Maximum Wave Force Research Articles

Evaluation of the Hydraulic Performance of a Rear-Parapet Vertical Breakwater under Regular Waves through Hydraulic Experiments

Climate change has resulted in increased intensity and frequency of typhoons and storm surges. Accordingly, attention has been paid to securing the breakwater’s stability to protect the safety of the port. Herein, hydraulic model experiments were conducted to evaluate the hydraulic performance of a vertical breakwater having a rear parapet. For comparison, cases in which the parapet was placed on the seaside, the harborside, and at the center of the breakwater were considered. Regular waves were used for convenient performance analysis. Five wave gauges and nine pressure transducers were installed to secure physical data for hydraulic performance evaluation. Results showed that a rear parapet can reduce the maximum wave force acting on the breakwater. Even though impulsive pressure was generated, it did not affect the stability of the breakwater owing to the phase difference between the maximum wave pressures acting on the caisson and parapet. By decreasing the maximum wave force, the required self-weight that satisfies the safety factor of 1.2 was reduced by up to 82.7%; the maximum bearing pressure was reduced by up to 47.6% compared with that of the parapet located on the seaside. Thus, the rear parapet was found to be more suitable for actual applications.

Numerical investigations of wave loads on fixed box in front of vertical wall with a narrow gap under wave actions

Violent fluid oscillations may appear inside the narrow gap between multiple structures in close proximity and cause severe damage to such structures and safe operations. Here, based on the OpenFOAM® package, this paper presents a numerical investigation of wave loads during gap resonance between a fixed box and a vertical wall by utilizing a two-dimensional (2D) numerical wave flume. The box-wall system is subjected to incident regular wavesco with various wave heights and frequencies. The topographies of plane slopes with various inclinations are arranged in front of the vertical wall. This paper focuses on the influences of the topographical variation on the wave loads, including the horizontal wave force, the vertical wave force and the moment on the box. It is found that all the frequencies, at which the maximum horizontal wave force, the maximum vertical wave force and the maximum moment appear, decrease with the increase of topographical slope, S, overall. Moreover, these frequencies are also shown to deviate from the fluid resonant frequency to different degrees. For all the incident wave heights considered, both the maximum horizontal wave force and the maximum moment present a pattern of fluctuation with the topographical slope.

Physical Modeling of Horizontal and Vertical Tsunami Forces on the Elevated Overland Structure

Park, H.; Cox, D.T., and Shin, S., 2019. Physical modeling of horizontal and vertical tsunami forces on the elevated overland structure. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 51-55. Coconut Creek (Florida), ISSN 0749-0208.In this study, two-dimensional hydraulic model tests were conducted to investigate the characteristics of the force of tsunami waves on the simplified box-type elevated structure. The vertical elevation of the structure was changed to investigate the relation between the wave force and the air gap. The tsunami waves were generated by using the error function with the full-stroke of the wave paddle to maximize inundation. The horizontal and vertical wave forces and pressures on the structure by the tsunami waves were measured, and the relation between the maximum wave force, air gap and the incident wave condition was derived. Using the measured maximum horizontal wave force from the different wave conditions, the empirical formula of the non-dimensionalized horizontal wave force as a function of the surf similarity parameter was obtained. It was found that the horizontal wave force is inversely proportional to the surf similarity parameter in the case of the unelevated structure. The experimental results also showed that the ratio of the horizontal force to the vertical force is larger in the case of broken and breaking wave conditions in the case of the elevated structures.

Reliability Analysis of the Long Caisson Breakwater considering to the Wave Force Reduction Parameter

Lee, G. N.; Lee, I. K., and Kim, D. H., 2018. Reliability Analysis of the Long Caisson Breakwater Considering to the Wave Force Reduction Parameter.. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1246–1250. Coconut Creek (Florida), ISSN 0749-0208.If a breakwater is longer than a full design wave, maximum design wave force does not attack over the full span of the breakwater. Therefore, design wave load can be decreased compared with short modular caisson. This study is to grasp the influence of the wave force reduction effect on the failure probability and to confirm how much the stability is secured compared with the existing modular breakwater. Therefore, reliability analysis of long caisson breakwater and existing modular caisson breakwater was performed. As a result, the reliability index of the long caisson breakwater was higher than that of the existing modular caisson breakwater, and it was confirmed that the significant wave height of the design variables had the highest influence. In addition, the reliability analysis was performed according to the change of the mean value of the variables used in the calculation of the wave force reduction parameter. It is confirmed that the relationship between each variable value and the wave force reduction parameter appears in the analysis results.

