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In this study, the sediment transport two-phase flow model named SedFOAM is expanded to include soil cohesion, creating a new model named SedCohFOAM within OpenFOAM. The local scouring flume experiment involving a pile on silty seabed and sandy seabed is conducted in a curved flume. Due to the influence of cohesion, the scouring depth at different locations on sandy seabed is 15%–18% greater than that on silty seabed. Observations from this experiment informed the analysis of force balance, wherein the agglomerated silt particles are modeled as large singular entities and the cohesive force is treated as a downward influence that keeps the aggregated particles stationary. Meanwhile, the experimental outcomes are utilized to validate the accuracy of the SedCohFOAM model. The numerical findings demonstrated that SedCohFOAM can simulate the flow field distribution around the pile, variations in seabed shear stress, and alterations in seabed surface morphology. Compared with the SedFOAM model, the SedCohFOAM model has a significantly reduced simulation error in simulating scour on silty seabed. When comparing the cross-sectional profiles of the scour holes derived from the flume experiments with those simulated by SedCohFOAM, it was observed that the ultimate-equilibrium scour depth predicted by the model is consistently lower, but the scour radius in the numerical simulations is larger. The deviation from the experimental results is nearly within 8%, while when the flow velocity is high, the simulation error of the simulated scouring depth behind the pile and the scouring radius in front of pile is amplified. [ABSTRACT FROM AUTHOR]

Duan, L.; Xing, L.; Wang, D.; Fan, M., and Wang, P., 2021. Numerical investigation of wave-induced uplift force exerted onto a shallowly buried pipeline using a two-dimensional fully coupled model for wave-seabed-structure interaction. Journal of Coastal Research, 37(4), 800–812. Coconut Creek (Florida), ISSN 0749-0208. In this paper, a novel two-dimensional numerical model for wave-seabed-pipeline interaction is proposed to investigate the wave-induced uplift force exerted onto a shallowly buried pipeline. Unlike previous models, the present model is fully coupled, and the effects of fluid shear stress at the seabed surface on the soil dynamic response are considered. In this study, the Reynolds-averaged Navier-Stokes equation was applied to simulate flow motions, and the level set method was used to track the free water surface. Meanwhile, Biot's poroelastic equation (u-p mode) was taken to govern the wave-induced oscillatory response of the seabed, and the pipeline was treated as elastic. After validation using data from laboratory experiments in the literature, the novel model was first employed to investigate the distribution of the wave-induced transient seabed response around the shallowly buried pipeline. Then, the effects of the wave parameters, the soil properties, and the pipeline diameter and burial depth on the wave-induced maximum uplift force exerted onto the structure were systematically examined in detail. Finally, wave-induced maximum uplift of the shallowly buried pipeline was predicted based on the numerical results, which may provide some references for engineering practice. Numerical results confirmed that both the nonlinear pipeline-seabed contacts and the fluid shear stress at the seabed surface can greatly affect the soil dynamic response, which should be considered in determining the wave-induced uplift force exerted onto a shallowly buried pipeline. [ABSTRACT FROM AUTHOR]

In this study, the PORO-FSSI-FOAM model is applied to investigate the wave-induced oscillatory soil response during the caisson installation, where the Reynolds averaged Navier-stokes equation is used to simulate the flow motions, and the poro-elastic equation is used to govern the soil dynamic response around the caisson. Unlike previous studies, the caisson installation process is considered when investigating the wave-induced oscillatory soil response in this paper. Firstly, the accuracy of the PORO-FSSI-FOAM model in simulating the wave-seabed interaction is validated. Then, the effects of the submerged depth, the geometrical dimensions and the installation sequence of the caisson on the wave-induced oscillatory pore pressure response are examined, and the momentary soil liquefaction during the caisson installation is explored. Finally, a simple formula that describes the relationship between the maximum soil liquefaction depth and the caisson submerged depth is proposed. Numerical results indicate that the caisson dimensions can greatly influence the wave-induced pore pressure response, and the relationship between the oscillatory pore pressure response and the caisson submerged depth is inconsistent at different locations surrounding the structure. Moreover, the installation sequence can significantly affect the momentary soil liquefaction and the simple formula proposed in this study can provide reference for engineers to assess the seabed stability during the caisson installation. • A three-dimensional numerical model for wave-seabed-caisson interaction was established based on OpenFOAM. • The wave-induced oscillatory pore pressure response during the caisson installation was studied. • The momentary soil liquefaction during the caisson installation was investigated. • A simple method that describes the variation of the maximum soil liquefaction with the submerged depth for different caisson dimensions was proposed. [ABSTRACT FROM AUTHOR]

