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We examine the implementation of a wave-breaking mechanism into a nonlinear potential flow solver. The success of the mechanism will be studied by implementing it into the numerical model HOS-NWT, which is a computationally efficient, open source code that solves for the free surface in a numerical wave tank using the high-order spectral (HOS) method. Once the breaking mechanism is validated, it can be implemented into other nonlinear potential flow models. To solve for wave-breaking, first a wave-breaking onset parameter is identified, and then a method for computing wave-breaking associated energy loss is determined. Wave-breaking onset is calculated using a breaking criteria introduced by Barthelemy et al. (J Fluid Mech https://arxiv.org/pdf/1508.06002.pdf, submitted) and validated with the experiments of Saket et al. (J Fluid Mech 811:642–658, 2017). Wave-breaking energy dissipation is calculated by adding a viscous diffusion term computed using an eddy viscosity parameter introduced by Tian et al. (Phys Fluids 20(6): 066,604, 2008, Phys Fluids 24(3), 2012), which is estimated based on the pre-breaking wave geometry. A set of two-dimensional experiments is conducted to validate the implemented wave breaking mechanism at a large scale. Breaking waves are generated by using traditional methods of evolution of focused waves and modulational instability, as well as irregular breaking waves with a range of primary frequencies, providing a wide range of breaking conditions to validate the solver. Furthermore, adjustments are made to the method of application and coefficient of the viscous diffusion term with negligible difference, supporting the robustness of the eddy viscosity parameter. The model is able to accurately predict surface elevation and corresponding frequency/amplitude spectrum, as well as energy dissipation when compared with the experimental measurements. This suggests the model is capable of calculating wave-breaking onset and energy dissipation successfully for a wide range of breaking conditions. The model is also able to successfully calculate the transfer of energy between frequencies due to wave focusing and wave breaking. This study is limited to unidirectional waves but provides a valuable basis for future application of the wave-breaking model to a multidirectional wave field. By including parameters for removing energy due to wave-breaking into a nonlinear potential flow solver, the risk of developing numerical instabilities due to an overturning wave is decreased, thereby increasing the application range of the model, including calculating more extreme sea states. A computationally efficient and accurate model for the generation of a nonlinear random wave field is useful for predicting the dynamic response of offshore vessels and marine renewable energy devices, predicting loads on marine structures, and in the study of open ocean wave generation and propagation in a realistic environment.

A fully non-linear numerical wave tank (NWT), based on Computational Fluid Dynamics (CFD), provides a useful tool for the analysis of coastal and offshore engineering problems. To generate and absorb free surface waves within a NWT, a variety of numerical wave maker (NWM) methodologies have been suggested in the literature. Therefore, when setting up a CFD-based NWT, the user is faced with the task of selecting the most appropriate NWM, which should be driven by a rigorous assessment of the available methods. To provide a consistent framework for the quantitative assessment of different NWMs, this paper presents a suite of metrics and methodologies, considering three key performance parameters: accuracy, computational requirements and available features. An illustrative example is presented to exemplify the proposed evaluation metrics, applied to the main NWMs available for the open source CFD software, OpenFOAM. The considered NWMs are found to reproduce waves with an accuracy comparable to real wave makers in physical wave tank experiments. However, the paper shows that significant differences are found between the various NWMs, and no single method performed best in all aspects of the assessment across the different test cases.

The wave resistance increase of a ship during its actual voyage can affect its speed and safety. To design ships with excellent sailing performance, it is necessary to accurately predict the wave resistance increase of a ship in waves, as well as the motion response and wave resistance prediction of ships in waves, which involves complex hydrodynamic problems. This paper first establishes a physical model of the KCS vessel, then utilizes the numerical wave tank platform independently developed by our university. Based on viscous flow theory, it calculates the resistance of the KCS under calm water conditions. Using three-dimensional potential flow methods and spectral analysis, it computes the wave-induced resistance values for the KCS under six-degree sea states, analyzes the wave-induced resistance performance of the KCS, and ultimately, based on the calculation results of calm water resistance and wave-induced resistance combined with propeller efficiency parameters, calculates the effective power of the engine.

The accurate generation of a target sea state in numerical or experimental wave tanks is a fundamental line of research for the ocean engineering community. It guarantees the quality and relevance of wave–structure interaction tests. This study presents a reproducible irregular wave generation and qualification procedure, accounting for the nonlinear aspects of wave propagation. It can be used for both numerical simulation and experiments. The presented numerical and experimental results are obtained from the OpenFOAM solver and the Ecole Centrale Nantes wave tank facilities, respectively. The procedure comprises two steps: First, the wavemaker motion is calibrated numerically to generate the target wave spectrum at the position of interest. This is achieved with a wavemaker-equipped nonlinear potential flow solver. The open-source HOS-NWT solver, based on the high-order spectral method, was employed in this study. Then, the corrected wavemaker motion is used directly in the experimental wave tank. OpenFOAM simulations were performed to generate waves with the relaxation method, using wave elevation and velocity field data from HOS-NWT. The procedure was finally tested for mild and extreme breaking sea states. The waves generated by the HOS-NWT solver, the experiment, and the OpenFOAM simulation were compared from both stochastic and deterministic perspectives.