Theoretical and experimental investigation on wave interaction with a concentric porous cylinder form of breakwater

This paper aims at deriving velocity potential for the regular wave passing through a concentric porous cylinder system, which has an arbitrary smooth section. The wave interaction with the structures, for instance wave force on them and wave elevation, are discussed with different sections and wave properties in this study. The efficiency and accuracy of present method was validated by comparing with the semi-analytical method of SBFEM first. Then an experiment with a quasi-ellipse caisson was also performed to demonstrate the effectiveness and practical potential of present method. Finally, a surface-piercing concentric cylindrical system, which consists of an impermeable inner cylinder and a coaxial single-layered perforated cylinder, was investigated by using present method. The analysis shows that the maximum wave force on the inner cylinder is reduced to some extent with a noncircular perforated cylinder around it, compared with circular cases, while the wave run-up is enlarged by the uneven spacing between the boundaries with the increasing of the wave number.

Hydroelasticity and nonlinearity in the interaction between water waves and an elastic wall

The present study investigates the role of hydroelasticity and nonlinearity in the fundamental problem of the interaction between non-breaking water waves and an elastic wall. To this end, two interaction scenarios are considered: the interaction of a rigid wall supported by springs and a pulse-type wave, and the interaction of an elastic deformable wall and an incident wave group. Both of these scenarios are numerically simulated in a computational domain representing a two-dimensional wave flume. The simplicity of the domain enables one to perform highly efficient simulations using the high-order spectral method (HOSM). Wave generation at the flume entrance and the wave–wall interaction at the flume end are simulated by means of the additional potential concept. In this way, the efficiency that characterizes the original HOSM is preserved for the present non-periodic problems. The investigation of the first scenario reveals the influence of the wall’s dynamical response on the hydrodynamic values. The results show that the maximum wave run-up and wave force are prominently fluctuating around the values corresponding to a fixed wall as a function of the wall’s eigenfrequency, revealing regions of relaxation and amplification. The second scenario studies the effect of the nonlinear evolution of the incident wave group. The high-order wave harmonics generated during the group evolution are found to be significant for predicting extreme hydrodynamic and structural values, and may result in resonant interactions in which hydroelasticity appears to play an important role.

Two-Dimensional Analysis of Cable Stayed Bridge under Wave Loading

In the present study finite element analysis is performed for a modified fan type cable-stayed bridge using ANSYS Mechanical. A cable stayed bridge with two towers and main deck is considered for the present study. Dynamic analysis is performed to evaluate natural frequencies. The obtained natural frequencies and mode shapes of cable stayed bridge are compared to the existing results. Further studies have been conducted for offshore area application by increasing the pylon/tower height depending upon the water depth. Natural frequencies and mode shapes are evaluated for the cable stayed bridge for offshore area application. The results indicate that the natural periods are higher than the existing results due to the effect of increase in mass of the structure and decrease in stiffness of the pylon/tower. The cable stayed bridge is analyzed under various environmental loads such as dead, live, vehicle, seismic and wave loading. Morison equation is considered to evaluate the wave force. The sum of inertia and drag force is taken as the wave force distribution along the fluid interacting height of the pylon. Airy’s wave theory is used to assess water particle kinematics, for the wave periods ranging from 5 to 20 s and unit wave height. The maximum wave force among the different regular waves is considered in the wave load case. The support reactions, moments and deflections for offshore area application are highlighted. It is observed that the maximum support reactions and support moments are obtained due to wave and earthquake loading respectively. Hence, it is concluded that the wave and earthquake forces shall be given significance in the design of cable stayed bridge.

Numerical Investigation of Extreme Wave-Induced Loading on Box Girder in Marine Environment

In this paper, a 2D numerical model for wave-girder interaction was proposed to estimate the maximum wave forces on the box girder of a coastal bridge under extreme wave conditions. The Reynolds Averaged Navier-Stokes (RANS) equations were applied to simulate water wave motion and the Volume of Fluid (VOF) method was used to track the free surface. In this study, the developed 2D numerical model was validated by first comparing with experimental data. Then, a set of parametric studies was conducted to examine the effects of the wave heights, wave periods, water depths and submerged coefficients on the wave force on the box girder under extreme wave conditions. Finally, a function to predict the extreme wave-induced forces on the box girder under various wave conditions was proposed for engineering practice.

