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Lee, W.D., Kim, I.H., Yoon, J.S., Cho, W.C. and Hur, D.S., 2016. Analysis of beach deformation according to nourishing sand in haeundae beach, Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1372 - 1376. Coconut Creek (Florida), ISSN 0749-0208. This study has analyzed the beach deformation characteristics of Haeundae Beach, which is one of the most representative beaches of S.Korea, after beach nourishment through monitoring and performing a numerical simulation. This study was able to analyze the beach deformation characteristics after beach nourishment in depth (e.g. variations in coastline, beach profile and the area and volume of beach, and beach stabilization process) in line with the results of marine geophysical survey (Do et al., 2015). This study surveyed the marine morphological changes around Haeundae Beach caused by Typhoon Neoguri, but morphological changes did not show in the water level of over 3m. In addition, this study was not only able to identify the short-term advance and retreat of coastline in the beach profile due to Typhoon Neoguri, but also understand this phenomenon on the basis of the results of wave field analysis using Numerical Wave Tank (NWT). Furthermore, this study was able to find that NWT and the coupling calculation of Contour-line model simulated the changes of coastline due to Typhoon Neoguri almost similarly. NWT and the coupling calculation of Contour-line based on long-term monitoring are expected to greatly contribute to understanding the beach deformation characteristics due to beach nourishment in future.

Jeong, Y.-M.; Jeon, H.-S.; Jeong, Y.-H., and Hur, D.-S., 2023. Numerical study on early sand movement in front of a coastal revetment using the NWT-DEM two-way coupled model. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 51-55. Charlotte (North Carolina), ISSN 0749-0208. The two-way coupled analysis of a particle method and a wave field model was conducted to examine numerically the characteristics of early sand movement in front of a coastal revetment. The coupled model used in this study can not only consider the interaction among the wave, coastal revetement, and ground but also represent early sand movement in front of coastal revetment under waves. The validity and usefulness of a particle method of Discrete Element Method (DEM) was ensured by comparing angle of repose for quartz sand with the results of a hydraulic experiment. The early sand movement occurring in front of coastal revetment was numerical compared using the two-way coupled model with early sand behavior amount caused by the reflected wave and the interaction between the wave, coastal revetment, and ground. In general, as the exposure of the coastal revetment to the waves increases, the scour depth in front of the structure increases. The maximum scour depth increases by 9 to 150% depending on the locations of the coastal revetments considered in this study. Moreover, the active sand movement in front of coastal revetment and the exposure and leakage of the terrain base at large scour depths can ultimately cause collapse and safety problems. Thus, the wave-particle interaction analysis of this study can be a numerical analysis for examining safety owing to sand movements caused by waves in front of coastal revetment.

Regular wave-induced behaviour of a floating stationary two-dimensional body with a moonpool is studied. The focus is on resonant piston-mode motion in the moonpool and rigid-body motions. Dedicated two-dimensional experiments have been performed. Two numerical hybrid methods, which have previously been applied to related problems, are further developed. Both numerical methods couple potential and viscous flow. The semi-nonlinear hybrid method uses linear free-surface and body-boundary conditions. The other one uses fully nonlinear free-surface and body-boundary conditions. The harmonic polynomial cell method solves the Laplace equation in the potential flow domain, while the finite volume method solves the Navier–Stokes equations in the viscous flow domain near the body. Results from the two codes are compared with the experimental data. The nonlinear hybrid method compares well with the data, while certain discrepancies are observed for the semi-nonlinear method. In particular, the roll motion is over-predicted by the semi-nonlinear hybrid method. Error sources in the semi-nonlinear hybrid method are discussed. The moonpool strongly affects heave motions in a frequency range around the piston-mode resonance frequency of the moonpool. No resonant water motions occur in the moonpool at the piston-mode resonance frequency. Instead large moonpool motions occur at a heave natural frequency associated with small damping near the piston-mode resonance frequency.

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.

