1,721,128 research outputs found
Wave-seabed-structure-interaction (WSSI) analysis of suction anchors for a single fish cage
No full textSuction anchors have been commonly used in various floating offshore structures because of their high holding capacity and efficiency in construction. The present study proposes an innovative investigation framework that incorporates hydroelastic behaviours of fish cages captured by the lumped mass method software OrcaFlex into the wave-structure-seabed interaction model (WSSI) developed within the open-source finite-volume method (FVM) numerical toolbox OpenFOAM environment. This integration facilitates a comprehensive analysis encompassing hydrodynamic effects, mooring systems, suction anchor performance, and geotechnical responses. The numerical results indicate that, due to the obstruction effect of the anchor skirt wall, the dynamic response of the seabed soil periodically manifests outside the suction anchor, with a minor concentration observed within the soil near the anchor lid and tips, while the effect of mooring forces is more pronounced in the soil inside the anchor. Parametric studies illustrate that the soil friction resistance of suction anchors with different configurations in the mooring system exhibits varying sensitivities to wave parameters.Full Tex
Seabed liquefaction around breakwater heads at a river mouth: An integrated 3D model
No full textIn this paper, a 3D model is developed to investigate the foundation stability around breakwaters at a river mouth, where both ocean waves and river currents are considered. The present model consists of flow and seabed sub-models. In the flow sub-model, the VARANS equations is used to describe hydrodynamic process, while the dynamic u−p approximation is employed in the seabed sub-model. Based on the integrated model, both oscillatory and residual liquefaction phenomenon is investigated by adopting the poro-elastic and poro-elastoplastic seabed models, respectively. The numerical results reveal that the breakwaters at the river mouth with the river current significantly alter the hydrodynamic properties around breakwater heads. Furthermore, the dynamic soil responses and liquefaction zones predicted by the poro-elastic and poro-elastoplastic seabed models show the completely different development trend, which the latter seabed has more intense and severe reactions. The parametric study indicates that the breakwater foundation is more likely to be liquefied in a loosely deposited soil under larger waves. The river currents can exacerbate the liquefaction condition in the region near breakwater heads. In addition, the pore pressure is smaller in front of a milder slope of breakwater flank and a round breakwater head with a smooth slope.Full Tex
Comparison of existing poroelastic models for wave damping in a porous seabed
No full textMechanism of wave-seabed interaction has been extensively studied by coastal geotechnical engineers in recent years. Numerous poro-elastic models have been proposed to investigate the mechanism of wave propagation on a seabed in the past. The existing poro-elastic models include drained model, consolidation model, Coulomb-damping model, and full dynamic model. However, to date, the difference between the existing models is unclear. In this paper, the fully dynamic poro-elastic model for the wave-seabed interaction will be derived first. Then, the existing models will be reduced from the proposed fully dynamic model. Based on the numerical comparisons, the applicable range of each model is also clarified for the engineering practice
Two-way coupling model for wave-induced oscillatory soil response around marine structures
No full textConsiderable efforts have been devoted to the topic of wave–seabed interactions in the last two decades because of growing offshore activities. The existing studies have based on one-way coupling approach. In this study, a new two-way coupling algorithm is proposed to overcome the contradiction at the fluid–sediment interface between physical process and the existing theoretical models. The numerical results indicates that the seabed responses obtained by the two-way coupling model are slightly lower than that of the one-way coupling model. However, the two-way coupling model significantly affects the Shields number that would further affect the scour process. Parametric analysis indicates that larger wave height, current velocity and soil permeability and smaller water depth, shear modulus and saturation degree would increase the difference of two coupling algorithms. Meanwhile, the difference between two coupling algorithms is significant around the mono-pile and dumbbell cofferdam, compared with the case without a structure.Full Tex
A 3-D Model for Ocean Waves Over a Columb-Damping Poroelastic Seabed
No full textThe evaluation of the wave-induced seabed instability in the vicinity of a breakwater is particularly important for coastal and geotechnical engineers involved in the design of coastal structures. In this paper, an analytical solution for three-dimensional short-crested wave-induced seabed instability in a Coulomb-damping porous seabed is derived. The partial wave reflection and self-weight of breakwater are also considered in the new solution. Based on the analytical solution, we examine (1) the wave-induced soil response at different location; (2) the maximum liquefaction and shear failure depth in coarse and fine sand; (3) the effects of reflection coefficients; and (4) the added stresses due to the self-weight of the breakwater
Wave-Induced Dynamic Seabed Response Around a Submerged Breakwater With Dynamic Permeability
