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The selection of wave force models will significantly impact the structural responses of floating wind turbines. In this study, comparisons of wave force model effects on the structural responses and fatigue loads of a semi-submersible floating wind turbine (SFWT) were conducted. Simulations were performed by employing the Morison equation (ME) with linear or second-order wave kinematics and potential flow theory (PFT) with first- or second-order wave forces. A comparison of regular waves, irregular waves, and coupled wind/waves analyses with the experimental data showed that many of the simulation results and experimental data are relatively consistent. However, notable discrepancies are found in the response amplitude operators for platform heave, tower base bending moment, and tension in mooring lines. PFT models give more satisfactory results of heave but more significant discrepancies in tower base bending moment than the ME models. In irregular wave analyses, low-frequency resonances were captured by PFT models with second-order difference-frequency terms, and high-frequency resonances were captured by the ME models or PFT models with second-order sum-frequency terms. These force models capture the response frequencies but do not reasonably predict the response amplitudes. The coupled wind/waves analyses showed more satisfactory results than the wave-only analyses. However, an important detail to note is that this satisfactory result is based on the overprediction of wind-induced responses.

This study analyzes the hydrodynamic performance of an H-shaped pile-restrained composite breakwater integrated with a pair of horizontal plates placed on the seaside and the leeside of the breakwater. The wave interaction with the H-shaped breakwater is examined by analyzing the wave reflection, transmission, and dissipation coefficients. Additionally, the horizontal wave force coefficients are evaluated to analyze the effectiveness of the horizontal plates when integrated with the main structure. The primary structural parameters directly affect the performance of the composite breakwater and are varied within the feasible range of nondimensional wave numbers, relative spacings, and incident wave angles. This study presents a comparative analysis of the arrangement of the horizontal plates in terms of spacing and inclinations inward and outward to the breakwater using a multidomain boundary element method (BEM). The variation of the structural parameters proposes suitable dimensions for integrated H-shaped breakwater with horizontal plates that provide optimal performance in shallow and deep-water regions. The optimum plate porosity, dimensions of the H-shaped structure, inclinations, and spacing between the plate and breakwater are thoroughly discussed. This study shows that impermeable plates are the excellent means to control the wave force in the intermediate water depth regions than in deep-water regions at resisting wave force. The wave force coefficient on the breakwater is significantly larger than that on the seaside plates. Interestingly, inward-inclined plates perform most efficiently at angles greater than 5°, except in deep-water regions where horizontal plates perform better. In addition, this study noted that regardless of water depth, the outward-inclined plates are the least effective in reflecting the incident wave energy. This study will help plan the layout of suitable composite structures for efficient near-shore and offshore harbor protection according to the site criteria and environmental conditions.

The wave-induced motions, and steady wave forces and moments for the oil tanker KVLCC2 in regular head and oblique waves are numerically predicted by using the expanded RANS solver based on OpenFOAM. New modules of wave boundary condition are programed into OpenFOAM for this purpose. In the present consideration, the steady wave forces and moments include not only the contribution of hydrodynamic effects but also the contribution of the inertial effects due to wave-induced ship motions. The computed results show that the contribution of the inertial effects due to heave and pitch in head waves is non-negligible when wave-induced motions are of large amplitude, for example, in long waves. The influence of wave amplitude on added resistance in head waves is also analyzed. The dimensionless added resistance becomes smaller with the increasing wave amplitude, indicating that added resistance is not proportional to the square of wave amplitude. However, wave amplitude seems not to affect the heave and pitch RAOs significantly. The steady wave surge force, sway force and yaw moment for the KVLCC2 with zero speed in oblique waves are computed as well. The present RANS results are compared with available experimental data, and very good agreements are found between them.

The interaction of solitary waves with multiple, in-line vertical cylinders is investigated. The fixed cylinders are of constant circular cross section and extend from the seafloor to the free surface. In general, there are N of them lined in a row parallel to the incoming wave direction. Both the nonlinear, generalized Boussinesq and the Green–Naghdi shallow-water wave equations are used. A boundary-fitted curvilinear coordinate system is employed to facilitate the use of the finite-difference method on curved boundaries. The governing equations and boundary conditions are transformed from the physical plane onto the computational plane. These equations are then solved in time on the computational plane that contains a uniform grid and by use of the successive over-relaxation method and a second-order finite-difference method to determine the horizontal force and overturning moment on the cylinders. Resulting solitary wave forces from the nonlinear Green–Naghdi and the Boussinesq equations are presented, and the forces are compared with the experimental data when available.

A two-dimensional viscous numerical wave tank coded mass source function in a computational fluid dynamics (CFD) software Flow-3D 11.2 is built and validated. The effect of the core influencing factors (draft, breakwater width, wave period, and wave height) on the hydrodynamic performance of a fixed box-type free surface breakwater (abbreviated to F-BW in the following texts) are highlighted in the intermediate waters. The results show that four influence factors, except wave period, impede wave transmission; the draft and breakwater width boost wave reflection, and the wave period and wave height are opposite; the draft impedes wave energy dissipation, and the wave height is opposite; the draft and wave height boost the horizontal extreme wave force; four influence factors, except the draft, boost the vertical extreme wave force. Finally, new formulas are provided to determine the transmission, reflection, and dissipation coefficients and extreme wave forces of the F-BW by applying multiple linear regression. The new formulas are verified by comparing with existing literature observation datasets. The results show that it is in good agreement with previous datasets.

