Action Of Regular Waves Research Articles

Numerical modelling of the spatial distribution of wave overtopping water behind dikes under regular wave action using OpenFOAM

The spatial distribution of wave overtopping water behind dikes is a key parameter for assessing the safety zone behind dikes in coastal areas, and it is essential for the safety of pedestrians behind dikes and the placement of critical infrastructure. A 2D OpenFOAM numerical model is validated using experimental data for predicting overtopping discharges and the spatial distribution of wave overtopping water behind a dike. The influences of slope angle, berm, landward ground level, relative structure freeboard, and product of incident wave height and wavelength are studied using a validated numerical model. Numerical model outcomes indicate that the lower slope angle has a critical value that is to be determined by the breaker parameter. Tests were conducted for a range of breaker parameters, including structure freeboard, and empirical-based predictive equations were derived for overtopping events under different wave conditions. We also found that the extent of the hazard area due to wave overtopping is significantly reduced when the landward ground level is negative. The findings of this study provide data and predictive formulas for assessments of the hazard zones behind the dikes and indicate the capability of numerical models in the design and safety assessment of dikes.

Wave Tank Experiments Of A Novel Floating Photovoltaic System

Solar photovoltaic (PV) energy, alongside other renewables, is expected to lead the energy sector. However, large-scale ground-mounted PV generation requires a significant amount of land, prompting conflict with other uses. On these grounds, floating PV (FPV) technology is gaining interest (Rosa-Clot and Tina, 2020). While commercial FPV is already being deployed on freshwater bodies, efforts are being undertaken towards harnessing solar energy on the untapped surface of the ocean (Oliveira-Pinto and Stokkermans, 2020). The main challenge is to develop a cost-effective technology capable of withstanding extreme environmental conditions whilst ensuring platform stability, to minimize misalignment of the solar panels that could result in significant efficiency loss (Claus and López, 2022). Several marine concepts have been proposed, with most of them leaning towards flexible design strategies, similar to those applied in freshwater (Claus and López, 2023). Researchers at the University of Oviedo, Spain, are developing a novel FPV system that is specifically designed for marine conditions, following a rigid design approach (Figure 1). The concept leverages the combination of two distinct elements: a double-axis solar tracker, maximizing solar energy generation, and a tension-leg platform (TLP), ensuring structural performance and stability. This research showcases the wave tank experiments, under regular wave action.

Numerical simulation of the slamming effect of regular waves and freak waves on ultra heavy-lift amphibious connector

The Ultra Heavy-lift Amphibious Connector can be used for sea and land operations. When the amphibious connector opens the bow door, it will inevitably suffer from the combined action of wind, waves, currents, and other factors, resulting in the slamming of the wave on the hatch and various landing ship hull movements in the process. Due to the complexity of the actual UHAC model, in order to save computing resources, this paper selects the external load on the UAHC hatch when it is operated in water when the door is closed. The effects of crest height, draught, and focus position on UHAC slamming under the action of regular waves and freak waves were analyzed. Based on the viscous flow theory, the CFD commercial software FLUENT is used to simulate the interaction between the reduction of regular waves and floating structures. The simulation results are compared with the experimental results to verify the feasibility of the proposed method. Since the published UHAC data cannot be found in the network environment, this paper draws the UHAC based on the only data on the Internet and studies the slamming load of the wave on the UHAC on this basis.

Long-term extreme responses of torsional moments at two-directional hinges for moored very large floating structures

This paper presents an analysis procedure for estimating long-term extreme torsional moments at connections of very large floating structures (VLFS) with two-directional hinges and mooring lines under random waves. This procedure, compared to the common short-term estimation method, can accurately and quickly calculate the extreme response at a certain return period. Applying a coupled frequency-time domain approach, we simulate the hydroelastic response of VLFS with two-directional hinges and vertical mooring lines. In order to validate the proposed approach, numerical simulations are firstly carried out under the action of regular waves. The present approach demonstrates a high level of consistency with experimental data and numerical results from existing studies in terms of vertical displacement, bending moment and shear force. Then, on the basis of the short-term extreme response distribution and environmental model, a procedure for solving long-term extreme responses of the structure is introduced. The long-term extreme response characteristics of the torsional moment at hinges are evaluated and studied in depth using the procedure, providing a reference for the structural design of moored VLFS with two-directional hinges.