No full textIn this paper, an integrated numerical model with Open-FOAM for the wave-breakwater-seabed interactions problem is presented. Unlike previous studies available in the literature, the present model adopts Biot’s u-p approximation and considers dynamic seabed permeability, which is a function of pore-fluid pressures in the seabed. The proposed model is verified against the existing experimental data. The numerical examples show that dynamic permeability has a significant effect on wave-induced dynamic soil responses, which will cause a deeper and wider liquefaction zone compared with the conventional models with constant permeability. Ignoring the effects of dynamic permeability could significantly impact the transient seabed liquefaction depth and the stability of offshore structures.No Full Tex
PORO-FSSI-FOAM model for seafloor liquefaction around a pipeline under combined random wave and current loading
No full textIn this study, unlike most previous investigations have limited to the regular wave conditions or combined wave and current conditions, a numerical model for seabed response around a pipeline in a trenched layer due to random waves is established. Three different wave spectra including the JONSWAP spectrum, Bretchneider–Mitsuyasu spectrum and Pierson–Moscowitz spectrum are considered in the present model for the simulation of random waves. Numerical examples indicate that the irregular wave-induced pore-water pressure can randomly amplify the upward gradient of the pore-water pressure in the porous seabed, making the backfill sand layer more likely to be liquefied at a deeper depth. It is observed that the upper width of the trench layer becomes larger once the seabed liquefaction occurs, which can effectively prevent the seabed liquefied surface from penetrating into the bottom of the pipeline by increasing the backfill thickness to twice of the pipe diameter. The superimposition of the irregular waves on the following current has more significant effect on the maximum-development of the seabed liquefaction depth, which is particularly obvious when the sand-bed is in the random wave system by using the JONSWAP spectrum.No Full Tex
Numerical study for wave-induced oscillatory seabed response around pile foundations using openFOAM
No full textIn this paper, a three-dimensional numerical model for wave–seabed interactions around a group of pile foundations isproposed. Unlike in previous studies, both wave and seabed submodels are developed based on the open source libraryOpenFOAM (version 4.0, foundation). In this model, the wave motion is governed by RANS equations, while the porous flowin the seabed is governed by dynamic poro-elastic uƒp approximation. The present model is first validated with the previouslaboratory experiments for a single pile. Then, the present model is further applied to the cases of group of pile foundations.Numerical results indicate that the wave characteristics as well as the configurations of the structures can significantly affectthe oscillatory pore water pressures and vertical effective normal stresses around a group of pile foundations.No Full Tex
Two-dimensional one-way coupled modelling for fluid-structure-seabed interactions around a semicircular breakwater using OpenFOAM
No full textSemicircular breakwaters, preferred for their lighter weight, wider base and superior resistance to overturning and sliding, have seen focused research on wave forces and hydrodynamic performance. Despite documented failures due to seabed instability, numerical examinations of the seabed response and stability around these structures are lacking in the literature. This study establishes an OpenFOAM model to numerically investigate hydrodynamic interactions, structural dynamics, seabed consolidation and liquefaction potential near a semicircular breakwater in two-dimensional, addressing complex fluid–structure-seabed interactions in a one-way coupling manner. A novel method for determining the compressibility of the pore fluid has been implemented, which integrates geostatic stress, atmospheric pressure and wave-induced excessive pore pressure within the seabed. The numerical results indicate that seabed responses are sensitive to the bulk modulus of pore air in partially saturated cases, where a decrease in pore pressure, an increase in the vertical effective stress and a decrease in the horizontal effective stress are observed. Further numerical analysis reveals that the most vulnerable part of the breakwater appears on the wave-facing side of the caisson, where reinforcement measurements are recommended during construction. A pronounced liquefaction zone is observed ahead of the breakwater, corresponding to the area with upward seepage, which is attributed to the combined effect of hydrodynamic interactions and direct stress action transferred from the semicircular breakwater.Full Tex
The instantaneous seabed liquefaction around offshore pile-type foundation and seabed protection under combined wave and current loading
No full textThe physical processes involved in the wave–seabed–mono-pile interactions are rather complex, and its upper and lower structures are affected by different loads. This paper presents the application of a three-dimensional numerical model, which was validated with the laboratory experiments available in the literature. First, the soil response induced by the combined wave and current around a mono-pile is discussed, and then the stability of the pile foundation is further evaluated. Numerical examples demonstrate the wave run-up and the distribution of seabed liquefaction around piles are closely related to characteristics of ocean currents. Meanwhile, for the pile group system, the hydrodynamic and dynamic seabed response characteristics are regarded as a function of pile group layout, which will affect the development of the near-trapping phenomenon under the combined wave–current loading. Furthermore, the application of protection mattresses around the pile group is proven to be an effective option for reducing the potential of seabed liquefaction, which is not considered in previous studies.Full Tex
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