Duan, L.; Jeng, D.-S.; Wang, S., and Zhu, B., 2019. Numerical investigation of the wave/current–induced responses of transient soil around a square mono-pile foundation. Journal of Coastal Research, 35(3), 625–636. Coconut Creek (Florida), ISSN 0749-0208. A mono-pile foundation is a commonly used supporting base for marine infrastructure in shallow water, such as offshore wind turbine foundations and cross-sea bridges and platforms. Sea floor instability around a pile foundation has attracted much attention among offshore geotechnical engineers. In this paper, a three-dimensional numerical model for wave–seabed–structure interactions is proposed using open field operation and manipulation (OpenFOAM). Unlike previous studies, currents are included in the proposed model and applied to a square cross-section mono-pile foundation. In the model, the flow motion is described by the Reynolds-averaged Navier–Stokes (RANS) equation and k–ϵ turbulence model, and the water free surface is tracked using the volume of fluid (VOF) method. Meanwhile, the soil response is determined by the Biot's poro-elastic equation (u–p approximation), in which the accelerations of the soil displacements are included. After the model is validated with the previous laboratory experiments, it is further used to investigate the transient soil response around the square mono-pile foundation. Numerical results demonstrate that the cross-section shape has significant influence on the distribution of wave/current–induced transient pore pressure but little influence on the maximum soil liquefaction depth. On the other hand, both the current velocity and the seabed permeability can greatly affect the maximum soil liquefaction depth and slightly affect the distribution of pore pressure. Furthermore, the cross-section dimension significantly affects both the maximum soil liquefaction depth and the distribution of the pore pressure around a mono-pile foundation. [ABSTRACT FROM AUTHOR]

The dumbbell-shaped cofferdam has a large-scale and complex geometric shape, which may result in a complicated fluid-structure-seabed coupling mechanism and sophisticated seabed response around the structure. To investigate the wave-induced oscillatory seabed response around a dumbbell-shaped cofferdam, this study simulates the wave-cofferdam-seabed interaction process using a numerical model within the OpenFOAM framework. In this study, the finite volume method is applied to both the wave model and seabed model, thus ensuring the computational accuracy of this study. Biot's poro-elastic theory (u-p approximation) is considered as the governing equation for the dynamic response of the porous seabed, and the fluid motions are simulated based on the Reynolds-averaged Navier–Stokes equation. First, the accuracy of the numerical model for simulating wave-induced soil response is validated against existing experiments. Next, the effects of the submerged depth, wave incidence angle, and wave height on the oscillatory pore pressure response are studied in detail. Finally, momentary liquefaction around the dumbbell-shaped cofferdam is examined. The numerical results indicate that the wave-induced oscillatory seabed response around the cofferdam is considerably affected by the wave height but less affected by the wave incident angle. Moreover, the distribution of the wave-induced pore pressure in the vicinity of the dumbbell-shaped cofferdam is complex, and the maximum liquefaction depth around the cofferdam occurs near the steel casing along the centerline of the cofferdam. [ABSTRACT FROM AUTHOR]