On the hydrodynamic behaviour of second-order harmonic induced sloshing-mode resonance in moonpool

Fluid resonance in moonpool formed by two-identical rectangular hulls under the regular-wave action is investigated by employing the Computational Fluid Dynamics (CFD) package OpenFOAM®. In this study, the second-order harmonic induced sloshing-mode resonance occurs simultaneously with the first-order induced piston-mode resonance, generating a significant peak value on the free surface amplitudes in moonpool at the corresponding frequency. One period of piston-mode oscillation and two periods of sloshing-mode oscillation can be identified during one incident wave period. It is confirmed that the piston- and sloshing-mode resonances above are generated by the wave frequency and double frequency of incident waves, respectively. The non-monotonic variations of normalized resonant amplitudes in moonpool with incident wave amplitudes can be observed, which is the combined influence of free surface nonlinearity and energy dissipation on wave responses in moonpool. Finally, the second-order harmonic induced sloshing-mode resonance can also affect horizontal wave forces; while it has insignificant effect on vertical wave forces.

Experimental Study on the Hydrodynamic Characteristics of a Fixed Comb-Type Floating Breakwater

A comb-type floating breakwater is a new wave dissipation structure with particular force and dissipation performance advantages due to the two wave-reflecting surfaces. In this article, physical model experiments are used to study the hydrodynamic characteristics of a fixed floating comb breakwater and two structural optimization-based measures under the combined action of regular waves, irregular waves, and wave currents. The effects of factors such as the relative width, relative wave height, water flow velocity, and irregular waves on the transmission coefficient of the breakwater are analyzed. In addition, the characteristics of the transmission wave waveform are analyzed based on the time and frequency domains. The results show that (1) the wave transmission coefficient of a comb-type floating breakwater is lower than that of a rectangular floating box for long-period waves, while the transmission coefficient is larger than that of a rectangular floating box for short-period waves. (2) Under combined current and waves, the superimposition of bidirectional currents can increase the transmission coefficient, and the transmission coefficient increases with increasing current speed. The superimposition of the anti-directional current can decrease the transmission coefficient. (3) Moreover, with the same wave parameters, the transmission coefficient for irregular waves is larger than that of regular waves. (4) Finally, extending the bottom plate and adding lower baffles can effectively enhance the wave dissipation effect of the comb-type floating breakwater while also stabilizing the transmitted wave waveform.

A numerical study on the wave loading on offshore structures of different cross-sectional geometries under the action of regular waves

Coastal engineering and maritime hydraulics have experienced significant development over the years with the construction of bridges, oil exploration platforms, and ports, highlighting the importance of studying and quantifying the efforts resulting from wave loads on these structures. The present work aims to identify how a variation in the geometry of the cross-section, along the wave climate, can modify the magnitude of the wave loadings experienced by the structure. The open-source computational code OpenFOAM v. 4.1 was applied in the considered cases, along with the OlaFlow extension, considering the application of a structured mesh, the VOF (Volume of Fluid) methodology for representing the free surface, and the turbulence modeling according to Reynolds averaged equations (RANS). The results demonstrated that the shape of the cross-section plays an important role in the efforts experienced by the structure, and this influence is directly related to a characteristic length, whose intensification causes an increase in the magnitude of the experienced horizontal force. Likewise, by defining important dimensionless parameters, it was possible to obtain approximate expressions to determine the maximum wave force on the structures. The results and analyses carried out demonstrated that the force value calculated according to this approximation methodology is quite adequate, presenting relative errors smaller than 11,00%, corresponding to a relevant simplified approach for the determination of the maximum wave loads experienced by the structures, which can be important for proper design and analysis.

