and optimization, especially in the strength design of ship bows.

scholarly journals LONGSHORE CURRENT FORCING AT A BARRED BEACH

1988 ◽  
Vol 1 (21) ◽  
pp. 5 ◽  
Author(s):  
D.J. Whitford ◽  
E.B. Thornton
Keyword(s):  
Barrier Island ◽  
Tidal Range ◽  
Longshore Current ◽  
Incoming Wave ◽  
Island Formation ◽  
Outer Banks ◽  
Wave Trains

The FRF site is located along a 100-km unbroken stretch of barrier island formation known as North Carolina's "Outer Banks." There are no littoral barriers to perturbate incoming wave trains along the entire reach of shoreline. The site has a tidal range of 0.5 to 2.0 m and regular offshore bathymetry.

Measurement of Green Water on a 3D Structure

2009 ◽  
Author(s):  
Kusalika Ariyarathne ◽  
Kuang-An Chang ◽  
Richard Mercier
Keyword(s):  
Vertical Wall ◽  
3D Structure ◽  
Maximum Velocity ◽  
Breaking Waves ◽  
Velocity Fields ◽  
The Other ◽  
Green Water ◽  
Incoming Wave ◽  
Linear Distribution ◽  
The Waves

The present study investigates the velocity fields of plunging breaking waves impinging on a three-dimensional simplified ship-shape structure in a laboratory wave tank. Green water was generated as the waves break and overtop the structure. Bubble image velocimetry (BIV) was used to measure the velocity field of green water along the centerline of the deck. Two plunging wave conditions were tested and compared: one with waves impinging on the vertical wall of the structure at the initial still water level; the other with waves impacting on the horizontal deck surface. The velocity fields are quite different for the two cases even though the incoming wave heights and the wave periods are nearly identical. It was observed that the maximum horizontal velocity is higher for the case with waves compacting on the deck. The waves also passed the deck quicker than the other case. For both cases the profiles of the green water velocity shows a non-linear distribution with the maximum velocity occurring near the front of the water.

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.

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.

scholarly journals The Numerical Simulation of Green Water Loading Including Vessel Motions and the Incoming Wave Field

2005 ◽  
Author(s):  
K. M. Theresa Kleefsman ◽  
G. Erwin Loots ◽  
Arthur E. P. Veldman ◽  
Bas Buchner ◽  
Tim Bunnik ◽  
...  
Keyword(s):  
Height Function ◽  
Green Water ◽  
Navier Stokes ◽  
Ship Motions ◽  
Far Field ◽  
Incoming Wave ◽  
Local Flow ◽  
Water Loading ◽  
Irregular Wave ◽  
Propagation Properties

This paper presents results from simulation of green water loading including vessel motions. The simulation is performed through a domain decomposition: the far field and ship motions are calculated by potential theory and are used to simulate the local flow around the deck of an offshore floater using a Navier-Stokes solver. In the solver the free surface is displaced using a Volume of Fluid based method, improved by introducing a local height function. First, simulations of an irregular wave, where the velocities at the boundaries of the domain are prescribed using results of a linear diffraction code are performed in order to check wave propagation properties. Then, the same code is used to initiate the simulation of an FPSO in high waves, resulting in green water on the deck.

scholarly journals On the Evolution of Different Types of Green Water Events

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1148
Author(s):  
Jassiel V. H. Fontes ◽  
Irving D. Hernández ◽  
Edgar Mendoza ◽  
Rodolfo Silva ◽  
Eliana Brandão da Silva ◽  
...  
Keyword(s):  
Water Surface ◽  
Early Stage ◽  
Dam Break ◽  
Green Water ◽  
Wave Steepness ◽  
Wave Flume ◽  
Initial Stage ◽  
Different Types ◽  
Wave Trains ◽  
First Time

Green water events may present different features in the initial stage of interaction with the deck of a structure. It is therefore important to investigate the evolution of different types of green water, since not all the events interact with the deck at the same time. In this paper, the evolution of three types of green water events (dam-break, plunging-dam-break, and hammer-fist) are studied. The water surface elevations and volumes over the deck in consecutive green water events, generated by incident [wave trains in a wave flume, were analyzed using image-based methods. The results show multiple-valued water surface elevations in the early stage of plunging-dam-break and hammer-fist type events. Detailed experimental measurements of this stage are shown for the first time. The effect of wave steepness on the duration of the events, maximum freeboard exceedance, and volumes were also investigated. Although the hammer-fist type showed high freeboard exceedances, the plunging-dam-break type presented the largest volumes over the deck. Some challenges for further assessments of green water propagation are reported.

A Numerical Study on the Evolution of Random Seas With the Occurrence of Rogue Waves

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Zhuowei Zhou ◽  
Ningchuan Zhang ◽  
Guoxing Huang
Keyword(s):  
Numerical Study ◽  
Wave Model ◽  
Rogue Waves ◽  
Experimental Investigations ◽  
Random Wave ◽  
Initial State ◽  
Incoming Wave ◽  
Spectral Parameters ◽  
Excess Kurtosis ◽  
Wave Trains

Abstract Numerous numerical and experimental investigations show that rogue waves present much larger probabilities of occurrence than predicted by the linear random wave model, i.e., Gaussian distributed waves. The deviation from normal statistical events excites a continuous concern about rogue wave research. In this study, rogue waves under long-crested and narrow-banded wave trains are checked using the high-order spectral (HOS)-NST model. The JONSWAP wave spectra with random phases are selected as the initial state of the incoming wave trains. Different values of spectral parameters are chosen to reproduce different random sea states with different Benjamin–Feir index (BFI). Numerical results are compared with the classical experimental study and show good agreements. Statistical properties of rogue waves are recounted again within the analysis of exceedance distribution function (EDF) of wave heights and wave crests. Spectral changes are examined, and the monotonic increases with BFI are stressed. However, no bifurcations are observed for BFI near 1. For large BFI, quasi-resonance interactions dominate the wave nonlinearities, and the resulted dynamic excess kurtosis involves initially monotonic enhancement along with space, peaking at around 20–30 wavelengths, but stays at stably high-level values. The quasi-steady-state of dynamic excess kurtosis after full interaction of wave nonlinearities in time and space demonstrates a continuous emergence of rogue waves much more frequent than normality. The changes of excess kurtosis along x are complicated where BFI near 1 and the occurrence of rogue waves might be enhanced even for BFI slightly inferior to 1.

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