To obtain a better understanding of the oscillatory soil liquefaction around an offshore pipeline, a three-dimensional integrated model for the wave–seabed–pipeline interaction (WSPI) is proposed by combining the Reynolds-Averaged Navier–Stokes equations for flow simulations and the dynamic Biot’s equation (“ u - p ” approximation) for the poro-elastic seabed model. Compared with previous investigations, the wave–current interaction is included in the present WSPI system. At a given time step, the wave pressure extracted from the flow model is applied on the seabed surface to determine the corresponding oscillatory seabed response around an offshore pipeline. The integrated numerical model is first validated using previous laboratory experiments. Then, a parametric study is conducted to examine the effects of flow obliquity and pipeline burial depth on the soil response around an offshore pipeline. Numerical results indicate that the soil under the pipeline is more susceptible to liquefaction at a reduced flow obliquity and pipeline burial depth. Moreover, the liquefaction depth in the case where the wave travels along the current can increase by 10%–30% compared to that in the case where the wave travels against the current, when the magnitude of the current velocity is 1 m/s. [ABSTRACT FROM AUTHOR]

This paper proposes a two-dimensional (2D) coupled model for wave and current-seabed-pipeline interactions to examine oscillatory non-cohesive soil liquefaction around a partially buried pipeline in a trench. Unlike previous studies, two new features are included in this model: (1) wave-current interactions around the pipeline; and (2) fully coupled processes for the wave and current-seabed-pipeline system. In this study, the Reynolds Averaged Navier-Stokes (RANS) equations are applied to simulate the flow field around the pipeline, and Biot's poro-elastic theory for porous media is imposed to govern the soil response due to the wave-current loading. After being validated using data available in the literature, the 2D model is used to investigate the effects of the current velocity, the soil properties, and the wave characteristics on oscillatory non-cohesive soil liquefaction. Using the model, a function for the critical backfill thickness and the wave steepness under various flow and soil conditions is proposed to facilitate engineering practice. [ABSTRACT FROM AUTHOR]

• A novel 3D numerical model for residual seabed response has been developed by redefining the source term of the governing equation. • The wave-current interactions are considered while studying residual soil response near a single pile. • Both the oscillatory pore pressure and the residual pore pressure are considered while determining soil liquefaction potential. The evaluation of seafloor stability is of vital importance for engineers involved in the protection of marine foundations. Hence, it has attracted considerable attention in the field of offshore geotechnical engineering. In this investigation, a novel three-dimensional (3D) numerical model of fluid–seabed-structure interactions (FSSI) is proposed within the framework of OpenFOAM to explore the residual soil dynamic response around a single pile. Different from previous studies, three new features are added in the present model. (i) The wave–current interactions are taken into consideration, (ii) the source term of pore pressure generations is redefined, and (iii) both the oscillatory pore pressure and residual pore pressure are considered while judging the soil liquefaction potential. After verified by previous laboratory experiments available in literature, the novel model is applied to investigate the residual soil response around the single pile induced by natural loadings. The numerical results confirm that the novel 3D model can provide sufficiently accurate predictions of fluid–seabed-structure interactions. Moreover, wave/current characteristics, soil properties, and pile diameter can significantly affect the fluid-induced residual pore pressures along the vicinity of the single pile. [ABSTRACT FROM AUTHOR]

Background: Irrigation is considered to be a critical part of root canal treatment. However, little is known about the effect of needle movement on the irrigation process. Therefore, this study aimed to investigate the influence of the syringe and needle movement on root canal irrigation using a three-dimensional computational fluid dynamics (CFD) numerical model.Methods: The CFD codes Flow-3D was adopted to simulate the root canal irrigation process with the syringe and needle moving up and down in motions at different amplitudes and frequencies. One stationary needle was adopted to allow comparison with the needles in up-and-down motions. Six cases where the needles were moving up and down with different amplitudes and frequencies were used to investigate the relationships between the motion of needle and irrigation efficacy.Results: The stationary needle gained relatively higher flow velocity and apical pressure all through the irrigation process, while the needles in constant up-and-down motions exhibited lower mean flow velocity and apical pressure. The larger the amplitude, the less mean flow velocity and apical pressure were developed. In addition, the needles moving with different frequencies were similar in the terms of irrigant replacement and apical pressure.Conclusions: To avoid periapical extrusion accidents while obtaining adequate irrigant replacement, the needle should be moving up and down with a moderate amplitude during manual root canal irrigation; and the motion frequency was not highly relevant in terms of the irrigation efficiency. [ABSTRACT FROM AUTHOR]

