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Research Papers: Ocean Engineering

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

[+] Author and Article Information
Jassiel V. Hernández-Fontes

LabOceano/COPPE,
Federal University of Rio de Janeiro,
Rio de Janeiro RJ 21941-907, Brazil
e-mail: jassiel@oceanica.ufrj.br

Marcelo A. Vitola, Monica C. Silva, Paulo de Tarso T. Esperança, Sergio H. Sphaier

LabOceano/COPPE,
Federal University of Rio de Janeiro,
Rio de Janeiro RJ 21941-907, Brazil

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 4, 2017; final manuscript received April 18, 2018; published online May 21, 2018. Assoc. Editor: Ould el Moctar.

J. Offshore Mech. Arct. Eng 140(5), 051101 (May 21, 2018) (10 pages) Paper No: OMAE-17-1100; doi: 10.1115/1.4040050 History: Received July 04, 2017; Revised April 18, 2018

## Abstract

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).

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Topics: Waves , Water , Dams , Probes

## References

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## Figures

Fig. 1

Types of green water events on a fixed structure: (a) DB, (b) PDB, (c) plunging-wave, and (d) HF (Adapted from Greco et al. [10])

Fig. 2

Wet dam-break approach: (a) initial conditions and (b) resultant flow after gate is removed

Fig. 3

Patterns of wet dam-break: resulting waves for different ratios: (a) type 1, (b) type 2, (c) type 3, and (d) type 4 (Adapted from Nakagawa et al. [15])

Fig. 4

Installation used for the experiment: (a) tank and internal structure, (b) gate, and (c) weight

Fig. 5

Schematic views of the experimental setup

Fig. 6

Main dimensions: (a) internal dimensions of the tank and rectangular structure and (b) positions of sensors

Fig. 7

Time evolution of the mean water level (solid line) with standard deviation for case 2: (a) WP1 and (b) WP0

Fig. 8

Water elevations at WP2 and WP3 for case 5

Fig. 9

Parameters for estimating vertical velocities from wave probe data

Fig. 10

h¯em versus h¯wm for all cases

Fig. 11

Patterns found for the different cases. Images were taken 0.12 s after the water level reached the deck level for each case.

Fig. 12

Time evolution of the first pattern (case 2)

Fig. 13

Time evolution of the second pattern (case 5)

Fig. 14

Time evolution of the third pattern (case 6)

## Errata

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