A method to calculate the vertical force on a horizontal plate above still water level under the action of waves

A method is investigated to calculate the vertical force on a horizontal plate above still water level under the action of waves in this paper. The wave uplift force is divided into buoyancy force and impact force. Based on the discrete finite element analysis method, the calculation formula of buoyancy force is given and the calculation formula of impact force under the action of regular waves is derived through impulse theory. Then, a formula is proposed to solve the additional mass of liquid impact on the plate. Taking model tests in literature as an example, two different approaches based on the Finite Element Method are presented to verify the calculation method. The comparative analysis shows that the results of the two methods are both consistent with the test results shown in the literature, computation theories of wave uplift force and calculation formula of added mass of impact liquid are verified. On the basis of verifying the calculation theories, the distributions of buoyancy and impact force on the horizontal plate, the time history curves of buoyancy and impact force of the differential element and the relationships between wave uplift forces and wave periods, wave height and plate clearances are discussed.

Effect of cable layout on hydrodynamic response of submerged floating tunnel under wave action

A submerged floating tunnel (SFT) is a new type of traffic-crossing scheme in relatively deep waters that realizes suspension fixation through gravity, buoyancy, and cable force. The cable mainly constrains the SFT, and its layout has a critical impact on the dynamic characteristics of the SFT. In this study, hydrodynamic experiments are conducted on a reduced-scale model of the SFT under regular waves. The acceleration of the SFT tunnel, cable force, wave height, and other data are collected. The dynamic response of the SFT with three cable layouts (parallel, inclined, and mixed) is analyzed. Results show that the dynamic response of the SFT with a parallel cable layout is considerably less than that of the other two cable layouts under the action of regular waves. The amplitude of cable force at the upstream side is generally less than that at the downstream side for the inclined cable of the SFT with inclined and mixed cable layouts. The cable slack phenomenon reduces the overall constraint stiffness of the SFT, and the dynamic response considerably exceeds that under non-slack conditions. Resonance zone and long-period waves are the main excitations causing the motion of SFTs when the submerged depth is at safe level.

Wave forces acting on the coastal bridge deck under focused and regular waves

Coastal bridges in hurricane-prone zones can suffer from forces due to the combined action of storm surges and water waves. The wave loads acting on coastal bridges with box girders are experimentally investigated using focused and regular waves, which induce different wave forces, especially for long waves. Visual observations show that air bubbles and overtopping water influence the wave forces during regular wave action.

Experimental study on hydrodynamic response of a floating rigid fish tank model with slosh suppression blocks

The development of slosh suppression blocks is an important step forward for mitigating sloshing in floating closed containment fish tanks and makes the tanks suitable for operating in a broader range of wave conditions. This experimental study investigates the motion and sloshing response of a scaled floating rigid containment tank model under regular wave action in a wave flume. The tank is fitted with slosh suppression blocks of different dimensions to investigate their effectiveness in mitigating sloshing while considering the state of the internal fluid for fish well-being. This study shows that by sacrificing moderately higher sloshing amplitudes at lower excitation periods, slosh suppression blocks are able to reduce the overall sloshing amplitudes and mitigate the build-up to large sloshing amplitudes. By letting fluid overtop onto the slosh suppression block disturbances to the main fluid volume are minimised, thereby preserving a calm living environment for the fish below. Effective slosh mitigation allows for deploying these closed containment systems in higher energy fish farming sites as the aquaculture industry expands operations into more spacious offshore sites.

Study of the Interaction between Regular Waves and a Wind-Fish Combined Structure

The combination of a wind turbine and fish cage (wind-fish) is able to solve the complex issue of power supply for deep-sea aquaculture. Nevertheless, the hydrodynamic coupling between the fish cage and the wind turbine foundation is increasingly complex, and there is little research on the related hydrodynamics. In this paper, the hydrodynamic research on the wind turbine foundation and fish cage structure is carried out using numerical simulation, in which the porous medium model is adopted to simulate the effects of the fish cage on the flow field. By analyzing the hydrodynamic characteristics of the combined structure of an offshore wind turbine and aquaculture cage under the action of regular waves, the load on both the cage in the combined structure and the wind turbine foundation, and the overall load on the combined structure of offshore wind turbine and cage are obtained. The effects of wave parameters, structural dimensions, cage submergence depth, and biological attachment on cage load, wind turbine foundation load, and overall load of the combined structure are analyzed. The results demonstrate that the wind turbine foundation is persistently the central part of the combined structure. The wave height, water depth, and degree of attachment of marine organisms all have different effects on the amplitude of the structural load. In contrast, the wave period, cage geometry, and cage submergence depth have no significant effects on the amplitude of the structural load. In addition to the water depth, other factors will affect the proportion of the load on the wind turbine foundation and the total load as well.

