• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.1
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• pp.60-73
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• 2014

The seaward reverse wave, occurring on the submerged dual porous horizontal plate, can contribute to the reduction of the transmitted wave as it reflects the propagating wave. However, the collision between the propagating and seaward reverse waves increases the water level and acts as a weight on the horizontal plate. This study investigated the characteristics of the wave pressure created by the seaward reverse wave through the analysis of experimental data. The analysis confirmed the following results: 1) the time series of the wave pressure showed reverse phase phenomena due to the collision, and the wave pressures acted simultaneously on both upper and lower surfaces of the horizontal plate; 2) the horizontal plate became repeatedly compressed and tensile before and after the occurrence of the seaward reverse wave; and 3) the seaward reverse wave created the total wave pressure to the maximum towards the direction of gravity, primarily on the upper plate. It was also confirmed that the wave distributions showed a similar trend to the wave steepness. Such outcome of the analysis will provide basic information to the structural analysis of the horizontal plate as a wave dissipater of the steel-type breakwater (STB).

• 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.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.321-332
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• 2021

The crown wall with parapet on top of the rubble mound breakwater represents a relatively economic and efficient solution to reduce the wave overtopping discharge. However, the inclusion of parapet leads to increased wave pressure on the crown wall. The wave pressure on the crown wall is investigated by physical model test. To design the crown wall the wave loads should be available, and the horizontal wave pressure is still unclear. Regarding to the horizontal wave pressure on the crown wall, a series of experiments were conducted by changing the rubble mound type structure and the wave conditions. Based on these results, pressure modification factors of Goda's (1974, 2010) formula have been suggested, which can be applicable for the practical design of the crown wall of the rubble-mound breakwater covered by tetrapods.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.469-480
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• 2022

To design the crown wall of rubble-mound breakwaters, the horizontal wave load should be available, but determining this load remains difficult. Lee et al. proposed modification factors for Goda's formula for the horizontal wave pressures on acrown wall. The empirical formula by Lee et al. was based on a two-dimensional model test with a relatively narrow armour crest width in front of the crown wall. In this study, a series of experiments at the same facility were conducted on the horizontal wave pressures on the crown wall of a rubble-mound breakwater with a wide armour crest width. As a result, the pressures of the unprotected part of the crown wall were nearly identical to the narrow crest width. However, the pressures of the protected part tended to decrease with a change in the armour crest width. From the experimental results, the horizontal pressure modification factors of Goda's formula including the armour crest width effect are suggested here and are likely applicable to practical designs of the crown walls of rubble-mound breakwaters covered with tetrapods.

• Nuclear Engineering and Technology
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• v.28 no.4
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• pp.379-389
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• 1996

To experimentally investigate the several wave patterns for the horizontal countercurrent stratified air-water flow, a series of systematic experimental studies have been performed. The experiments are carried out in a horizontal pipe with 4m in length and 102mm in inner diameter. The oater and air superficial velocities vary from 0.0004 to 0.0204 and from 0 to 6m/s, respectively. The instantaneous water thickness is measured by parallel-wire conductance probes, and the wave field is recorded by high speed video camera. Also, to evaluate the wave effect on interfacial friction factor, the pressure drop is measured. Statistical data anal)sis is accomplished in order to obtain the fundamental wave parameters such as un amplitude, length and velocity, and spatial growth factor. By using these statistical parameters, the wave regime boundaries can be verified.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.119-128
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• 2015

This study investigates the wave pressure characteristics of the pile-supported breakwater with single or double perforated walls through 2-D hydraulic experiments and the measured wave pressures are compared to those of wave pressures by Goda's formula. For single chamber, the measured wave pressures in the front wall and rear wall decreased to about 25% and 30%, respectively, compared to those of wave pressures by Goda's formula. Also, the decrease in the wave pressures for double chamber were about 27%, 53%, and 64% in the front wall, middle wall, and rear wall, respectively. It was found that the pile-supported breakwater with double perforated walls was more efficient than the single chamber due to wave dissipation effects of double slit walls with horizontal slits.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.6 no.1
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• pp.7-14
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• 2003

The interaction of monochromatic incident waves with a submerged horizontal porous membrane is investigated in the context of two-dimensional linear hydro-elastic theory. It is assumed that the membrane is made of material with very fine pores so that the normal velocity of the fluid passing through the porous membrane is linearly proportional to the pressure difference between two sides of the membrane (e.g. Darcy's law). Using the Eigen-function expansion method, the wave-blocking performance of a submerged horizontal porous membrane is tested with various membrane tensions, porosities, lengths, and submerged depths. It is found that an optimal combination of design parameters exists for given water depth and wave characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.90-96
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• 2009

Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multi-regression analysis in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

• Ocean Systems Engineering
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• v.12 no.4
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• pp.439-459
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• 2022

This paper describes experimental studies of impact pressure generated by breaking regular waves in shallow water on a vertical cylinder. Experimental work was carried out in a shallow water flume using a 1:30 - scale model of a vertical rigid circular hollow cylinder with a diameter 0.2 m. This represents a monopile for shallow water offshore wind turbines, subjected to depth induced breaking regular waves of frequencies of 0.8 Hz. The experimental setup included a 1 in 10 sloping bed followed by horizontal bed with a constant 0.8 m water depth. To determine the breaking characteristics, plunging breaking waves were generated. Free surface elevations were recorded at different locations between the wave paddle to the cylinder. Wave impact pressures on the cylinder at a number of elevations along its height were measured under breaking regular waves. The depth-induced wave breaking characteristics, impact pressures, and wave run-up during impact for various cylinder locations are presented and discussed.