Chen, L.; Zhai, H.; Wang, P.; Zhang, Q.; Wang, S.; Duan, L., and Jeng, D.-S., 2022. Experimental study on irregular wave (current)-induced pore-water pressures around a monopile. Journal of Coastal Research, 38(1), 114–132. Coconut Creek (Florida), ISSN 0749-0208. In this study, a series of flume tests was systematically conducted to study the pore-water pressures around a monopile under wave and current loading, as well as the hydrodynamic response. Unlike in previous studies, the combined irregular wave and current action were studied, and a partially embedded monopile was considered. Moreover, the influence of wave spectra on the pore-water pressures was studied. The following results were obtained. (1) The irregular wave (current)-induced hydrodynamic response and seabed response around the monopile are stronger than those induced by the representative regular wave (current) loading. (2) A larger irregular wave energy can more often cause a larger pore-water pressure. The influence of irregular wave parameters on the pore-water pressures is mainly concentrated in the upper seabed, and the influence range is enhanced for the existence of current. (3) The current greatly influences the pore-water pressures in the upper and middle layers of the seabed; however, in the lower seabed below the monopile, it has a weaker but more complicated effect on the pore-water pressures. (4) Wave spectra have remarkable effects on the pore-water pressures, and the influence range deepens for the action of current on the wave field. [ABSTRACT FROM AUTHOR]

Hurricane-induced wave forces on a box girder deck for a coastal bridge are investigated by experimental tests and numerical simulations. A series of 70 experiments, which include six types of wave heights, three types of deck elevations, and various water depths, are conducted. The results show that there are five types of submergence coefficients that cover the elevated and submerged conditions for each deck elevation. Following the experiments, a two-dimensional numerical model is utilized to investigate the wave forces on the box girder deck, in which Reynolds-averaged Navier-Stokes equations combined with k-ω turbulence model are applied for wave simulations; the volume of fluid method is used to trace the interface of air and water. This numerical model shows a close agreement with the experimental data in most cases. The laboratory experiment and numerical simulation are different compared to other wave-in-bridge studies in that the box girder superstructure is complex and unique. This study can provide a beneficial tool for estimating hurricane-induced extreme wave forces for this type of coastal bridge superstructure. Regular wave forces on a box girder deck are discussed in Part I of these series of works, while the irregular wave forces will be presented in Part II. [ABSTRACT FROM AUTHOR]

• An integrated FEM model of wave-seabed interaction is used to investigate the effects of wave-current action on the slope instability for the foundation trench of immersed tunnel. • The wave and current induced seepage pressure in the seabed is determined by Darcy's law and considered as external load. • The consolidation status of foundation trench after excavation is obtained and set as an initial condition. • The factor of stability (FOS) for the slope depends on the relative distance between the wave crest and slope. • The minimum of FOS corresponding to the most dangerous situation is regarded as the stability index for the slope in the whole process of dynamic wave-current loading. The determination of stability for the submarine artificial slope is important in the construction of offshore structures such as immersed tunnels and embedded pipelines. Aimed at this issue, a two-dimensional (2D) integrated model is proposed to investigate the slope stability of the foundation trench for the immersed tunnel under the combined wave and current loading, as in the real marine environment. The Reynolds-Averaged Navier-Stokes (RANS) equations are solved to simulate the wave field, meanwhile the current is realized by setting boundary inlet and outlet velocity at both sides. The interface between water and air is tracked by conservative Level Set Method (LSM). The wave-current induced pore pressure in seabed is calculated by Darcy's law, and the shear strength reduction method is adopted to judge the damage of the elastic-plastic seabed slope which is described through Mohr-Coulomb constitutive model. The wave-current model is validated through comparing with experimental data and analytical solution. The consolidation status of foundation trench after excavation is obtained and set as the initial condition for analysis. The factor of stability (FOS) for the slope is demonstrated to depend on the relative distance between wave crest and slope. The minimum of FOS corresponding to the most dangerous situation is regarded as the stability index for the slope with specific slope ratio in the whole process of dynamic wave-current loading. Through the parametric analysis based on this new evaluation method, the effects of soil strength parameters, slope ratio and current direction on the slope stability are discussed in detail. [ABSTRACT FROM AUTHOR]