Effect of Considering Wave Angles on the Motion Response of Oversized Floating Bodies in Offshore Airports under Irregular Wind and Wave Loads

Most existing studies are based on the hydroelastic response of oversized floating bodies under regular waves, ignoring the effect of wave conditions and incident wave angle on the vibration response of oversized floating bodies in real sea conditions. In this paper, the stability performance of a single module of a mega-floating body at an offshore airport was investigated by using STAR-CCM + numerical simulations based on a specific model, with the introduction of parameters under extreme random wind and wave combined sea conditions. By comparing and analyzing the distribution characteristics of the single module floating body under the action of regular waves and irregular waves, wind, and wave load, and by considering the wave angle along the flow direction, as well as the spreading direction and vertical displacement value under the action of mooring, the overall displacement amplitude of rigid displacement, elastic deformation displacement and considering the influence of both, and the distribution law of motion response along the length of the floating body, we summarize the influence of the wave angle on the dynamic response of an oversized floating body of an offshore airport. The results show that the maximum value of the hydro-elastic response tends to appear at the head and tail of the floating body, the rigid body vertical displacement dominates the role, the amplitude of all displacements of the floating body under the action of the cross wave is larger, and the stress area along the floating body is larger when the wave angle is between 15–30°. The floating body stress value is smaller with angles of 30–65°, and the ability to bear the load is stronger. The hydroelastic response under irregular wave conditions is more sensitive to the wave direction angle, and the elastic deformation has less influence.

CFD simulation of floating body motion with mooring dynamics: Coupling MoorDyn with OpenFOAM

It is increasingly popular to use Computational Fluid Dynamics (CFD) models to study floating structures subjected to ocean waves, especially when it comes to applications of floating offshore wind turbines and Wave Energy Converters (WECs). Mooring dynamics are currently lacking in most of these applications. This paper presents a coupled simulation study of moored floating body motion by coupling two open-source libraries: a finite volume CFD toolbox, OpenFOAM, and a lumped-mass mooring model, MoorDyn. The instantaneous floating body position and velocity are passed from the body motion solver in the CFD model to the mooring model to calculate the fairlead kinematics. The mooring reaction forces, which are calculated by MoorDyn after updating the mooring system states, are then returned to the body motion solver to update the floating body motion. Both mesh deformation and overset mesh methods are used as the mesh motion solver in the CFD model to account for the floating body motion. The coupled model was validated against experimental measurements for a floating box moored with four catenary lines under the action of regular waves, which came from a preliminary test campaign for WECs. Apart from the lumped-mass mooring model, the present work also coupled a quasi-static mooring model and a finite element model with the floating body motion solver in OpenFOAM. The mooring line tensions predicted by these models were compared. The coupled model equipped with three mooring line codes may be further used to carry out survivability studies of FOWTs and WECs subject to severe sea states.

Hydrodynamic performance of concave front pile-supported breakwaters integrated with a louver wave screen

Pile supported breakwaters for water depths greater than 20 m are environmentally friendly and are more economical than the rubble mound breakwaters. An experimental investigation is carried out to explore the hydrodynamic performance of two different concave front pile-supported breakwaters integrated with a louver wave screen (LWS) on their seaside. The LWS consists of an array of plates inclined at 60° to the horizontal and mounted one above the other with spacing such that the porosity is 25%. The breakwater models are subjected to the action of regular waves in a wave flume covering intermediate to deep-water conditions. It is found while, the wave transmission past the breakwaters in presence of LWS is not significantly altered, the reflection from the structure significantly reduces, the rate of reduction being higher for the model with a steeper slope. The study also shows a reduction in the wave run-up and induced pressures over the concave profiles in the presence of LWS. The usefulness of wave screens in improving the performance of a breakwater depends on the breakwater profile in addition to the type of the wave screen which is the main finding of the study.