Numerical simulations and experimental visualizations of the vortex characteristics for a solitary wave interacting with a bottom-mounted vertical plate

This study is aimed to investigate numerically and experimentally the interaction of a solitary wave with a bottom-mounted vertical thin plate with focuses on the wave induced fluid kinematics and vortex flow patterns. A streamfunction–vorticity free-surface (SVFS) based fully nonlinear viscous wave model solved in a transient boundary-fitted coordinate system with locally overlaid grids is applied to study this wave-plate interaction problem. Qualitative comparisons between numerically generated flow patterns around the plate and the experimental observations, including images from both the particle-tracking and the laser-dye visualization methods, are presented. The shear-layer velocity profiles are compared quantitatively with the experimental measurements. The detailed flow characteristics and formed vortices including the effect of the shape of the plate top on the vortex formation and development are numerically investigated. For a thin vertical plate, the flow characteristics that are affected by the dimensionless parameters of incident-wave height and plate height are also investigated. The numerical visualizations illustrated by the virtual transport of particle-tracing, streamlines, and equi-vorticity lines are useful to understand the kinematic behaviors of the induced vortical motions. Furthermore, the pressure gradient, shear stress, and maximum wave force are examined to detail the hydrodynamic impacts on the submerged plate.

Computational Fluid Dynamics Simulations of Regular and Irregular Waves Past a Horizontal Semi-Submerged Cylinder

Two-dimensional (2D) numerical simulations have been performed to investigate both regular and irregular waves past a fixed horizontally semisubmerged circular cylinder. The 2D simulations are carried out by solving Navier–Stokes equations discretized by finite volume method. Volume of fluid (VOF) method is employed to capture the free surface in the numerical wave tank (NWT). Validation studies have been performed by comparing the numerical results of free surface waves past the cylinder with the published experimental and numerical data. The present numerical results are in good agreement with both the experimental and the other numerical results in terms of hydrodynamic forces and free surface elevation. Subsequently, the effects of the wave height and the wavelength on wave–structure interaction are investigated by conducting numerical simulations on the regular and the irregular waves past a semisubmerged cylinder at different wave heights and the wavelengths. The averaged and maximum vertical wave forces on the cylinder increase with the increasing wave height. The numerical results for the irregular waves are compared with those induced by the regular waves in terms of the maximum and averaged vertical wave forces. When the significant wave height and the spectral peak period of the irregular waves are equal to the wave height and the wave period of the regular waves, the maximum vertical wave force induced by the irregular waves is larger than that induced by the regular waves, meanwhile, the average vertical wave forces have the contrary relationship.

Breaking wave interaction with a vertical cylinder and the effect of breaker location

The open-source CFD model REEF3D is used to simulate plunging breaking wave forces on a vertical cylinder. The numerical results are compared with data from the experiments carried out at the Large Wave Channel, Hannover, Germany to validate the model. Further, the location of the cylinder is changed so that the breaking wave impacts the cylinder at different stages of wave breaking and the resulting wave forces are evaluated. The different locations for the cylinder placement based on the breaker location are determined from the results obtained for the wave breaking process in a two-dimensional numerical wave tank. Maximum wave forces are found to occur when the breaking wave tongue impacts the cylinder just below the wave crest in all the cases simulated and the lowest wave forces are generally obtained when the wave breaks behind the cylinder. Several wave features such as the splashing on impact, the splitting and rejoining of the wave around the cylinder resulting in a chute-like jet formation are identified. The model provides a good representation of the breaking wave process and can be a useful tool to evaluate breaking wave forces on structures.

Evaluation of wave loads on a new type of perforated caisson

A new type of perforated breakwater has been tested combining the advantages of cylindrical geometry with stepped wave energy dissipation. Thus, the new type of caisson implies a significant reduction of maximum wave forces, as well as loads transmitted to the foundation in comparison with conventional vertical breakwater and other types of perforated caissons. Starting from a brief description of the model and test results, this paper describes the development of a methodology for the estimation of maximum wave loads on this type of breakwater, in order to become a generalisable tool for predesign purposes. Construction and installation constraints of this new type of caisson are also assessed. These need to be taken into account in order to keep some advantages from the proposed design, while noting the key factors from a practical point of view.

Dispersion Characteristics of Wave Forces on Interlocking Caisson Breakwaters by Cross Cables

Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.

Analytical solution of hurricane wave forces acting on submerged bridge decks

Hurricane waves are catastrophic disasters that cause damage to coastal bridges with insufficient clearance. This study presents an analytical method to estimate the wave forces acting on a submerged bridge superstructure during a hurricane based on the potential flow approach. The boundary value problem of the submerged bridge deck under wave action is analyzed first, and the mathematical formula for the analytical solution is derived using the eigenfunction matching method. To validate the effectiveness of the analytical model, results are compared to test data from two hydrodynamic experiments on the wave action of bridge decks. Finally, the AASHTO model is discussed, and a simple method for estimating the maximum horizontal and vertical wave forces is proposed. The analysis results indicate that the proposed analytical model can be used effectively for prediction of the maximum wave forces acting on a submerged bridge superstructure during hurricane waves.