Wang, C.; Jiang, Z.; Wang, D.; Feng, D., and Duan, L., 2020. Effects of the porous medium seabed on the wave load acting on the single pile. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 192–197. Coconut Creek (Florida), ISSN 0749-0208. The characteristics of the seabed greatly affect the interaction between waves and the single-pile foundation structure. It is normal to simplify the porous medium seabed into a rigid, impermeable solid seabed, which ignores the effect of the porous medium seabed on wave energy. This study investigated the effects of the seabed characteristics of porous media on the wave load of the single pile based on the wave-flume test and the three-dimensional numerical model. Five seabed wave-flume tests and the common ocean conditions wave-soil-structure interaction numerical analysis model were designed to verify the accuracy of the numerical model and to analyze the effect of porous media seabed characteristics on wave loads. Results show that the wave load on the single pile depends on the seabed porosity, the average seabed-particle diameter, and the seabed thickness. The seabed-particle diameter has the most significant influence on the wave load of the single pile. The formula for the relationship between the wave load of the single pile and the seabed-particle diameter is derived under different wave conditions. [ABSTRACT FROM AUTHOR]

In this paper, a series of experimental data for wave (current)-induced pore-water pressure around a partially embedded monopile is presented. Unlike the previous studies, the combined action of waves and currents is studied. The partially embedded monopile is considered. The variations of pore-water pressures around the monopile in time and space are investigated by wave flume experiments. The experimental results indicate that the hydrodynamic response and the seabed response caused by the combined action of waves and currents are significantly different from those caused by wave load. When the following current is superimposed on the wave, the wave profile on the lateral side, rather than on the front, of the monopile fluctuates first, and the wave trough of the incident wave becomes small and gentle. Moreover, it was found that the amplitudes of pore-water pressures increase, while the attenuation of pore-water pressures slows down under the large wave energy with a large current. It was further found that the existence of a current has a significant effect on the pore-water pressure at z ∕ h = -0.3 on the front side and on the pore-water pressure at z ∕ h = -0.15 on the back side of the monopile. Additionally, the influence of the current on the vertical and horizontal distributions of pore-water pressures is related to the wave height. • Comprehensive experimental data for pore-water pressure induced by the combined action of regular waves and current around a partially embedded monopile. • Examine effect of wave characteristics and current velocity on hydrodynamic response near partially embedded monopile. • Investigate effect of wave characteristics and current velocity on the variation of oscillatory pore-water pressures. [ABSTRACT FROM AUTHOR]

• Experimental study for random wave-induced soil response around a mono-pile. • The influence of wave height on the maximum pore-water pressure is significant in the region near seabed surface (| z | < 0.3 m). • Significant difference of pore pressure distribution around a mono-pile between regular wave and irregular wave loading. In this study, a series of physical model tests were carried out in a wave flume to study the pore pressures around a mono-pile under irregular waves. The mono-pile was installed to the position of 0.6 m below the seabed surface. The main purpose of this study is to analyze the distribution of pore-water pressure around and beneath the mono-pile under irregular waves. Five different wave spectra were used in the tests. The experimental results conclude that: (1) the pore-water pressure around the pile increases as the increase of significant wave height and period; (2) the maximum pore-water pressure decreases as the increase of seabed depth (z), this trend is significant near the seabed surface (z ≥ −0.3 m), and the influence is not obvious for the region below 0.3 m; (3) at the depth of 0.15 m below the seabed surface (z = −0.15 m), the maximum pore pressure occurs in front of the pile, and at the depth of 0.1 m below the bottom of the pile (z = −0.7 m), the maximum pore-water pressure occurs behind it; (4) the irregular wave-induced seabed response is larger than that of the representative regular wave; and (5) the irregular waves with Pierson–Moscowitz (P − M) spectrum introduce the most significant seabed response among various wave spectra. [ABSTRACT FROM AUTHOR]