Experimental Investigation of the Response of Monopiles in Silty Seabed to Regular Wave Action

Experimental Investigation of the Response of Monopiles in Silty Seabed to Regular Wave Action

A Boussinesq-Type Model for Nonlinear Wave-Heaving Cylinder Interaction

In the present work, a Boussinesq-type numerical model is developed for the simulation of nonlinear wave-heaving cylinder interaction. The wave model is able to describe the propagation of fully dispersive and weakly nonlinear waves over any finite water depth. The wave-cylinder interaction is taken into account by solving simultaneously an elliptic equation that determines the pressure exerted by the fluid on the floating body. The heave motion for the partially immersed floating cylinder under the action of waves is obtained by solving numerically the body’s equation of motion in the z direction based on Newton’s law. The developed model is applied for the case of a fixed and a free-floating circular cylinder under the action of regular waves, as well as for a free-floating cylinder undergoing a forced motion in heave. Results (heave and surge exciting forces, heave motions, and wave elevation) are compared with those obtained using a frequency domain numerical model, which is based on the boundary integral equation method.

Numerical study on hydrodynamic characteristics of coastal bridge deck under joint action of regular waves and wind

In harsh ocean environment, there are complex interactions between extreme surge waves and strong wind during hurricanes. Coastal infrastructures, such as coastal bridges, ineluctably need to withstand the joint action of waves and wind. During past few decades, many researchers have carried out a lot of theoretical, experimental, and numerical simulation work to study the damage mechanism of coastal bridges during extreme weather events. According to the authors’ knowledges, hydrodynamic characteristics of the coastal bridge deck under the joint action of surge waves and onshore wind have been largely ignored in previous researches. As one of the preliminary attempts, a series of numerical simulations have been performed to systematically investigate the hydrodynamic characteristics of coastal bridge deck under joint action of regular waves and onshore wind by considering the effects of prominent factors, such as wind speed, wave height, submersion depth, and water depth. The results indicates that the existence of the onshore wind can significantly distort the incident wave profile, enhance the intensity of wave impacting bridge deck, and generate the suction effects over the bridge deck, which will finally affect the hydrodynamic characteristics of the coastal bridge deck under the impact of regular waves. It is hoped that findings drawn from this study can further enhance our understanding on damage mechanism of coastal bridge decks during extreme weather events.

Numerical investigation on the wave force characteristics of multi-cylinder with equilateral-triangular arrangement

Based on the open source program DualSPHysics, a numerical investigation is carried out on the hydrodynamic characteristics of multi-cylinder with equilateral-triangular arrangement and the wave field distribution characteristics under the action of regular waves. With the SPH method, the hydrodynamic response characteristics of multi-cylinder with equilateral-triangular arrangement are analyzed under different wave directions. The phase difference distribution characteristics of the wave force on multi-cylinder with equilateral-triangular arrangement are analyzed, as well as the wave field distribution characteristics under different wave angles. In addition, the wave force distribution characteristics and the phase difference distribution characteristics of multi-cylinder with equilateral-triangular arrangement are explored under different wave parameters (wave period and wave height). Through the observations of the hydrodynamic forces induced by the wave, the phase difference of these forces on upstream cylinder and downstream cylinder is the largest when the wave angle is 30°. The maximum wave force of the cylinder is roughly proportional to the distance between the center of the cylinder and the x-axis centerline of the wave field.

The influence of incident angles and length-diameter ratios on the round-ended cylinder under regular wave action

The round-ended cylinder is commonly applied in coastal engineering as foundation. While researches related to the round-ended cylinder are pretty limited. In the present study, the influence of the incident wave angles and length-diameter (LD) ratios is investigated through numerical simulation. An equation is then proposed to calculate the maximum horizontal wave force based on numerical solutions and verified by random cases. Additionally, results of numerical simulation, proposed equation, the Chinese design code and the American design code are compared with each other. The results show that the proposed equation has good accuracy and the product of a safety factor, in the range of 1.5–2.0, with the proposed equation result is recommended in practical engineering. Besides, small LD ratios are suggested to be adopted in the structure design.