Hur, D.-S; Shin, S.; Lee, S.-Y., and Jeong, Y.-M., 2023. Analysis of shoreline change due to the installation of hybrid coastal structure with Submerged Aquatic Vegetation (SAV). In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 638-642. Charlotte (North Carolina), ISSN 0749-0208. Recently, they have been designed and constructed as a complex defense method to protect the beach with nourishment. In this study, the Submerged Aquatic Vegetation (SAV) among the soft defense methods (Hybrid coastal structure), which are more flexible than the hardness method, is compared and evaluated with the conventional method. The numerical analysis method used is a 3D numerical model based on the Navier–Stokes equation and can be used to analyze the 3D hydraulic characteristics of the method to address coastal erosion. Based on the results, the N-line model, a model that depicts coastline changes, can be used for comparison. The effectiveness and validity of the numerical model were examined by comparing and analyzing its results with those of the existing hydraulic experiment. The model accurately reproduced the quantitative and qualitative changes in the shoreline behind the structure, as well as the change in wave height due to the wave control function of the Submerged Breakwater (SB). As a result, changes to the waves and stratified nearshore currents owing to 3D fluid movement in surrounding waters can be confirmed using the existing hardness method used to respond to coastal erosion, and the hydraulic characteristics are analyzed and compared with the conventional method using the wave control characteristics of the installed vegetation zone. Furthermore, the wave-breaking height and the wave-breaking direction are examined from the results based on the 3D hydraulic characteristics of the vegetation zone and the conventional hardness method to compare the shoreline changes. Compared with the existing hardness method, the change in the wave breaking direction is lower owing to the wave control capability of the SAV resulting from the drag coefficient of vegetation, leading to the advance of the shoreline being relatively small.

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.

This study analyzes the hydrodynamic performance of a V-type wave dissipation system and amphibious landing equipment under different combined fields using the Reynolds-averaged Navier–Stokes (RANS) method. A three-dimensional numerical wave tank is established to simulate regular waves and validate the performance of an airbag-type floating breakwater. This study evaluates the optimal hydrodynamic performance of a V-type wave dissipation system under various configurations in a wave-only field and subsequently compares the efficacy of the better-performing system across multiple environmental conditions. The results show that the V-type wave dissipation system in the configurations of 30° and 45° angles is more favorable for the flow field and the amphibious landing equipment behind it. Compared to the wave-only condition, the time histories of wave heights under both wave-current and wind-wave conditions present an obvious phase advancement. In the wave-current field, a following current reduces the wave height and shortens the wave period. Conversely, in the wind-wave field, a following wind velocity leads to a certain increase in wave height while exerting minimal impact on the wave period. Compared to the wave-only condition, the peak and trough values of the wave height monitoring points in the combined wind-wave-current field show an increasing trend, with a significant increase in resistance and a shorter resistance period for the amphibious landing equipment behind the V-type wave dissipation system. This study shows that the selected V-type wave dissipation system proves to be more effective in wave-only and wave-current conditions, providing valuable references for the engineering application of this system.

To address the lack of efficient flexible protection measures for ocean engineering equipment operating in complex coupled wind–wave–current environments, this study develops a coupled “flexible wave-dissipating system” numerical model based on a validated three-dimensional numerical wave tank. The model is used to investigate, under both regular and irregular wave conditions, the influence of different wind and current incidence angles and the presence or absence of the breakwater on wave propagation and hydrodynamic responses. By comparing the significant wave height, transmission coefficient and wave dissipation efficiency in the sheltered region along with the drag force and free-surface pressure, the wave-attenuation and load-reduction performance of the flexible breakwater is quantitatively evaluated. The results demonstrate that deploying a flexible breakwater can significantly attenuate wave energy in the sheltered region, enhance wave dissipation efficiency, and reduce the transmission coefficient, thereby concurrently decreasing both the drag force and free-surface pressure. Under both wind and current conditions, the maximum loads occur at 0° head-on incidence. However, under 30° oblique wind–wave action, the flexible breakwater yields the most pronounced increase in dissipation efficiency compared to the case without a breakwater. A stable correlation is observed between dissipation efficiency and hydrodynamic loads, which can serve as a unified evaluation metric for assessing the protective performance of flexible breakwaters in ocean engineering applications.

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.