The impact of wave-induced forces on the integrity of stationary oscillating water column (OWC) devices is essential for ensuring their structural safety. In our study, we built a three-dimensional numerical model of an OWC device using the computational fluid dynamics (CFDs) software OpenFOAM-v1912. Subsequently, the hydrodynamic performance of the numerical model is comprehensively validated. Finally, the hydrodynamic performance data are analyzed in detail to obtain meaningful conclusions. Results indicate that the horizontal wave force applied to the OWC device is approximately 6.6 to 7.9 times greater than the vertical wave force, whereas the lateral wave force is relatively small. Both the horizontal and vertical wave forces decrease as the relative water depth increases under a constant wave period and height. In addition, the highest dynamic water pressure is observed at the interface between the water surface and device, both within and outside the front wall of the gas chamber. The dynamic water pressure at different locations on the front chamber increases and subsequently decreases as the wave frequency increases.

Earthquakes in coastal areas frequently trigger tsunami waves, posing significant threats to low-lying coastal bridges. Investigating extreme wave force on bridge deck is crucial for understanding bridge damage mechanisms. However, the majority of current research focuses on single bridge deck, with limited analysis of wave impacts on twin bridge decks. In this paper, solitary wave is utilized to simulate tsunami wave, and a two-dimensional (2D) computational fluid dynamics (CFDs) model to analyze wave–bridge interactions and investigate the impact of tsunami wave on adjacent twin box-girder bridge decks. The numerical model was validated by solitary wave theory and wave force data obtained from the published experiment. Based on this model, the effects of the submergence coefficient, wave height, and deck spacing on the horizontal and vertical forces on the twin box-girder bridge decks were analyzed and compared with those in a single box-girder bridge deck. The results indicate that, firstly, due to wave reflection and the trapped water, the vertical wave force on the twin forward bridge deck significantly surpasses that on the single bridge deck. Furthermore, the twin backward bridge deck experiences greater horizontal force than single deck when the deck is completely submerged. Secondly, the maximum wave force on the twin bridge decks does not always consistently decrease with increasing deck spacing. Finally, the negative horizontal force would exceed the positive horizontal force on the twin forward bridge deck under higher wave. This paper delineates the disparities between twin and single box-girder bridge deck responses to wave action and analyzes the influencing factors. Such insights are pivotal for coastal bridge construction and natural disaster risk assessment.

This paper provides a semi analytical technique to handle the problem of water wave scattering by thin vertical double porous barriers over rectangular trench assuming linear theory. The motivational theme behind this study is the exploration of a novel representation of a breakwater model in the history of water wave theory. Specifically, the study focuses on the wave scattering problem of a pair of thin porous barriers, along with a rectangular trench, incorporating integral equations that encompass both types (half and one-third) of singularities. The problem is put together in terms of integral equations by presuming symmetric and anti-symmetric parts of velocity potential. Using multi-term Galerkin method in terms of Chebychev polynomial and ultra-spherical Gegenbauer polynomial as its basis function due to the edge conditions at the submerged end of the barrier and at the corner of the trench, respectively, to figure out the analytical solutions. The approach of this study also provides a technique for solving a system of integral equations that accommodates various singularities at the corners of the trench (cube root singularities) and submerged edges of the thin porous barriers (square root singularities). The reflection and transmission coefficients, dissipation of wave energy and dynamic wave force are obtained for different parametric values which are depicted graphically against the wave number. It is reliable that the length and position of porous barrier execute a major impact in the reflection and transmission coefficients of surface wave.

Large quasi-elliptical cylinders are extensively used in ocean engineering. To enhance a better understanding of the hydrodynamic wave force on such quasi-elliptical cylinders during extreme events, a series of experiments on extreme wave interaction with a quasi-elliptical cylinder were conducted. A series of waves with various wave heights, wave periods, and wave incident directions were tested to investigate the wave parameter effect and wave directionality effect on the wave forces on the quasi-elliptical structure. The experimental results indicate that the extreme wave-induced forces on the quasi-elliptical cylinder are strongly correlated to the wave period and wave incident direction. The peak forces on the quasi-elliptical model do not vary monotonically with the increasing wave period but show an increase followed by a decrease. Both the longitudinal and transversal forces are significantly increased when the wave incident direction changes from 0° to 45° and the wave directionality effect is enhanced when the wave period is decreased. Additionally, the inertial force equation was applied to the wave force estimation for such quasi-elliptical cylinders, and the inertia coefficient CM was fitted based on the experimental results of α = 0°.

The wave interaction with stratified porous structure combined with a surface-piercing porous block in a stepped seabed is analysed based on the small amplitude wave theory. The study is performed to analyse the effectiveness of partial porous structure in increasing the wave attenuation in the nearshore regions consisting of stratified porous structures of different configurations using the eigenfunction expansion method and orthogonal mode-coupling relation. The hydrodynamic characteristics such as wave reflection coefficient, transmission coefficient, dissipation coefficient, wave force impact and surface elevation are investigated due to the presence of both horizontally and vertically stratified porous structures. The effect of varying porosity, structural width, angle of incidence, wavelength and length between the porous block and stratified structure is examined. The numerical results are validated with the results available in the literature. The present study illustrates that the presence of the stratified structure decreases wave transmission and efficient wave attenuation can also be easily achieved. The wave force acting on stratified structure can be decreased if the structure is combined with wider surface-piercing porous blocks. Further, the presence of stratified porous structure combined with porous block helps in creating a tranquil zone in the leeside of the structure. The combination of vertical and horizontal stratified porous structure with surface-piercing porous block is intended to be an effective solution for the protection of coastal facilities.