Assessing shipping water vertical loads on a fixed structure by convolution model and wet dam-break tests

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.

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

Water ◽

10.3390/w11122584 ◽

2019 ◽

Vol 11 (12) ◽

pp. 2584 ◽

Cited By ~ 7

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.

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A CFD Numerical Study to Evaluate the Effect of Deck Roughness and Length on Shipping Water Loading

Water ◽

10.3390/w13152063 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2063

Author(s):

Paola E. Rodríguez-Ocampo ◽

Jassiel V. H. Fontes ◽

Michael Ring ◽

Edgar Mendoza ◽

Rodolfo Silva

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Numerical Investigation ◽

Numerical Study ◽

Numerical Approach ◽

Structural Elements ◽

Marine Structures ◽

Order Of Magnitude ◽

Fixed Structure ◽

Shipping Water

Shipping water events that propagate over the decks of marine structures can generate significant loads on them. As the configuration of the structure may affect the loading behaviour, investigation of shipping water loads in different structural conditions is required. This paper presents a numerical investigation of the effect of deck roughness and deck length on vertical and horizontal loads caused by shipping water on a fixed structure. Systematic analyses were carried out of isolated shipping water events generated with the wet dam-break method and simulated with OpenFoam Computational Fluid Dynamics toolbox. The numerical approach was validated and then the shipping water loads were examined. It was found that, as roughness increased, the maximum vertical and horizontal loads showed a delay. As the deck length reduced, the vertical backflow loads tended to increase. These results suggest it may be worthwhile examining the behaviour of shipping water as it propagates over rough surfaces caused by fouling, corrosion, or those with small structural elements distributed on them. Moreover, the effect of deck length is important in understanding the order of magnitude of loads on structures with variable deck lengths, and those which have forward and backflow loading stages.

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A Detailed Description of Flow-Deck Interaction in Consecutive Green Water Events

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4049121 ◽

2020 ◽

Vol 143 (4) ◽

Author(s):

Jassiel V. Hernández-Fontes ◽

Edgar Mendoza ◽

Irving D. Hernández ◽

Rodolfo Silva

Keyword(s):

High Speed ◽

Effective Interaction ◽

Dam Break ◽

Green Water ◽

Hydrodynamic Characteristics ◽

Wave Flume ◽

Series Of Experiments ◽

Run Up ◽

Fixed Structure ◽

Air Cavities

Abstract This paper gives a detailed description of the main hydrodynamic characteristics of different types of green water events occurring on a fixed structure in a series of experiments. High-speed video, at 250 fps, was used to capture the flow details from regular waves produced inside a wave flume. The green water events were classified according to their type and the results of the evaluation from the apparent and effective interaction features. The air cavities in the plunging-dam-break (PDB)-type events were almost spherical for longer waves. PDB with large, elliptical cavities, and hammer-fist (HF)-type events occurred with steeper waves. The highest wave front and bow run-up velocities were found in PDB and HF events, respectively. The size of the cavities in PDB events increases and becomes more elliptical for higher bow run-up velocities. The results of these experiments show that not all events can be treated in the same way as the dam-break (DB)-type events when designing structures or implementing models, as not all interactions with the deck happen when the shipping water crosses the bow edge.

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Capturing Two Consecutive Green Water Events by Convolution

Volume 7B: Ocean Engineering ◽

10.1115/omae2019-96747 ◽

2019 ◽

Cited By ~ 1

Author(s):

Jassiel V. Hernández-Fontes ◽

Rodolfo Silva-Casarín ◽

Edgar Mendoza

Keyword(s):

Time Series ◽

Green Water ◽

Analytical Models ◽

Regular Waves ◽

Convolution Model ◽

Water Elevations ◽

Convolution Approach ◽

Fixed Structure ◽

Hydrodynamic Effects ◽

Selection Of

Abstract Capturing the propagation of green water events on in ships and other marine structures is of importance when studying the hydrodynamic effects on their motion and the structure’s behavior. Analytical models used to predict green water elevations, such as dam-break models, have been considered to represent time series of water elevations of single green water events. This paper presents the use of a convolution approach to represent the time series of water elevations of two consecutive green water events on deck of a fixed structure. The procedure is described considering green water events, generated with regular waves, on a barge-type fixed structure. Its application is compared with results available elsewhere in the literature. With the assumptions related with the selection of input parameters of the convolution model, and considering only the first green water event, the results show that this methodology allows two consecutive green water events to be captured acceptably. It is hoped that this methodology will be useful in further time-domain applications which study the dynamic behavior of structures subjected to green water.

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