Armor stability of hardly (or partly) reshaping berm breakwaters

This paper deals with stability of hardly (or partly) reshaping berm breakwaters. A simple physical argument is used to derive a new stability formula based on the assumption that the maximum wave force causing damage of armor layer is proportional to the maximum wave momentum flux near the structure toe. The main goal of the present paper is to provide an estimation technique based on this physical principle to predict the deformation of the front slope in terms of the eroded area. The proposed method is verified by comparison with model test data. It is found that by using the maximum wave momentum flux approach the damage to the front slope (eroded area) can be very well predicted. Moreover, a simple method to estimate the eroded area based on measured or calculated berm recession (Rec) and depth of intersection of reshaped and initial profile (hf) is presented. The performance of the simple method based on measured data of Rec and hf is better than the presented stability equation based on wave momentum flux parameter. When using the best prediction formulae for recession and depth of intersection the simple method and the momentum flux stability equation provide similar uncertainty.

津波入射波の形状が橋梁上部構造に作用する津波波力に及ぼす影響

In the Tohoku-Pacific Ocean Earthquake, many bridges were washed away by the tsunami. In the future, countermeasure for tsunami disaster will be needed, and the evaluation of tsunami wave force acting on bridges will be very important. This paper discusses the hydrodynamic tsunami-induced force acting on a bridge superstructure based on hydraulic model experiments. The results showed that tsunami wave forces were different according to the shape of tsunami incident wave and it was confirmed that maximum wave forces could be expressed by a function of the wave front slope of tsunami incident wave.

DISPERSION OF WAVE FORCES ON CAISSON BREAKWATERS USING INTERLOCKING SYSTEMS

Interlocking caisson-type breakwaters have recently gained attention for enhancing the stability of the conventional breakwaters. In this study, the dispersion characteristics of wave forces using interlocking systems connecting the upper part of caissons with cables in the normal direction of breakwaters were investigated. Based upon numerical experiments, the higher wave forces are transmitted through the cable as the angle of incident wave increases, while the maximum allowable wave force was capable of being increased by sharing the wave forces with the adjacent caissons. It was also found that the larger the stiffness of the interlocking cable, the larger the wave-dispersion effect.

단일 및 이중유수실 유공케이슨 방파제에 작용하는 최대 수평파력 비교

Physical experiments were carried out to measure the wave force on the vertical walls of perforated breakwater considering several phases of a wave acting on the breakwater. The maximum horizontal wave force acting on each vertical wall was compared between single and double chamber caisson breakwater. The experimental data in this study showed that the total horizontal wave force for double chamber caisson was 9.6% smaller on average than that for single chamber caisson when the total chamber width was the same for both caissons. Such reduction of the wave force is due to the dissipation of wave energy at the porous middle wall, which is located between the porous front wall and non-porous rear wall. 핵심용어: Perforated caisson breakwater, Double chamber, Middle wall, Wave force, Physical experiment, 케이슨 ë°©íŒŒì œ, ì´ì¤‘ìœ ìˆ˜ì‹¤, 중간벽, íŒŒë ¥, 수리모형실험

EXPERIMENTAL INVESTIGATION OF HORIZONTAL WAVE FORCES ON THE PERFORATED CAISSON WITH SINGLE AND DOUBLE WAVE CHAMBERS

The horizontal wave force acting on vertical walls of perforated caisson breakwater was experimentally investigated in this study. The maximum horizontal wave force acting on single and double chamber caisson was measured respectively and compared each other. By analyzing the obtained experimental data, it was clarified that the total horizontal wave force for double chamber caisson was 9% smaller on average than that for single chamber caisson when the total chamber width was the same for both caissons. The reason for such reduction of horizontal wave force on the double chamber caisson is found from additional dissipation of wave energy at the porous middle wall of the structure, by which rather impulsive wave force on the rear wall could be slightly diminished compared to the single chamber caisson.

陸上構造物を考慮した遡上計算結果を用いた津波波力算定方法の適用性

The estimation method of tsunami wave force acting on a land structure using hydraulic quantities around the structure was newly proposed in this study. Hydraulic experiments were conducted to estimate tsunami wave force acting on the structure. A 2D depth-integrated flow simulation under the installation of a land structure was carried out to examine run-up tsunami deformation. Even though the maximum wave force due to the initial impact of the leading edge on the structure cannot be reproduced by the proposed method, the method could reasonably estimate the tsunami wave force. Tsunami wave forces calculated by CADMAS-SURF/3D were in good agreement with the experimental results on the wave condition that cannot be reproduced by the evaluation method using the 2D simulation results.