In naval and ocean engineering, accurate simulation of incident waves is essential for predicting the motion response of offshore structures. Traditional wave generation methods, such as piston- and flap-type wave makers, often face challenges in accurately replicating the orbital motion of water particles beneath the free surface, which can limit their applicability in high-fidelity simulations. In this study, a numerical investigation is conducted to compare the performance of piston-type, flap-type, and double-flap-type wave makers using STAR-CCM+2310(18.06.006-R8). The influence of water depth on wave height accuracy is evaluated across different measurement locations within a numerical wave tank. Theoretical analysis of wave generation mechanisms is incorporated to clarify the applicability limits of linear theory and to better interpret the numerical results. Results indicate that, under the tested two-dimensional CFD conditions, the double-flap-type wave maker tended to provide closer agreement with theoretical predictions, particularly at greater depths, compared with conventional methods. These findings suggest potential advantages of the double-flap configuration and provide insights for refining wave generation techniques in numerical and experimental wave tanks, thereby supporting more reliable hydrodynamic analyses of floating structures.

This paper aims to investigate numerically linear stable waves at low wave steepness in shallow water using ANSYS Fluent software. The authors mainly determined how, when, and where a linear wave will reach its stable state in shallow water. The finite volume method is used to solve the Navier-Stokes equations. The inflow velocity method and the Dirichlet boundary condition are used to generate a suitable linear wave. Numerical damping is used at the end of the tank to reduce the reflection of the wave. The accuracy and stability of the waves are judged under wave height variation between the CFD results and the analytical results. The test has been conducted in four different cases (Case 1, Case 2, Case 3, and Case 4). Wave evolution and particle velocity are obtained in the velocity field to understand the wave stability in the numerical wave tank. Numerical data are captured from the free surface to compare the surface profile and wave velocity. The results have revealed that the accuracy, stability, and consistency of the linear waves are in good agreement with the analytical solution. The relative error between the two results is 1.43% for Case 3. This research is a highly relevant source of information in realistic wave generation to design various practical systems such as wave energy converters, offshore marine structures, and many ocean engineering problems‎.

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.

Min, E.-H. and Koo, W., 2021. Numerical analysis of nonlinear wave characteristics under porous sloped-seabed conditions. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 116–120. Coconut Creek (Florida), ISSN 0749-0208. The characteristics of nonlinear wave attenuation were analyzed under porous sloped-seabed conditions. Nonlinear wave propagation was simulated in the time domain using a two-dimensional fully nonlinear numerical wave tank (NWT). The NWT technique was based on the boundary element method and consisted of two computational domains: A fluid domain and a porous seabed domain. To account for the wave-porous subsea interaction, the boundary value problem was solved in each domain, and the calculated values were exchanged at the interface boundary between the fluid domain and the porous domain at each time step. The shoaling coefficients for wave propagation on a sloped-seabed were calculated, and the attenuation of the waves due to interaction with the porous bottom was investigated. Waves traveling to the coast were decomposed into each frequency component, and the magnitude of the wave attenuation ratio for each component was compared. The characteristics of wave propagation according to the permeability coefficients on the seabed, wave steepness, and wave periods were also investigated.

Extreme waves, also known as ‘rogue waves’, have posed considerable challenges to maritime traffic over some time. Efforts have been directed at investigating the mechanisms governing these extreme energy localizations in oceanic environments. Modulational instability, also known as sideband instability, is one such mechanism that has been proposed to explain the occurrence of such phenomena in the framework of non-linear theory. The current work is aimed at better understanding the effects of sideband modulations on the propagation of unidirectional waves. To achieve this, a numerical wave tank (NWT) has been constructed using Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) to investigate the different parameters associated with the generation and propagation of plane, modulated waves. General Process Graphics Computing Unit (GPGPU) computing has been utilized to accelerate the computational process and improve the computational efficiency. The chosen numerical scheme has been validated by carrying out irregular waves focusing simulations to compare with available experimental data. Additionally, a Peregrine-type breather experiment has also been performed as part of the validation studies to look at energy localization within the NWT. The effects of the different parameters associated with the modulations to a plane propagating wave have been investigated using a blend of surface elevation data, eigenvalue, and frequency spectra. The effect of water depth on the perturbations to plane waves has been also investigated. The observations from these experiments can help shed light into the effects of modulations in the propagation of plane waves and help in the study of oceanic energy localization studies in future.

Flood inundation and shoreline erosion have long occurred in Sayung, Demak area, the northern coast of Central Java Province, Indonesia. The people of Sayung planted mangroves to reduce the flood inundation and shoreline erosion in that area. They built the bamboo array to protect the juvenile mangroves from incoming waves. The bamboo acts as a breakwater and is considered an environmentally friendly permeable structure to reduce wave energy and stimulate sedimentation. This paper discusses three bamboo arrays’ effectiveness in wave reduction using Numerical Wave Tank (NWT). The interaction of regular waves with a permeable structure comprising a single row of vertical circular poles was conducted based on the Smoothed Particle Hydrodynamics (SPH) method. The effect of different waves and structural dimensions on the permeable structure was investigated based on the structure’s transmission coefficient (Kt) performance. The investigations have revealed that structures with the combination of Vertical-Horizontal formation (VH) attenuate more wave energy than Vertical Only (VO) and the combination of Vertical-Diagonal formation (VD). As the wave steepness increases, the transmission coefficient decreases. Likewise, the transmission coefficient (Kt) is decreasing when the wave height is increasing. On the other hand, the transmission coefficient (Kt) increases as the wave period increases. As the structure spacing ratio between end-to-end and center-to-center spacing (e/S) rises, the transmission coefficient (Kt) also increases. The diameter (D) has a slight effect on the transmission coefficient (Kt). However, the center-to-center spacing (S) has a more significant impact than the diameter on the transmission coefficient, affecting an inclination on the transmission coefficient (Kt) when center-to-center spacing (S) goes up.