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.
This paper presents the first attempt to estimate the numerical uncertainty in wave propagation studies. This work was motivated by a current project at LabOceano (COPPE/UFRJ) related to studying the dynamic behaviour of oil containment booms on waves and currents. To study the dynamics of an oil boom, the influence of the viscous effect needs to be taken into consideration due to the geometry of the boom. Numerically, this can be achieved using software that solves the Navier-Stokes equation. However, prior to evaluating the wave-structure interaction using a viscous model, it is important to evaluate how the numerical model represents the wave flow only, which is the focus of the present paper. Thus, a model based on the continuity and momentum equations available in the software package StarCCM+ is used to simulate the wave propagation. The computational domain is discretized using a trimmer mesh. The results obtained for a regular wave with a wave steepness (H/L) equal to 0.025 are presented. The numerical uncertainties in the mean wave height and in the mean wave period are estimated along the domain using the methodology proposed by [8]. The wave elevation is also compared with the second-order Stokes wave solution.
Circular cylinders are one of the most common geometries used in many structures, such as fixed platforms, risers, umbilical cables, offshore fish farms, floating offshore wind turbines, wave energy devices, plastic cleanup booms, and oil containment booms. Although partially submerged horizontal circular cylinders can be found in many offshore and marine structures, few works have investigated the influence of their positions beneath the free surface and the resulting wave force. The present work aimed to numerically study the wave force acting on a fixed horizontal circular cylinder near the free surface for different depths. The wave flow was modeled using a viscous model available in the StarCCM+ software using a two-dimensional numerical wave tank. The governing equations were solved using the finite volume in an unstructured mesh. A circular cylinder with a diameter (D) of 0.10 m and a regular wave with a steepness (H/L) of 0.025 were used in the present study. In this case, the cylinder diameter is much smaller than the wave length. Three different submerged depths were investigated, and the numerical results were compared with experimental data extracted from Dixon [1]. Good agreement was found for the first two cylinder positions (zc/D = 0 and −0.3). For the last case (zc/D = −0.5), a phase shift was observed. However, by correcting it, the agreement between the numerical and experimental data was also good.
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