• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.569-579
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• 2013

A steel-type breakwater that uses a submerged dual horizontal porous plate was originally proposed by Kweon et al. (2005), and its hydrodynamic characteristics and design methodology were investigated in a series of subsequent researches. In particular, Kweon et al. (2011) proposed a method of estimating the vertical uplift force that acts on the horizontal plate, applicable to the design of the pile uplift drag force. However, the difference between the method proposed by Kweon et al. (2011), and the wave force measured at a different time without a phase difference, have not yet been clearly analyzed. In this study, such difference according to the method of estimating the wave force was analyzed, by measuring the wave pressure acting on a breakwater model. The hydraulic model test was conducted in a two-dimensional wave flume of 60.0 m length, 1.5 m height and 1.0 m width. The steepness range of the selected waves is 0.01~0.03, with regular and random signals. 20 pressure gauges were used for the measurement. The analysis results showed that the wave force estimate in the method of Kweon et al. (2011) was smaller than the wave force calculated from the maximum pressure at individual points, under a random wave action. Meanwhile, the method of Goda (1974) that was applied to the horizontal plate produced a smaller wave force, than the method of Kweon et al. (2011). The method of Kweon (2011) was already verified in the real sea test of Kweon et al. (2012), where the safety factor of the pile uplift force was found to be greater than 2.0. Based on these results, it was concluded that the method of estimating the wave force by Kweon et al. (2011) can be satisfactorily used for estimating the uplift force of a pile.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.363-368
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• 2017

The tsunami flood the coastal cities and damage the land structures. The study on wave pressure and force on land structures is one of the important factors in designing the stability of inland structures. In this study, two - dimensional wave flume tests on the horizontal wave force and pressure of tsunamis on a simplified box-type structure was conducted. Vertical distribution and wave power of horizontal wave pressure over time were measured by pressure sensors and force transducer. Also, those were measured from the different wave breaking types. The vertical distribution of horizontal wave pressure was uniform at the moment when the horizontal wave force to the structure was maximum under the breaking wave condition. A surf similarity parameter was employed in order to figure out the relationship between the maximum horizontal wave force on the structure as a function of various incident wave conditions. As a result, the non - dimensionalized horizontal wave force tends to decrease exponentially as the surf similarity parameter increases.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.733-742
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• 2020

Taking the cylindrical float of the floating fence of a floating litter collection device as the research object, based on the shallow immersion characteristics of the cylindrical float, the Morison equation is modified, and the interaction between regular waves and the partially immersed horizontal cylindrical float is discussed in combination with scale model test. The results show that the modified Morison equation can accurately predict the wave force of the horizontal cylindrical float and reveal the influence of amplitude, immersion depth and period on the wave force of the cylindrical float. For partially immersed cylindrical floats, the wave force increases with the increase in wave height and decays with the increase in period. The positive value distribution of the wave force is larger than that of the negative direction, and the difference between the positive and negative directions is mainly affected by the immersion depth.

• Journal of Coastal Disaster Prevention
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• v.1 no.1
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• pp.28-35
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• 2014

This study investigated the applicability of four empirical equations (Morihira et al., 1967; Goda, 2010; Jensen, 1984 and Bradbury et al., 1988; Pedersen, 1996) suggested for estimating the horizontal wave force on the crown wall of sloping breakwaters. For the two exemplary cross sections of the breakwaters whose geometry are apparently different each other, the estimates of horizontal wave force calculated by the four equations were compared. The values of estimated wave force showed considerable discrepancy among the equations for each of the two exemplary breakwater cross sections, respectively. In addition, the relative magnitude of the wave force was quite different according to the breakwater geometry as well as the design wave condition. In general, Morihira's or Goda's formulae produced larger estimates of the horizontal wave force than Jensen/Bradbury's or Pedersen's formulae if the wave period (or wavelength) is comparatively short. In contrast, exactly opposite result was obtained when the wave period or wavelength is comparatively long. Further detailed study based on physical experiments is required to examine the applicability of the four empirical equations considered in this study more thoroughly.

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.3
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• pp.201-207
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• 2011

In this paper, we focused on computing the higher-harmonic components of the transmitted wave passing over a submerged circular cylinder to show that it is causing a horizontal negative drift force. As numerical models, a circular cylinder held fixed under free surface in deep water is adopted. As the submergence of a circular cylinder decreases and the incident wavelength becomes longer, the higher-harmonic components of the transmitted wave starts to increase. An increase of the higher-harmonic components of the transmitted wave makes the horizontal drift force be negative. It is also found that the higher-harmonic amplitudes averaged over the transmitted wave region become larger with the increase of wave steepness and wavelength as well as the decrease of submergence depth.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.474-478
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• 2004

Based on the recent laboratory experiments (Kim et al. 2004), comparisons of caisson sliding distance are made between the computations and experiments. The time history model of wave force, which is proposed by Tanimoto et al. (1996), is modified in the standing wave part of horizontal and uplift wave forces because of the overestimation of the time history model. The comparison between experimental and computational sliding distance has showed that the caisson tilting increases the resistant force to the horizontal sliding. Therefore, a titling resistant force, which is caused by caisson tilting, is introduced into computation of sliding distance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.3
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• pp.161-169
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• 2020

Physical experiments have been performed in a wave basin to investigate change of the wave loading on the crown wall under obliquely incident wave conditions. The measurement was carried out with wave incidence angle of 0, 15, 30 and 45°. The pressure transducers were placed on the front and bottom face of the crown wall to obtain horizontal and uplift force as well. It was found that both the horizontal and vertical force decreases with the incidence angle. Based on the analysis of the experimental data, a formula was suggested to estimate the reduction rate of horizontal and vertical forces under obliquely incident waves.

• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.443-450
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• 2014

The objective of this study is to examine the nonlinear fluid characteristics near and inside a moonpool in various sea conditions. We estimate the flow of the free surface in a moonpool taking into account the viscosity effect and the hydrodynamic forces that affects a moonpool and hull through CFD calculations. The comparison of horizontal forces per wave length shows that the hydrodynamic force is greater for the long wave length than short wave length, and the greatest hydrodynamic force acts on the moonpool when the wave length is equal to the ship's length. The horizontal force decreases as the wave amplitude decreases, and the hydrodynamic force acting on the moonpool in ${\lambda}=LBP$ is 10 times that in ${\lambda}=LBP/3$. The free surface demonstrates the piston mode, in which it oscillates up and down while remaining essentially flat, and the rise of the free surface level increases as the wave length increases. We can assume that the hydrodynamic force acting on the moonpool increases owing to the effect of a strong vortex for ${\lambda}=LBP$ and owing to the rise of the free surface level for ${\lambda}=LBP{\times}2$.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.5
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• pp.335-341
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• 2014

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.