• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.220-226
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• 2001

It is important to estimate exactly wave forces acting on various types of offshore structures under the severe environmental conditions in the ocean site. This paper presents an easy experimental method which deals with transient waves. The proposed scheme made it possible to generate breaking waves at any position in the wave tank by changing the maximum slope of the component waves. The theoretical and experimental methods were investigated by generating concentrated waves which acted on a single and multiple cylinders. The waves forces increased rapidly when the models encountered breaking waves. The theoretical results underestimates the forces due to breaking waves. Therefore, the effects due to breaking waves should be considered carefully in the design process of a structure under the influence of breaking waves.

• 한국해양공학회지
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• 제15권4호
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• pp.8-13
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• 2001

It is important to estimate exactly wave forces acting on various types of offshore structures under the severe environmental conditions in the ocean site. This paper presents an easy experimental method which deals with transient waves. The proposed scheme made it possible to generate breaking waves at any position in the wave tank by changing the maximum slope of the component waves. The theoretical and experimental methods were investigated by generating concentrated waves which acted on a single and multiple cylinders. The waves forces increased rapidly when the models encountered breaking waves. The theoretical results underestimates the forces due to breaking waves. Therefore, the effects due to breaking waves should be considered carefully in the design process of a structure under the influence of breaking waves.

• 한국해안해양공학회지
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• 제8권1호
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• pp.37-43
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• 1996

본 논문에서는 2차원 수조의 임의 지점에서 쇄파를 만드는 실험방법에 대하여 논하였다. 쇄파를 만들기 위해서 임의의 지점에 각 성분의 파정이 모이도록 위상차를 갖는 선형파를 합성하여 조파기를 작동시켰다. 또한 조파판의 운동진폭을 조절하여 다양한 파기울기에 대하여 실험을 수행하였다. 실험 결과 운동진폭이 너무 작은 경우에는 쇄파현상이 일어나지 않았고 불규칙한 파형만이 나타났으며, 최대파고가 H=0.0113g/T$^2$ 이상이어야 쇄파 현상이 나타남을 확인하였다. 쇄파의 모양은 대부분 경우에 spilling 형태였고, 특정한 운동진폭일 때 plunging 형태의 쇄파를 관찰할 수 있었다. 한편 비점성, 비압축성 유체로 가정하여 얻어진 경계적분방정식을 고차경계요소로 이산화하여 수치계산을 수행하였다. 자유표면의 처리를 위해서 Mixed Euler-Lagrangian 기법을 이용하였다 수치결과는 자유표면에서 주파수간의 상호간섭의 영향을 제대로 반영하고 있으며, 실험에서 계측한 파형을 제대로 모사하고 있음을 확인할 수 있었다.

• 한국해양환경ㆍ에너지학회지
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• 제5권1호
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• pp.11-18
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• 2002

방향 및 주파수 성분을 포함하는 파랑집중에 의해 다방향 쇄파를 생성하였으며, 등기울기 및 등진폭 스펙트럼 모델을 적용하였다. 생성된 다방향 쇄파는 초기쇄파, 단일쇄파 다중쇄파로 구분된다. 다방향 쇄파의 특성을 파정 기울기 및 비대칭성으로 정의되는 파형인자들의 함수로 고찰하였다. 또한 파랑집중의 효율성 관점에서 쇄파 파랑특성의 전개를 분석하였다. 파정 전면 기울기 및 연직 비대칭성은 쇄파과정에 영향을 미치는 중요한 인자이나, 파정후면 기울기 및 수평 비대칭성은 쇄파 과정에서 거의 상수 값을 갖는다. 방향 성분의 중첩은 파랑집중의 효율성을 크게 강화하며, 이는 다방향파의 쇄파 특성이 일방향파의 쇄파 특성과 상이함을 나타낸다.

• 한국해양공학회지
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• 제10권3호
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• pp.62-73
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• 1996

Numerical simulation is made of the three-dimensional wave breaking motion about a part of a floating offshore structure containing a circular cylinder mounted vertically onto a lower hull in regular periodic gravity wave generated by a numerical wave maker. TUMMAC-VIII finite-difference method is newly developed for such a problem. By use of density-function technique the three-dimensional wave breaking motion is approximately implenented in the framework of rectangular grid system. A porosity technique is devised for the implementation of the no-slip bydy boundary conditions. The generation of breaking waves by the interaction of incident waves with the structure is well simulated and interesting features of breaking waves are revealed with containing degree of quantitative and qualitative accuracy.

• Ocean Systems Engineering
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• 제12권4호
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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.

• 수산해양기술연구
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• 제48권3호
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• pp.227-234
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• 2012

This paper describes the remote monitoring of breaking ocean waves generated by Typhoon Nabi, whose name means butterfly in Korean, using a marine X-band radar in the Yongho Man, Busan, Korea. The basic purpose of this study is to investigate the dynamic behavior and to estimate the periods of breaking waves across the surf zone from radar image sequences. In these experiments, the land-based radar system imaged the inshore zone of three miles from the coastline to a isobath of 30 meters. The wave period and the dominant wave direction for breaking ocean waves extracted directly from radar image sequences were 157.4 meters and 298 degrees, respectively. However, the result calculated quantitatively by the continuous wavelet transform (CWT) showed that the period of breaking waves was 154.3 meters. The average difference in breaking wave periods between the value extracted by using EBRL (electronic bearing and range line) of radar and the calculated value by CWT was 3.1 meters, showing that the CWT method is also accurate. These results suggest that a marine X-band radar system is a viable method of monitoring the breaking ocean waves.

• 한국해안해양공학회지
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• 제4권3호
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• pp.178-186
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• 1992

어떤 특정 위치에서 파속이 빠른 파가 느린 파를 추월하도록 여러가지 다른 주파수의 파를 중첩시킴으로써 심해쇄파에 대한 실험을 수행하였다. 예상 쇄파지점 근처에서 큰 파고를 갖는 붕괴파와 권파를 조파시켰다. 쇄파점에 가까워 질수록 붕괴파와 권파의 파형경사가 뚜렷하게 증가되었고 쇄파 후에는 감소되었다. 격렬한 권파시에는 파형경각가 보다 더 증가됨을 볼 수 있었다. 파군 중의 기본적인 주파수들은 파낭의 전파과정이나, 특히 격렬한 권파시에도 별 변동이 없었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.96-101
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• 2004

When the wind blows hard, most waves are breaking in sea. Breaking waves occur, exceeding limitation of wave steepness(wave height/wave length=l/7). Because a wave of single angular frequency couldn't generate the breaking phenomena at two dimensional ocean engineering basin, the breaking wave can be generated by the superposition of waves with various angular frequencies. We research how are the particle kinematics in the breaking wave and the magnitude of the breaking wave exciting force. We compare the force in a regular wave which has same specifications(wave height, period and length) as the breaking wave. Also the experimental results of wave exciting force and particle velocity are investigated by comparison on the analytic results using the potential theory.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.264-269
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• 2002

The wave profiles of directional breaking waves are investigated experimentally in a directional wave basin. The directional breaking waves are generated by component wave focusing both in direction and frequency based on constant wave steepness and constant wave amplitude spectrum models. the profile parameters of wave crest steepness and asymmetry are adapted to analyze the evolution of breaking ware characteristics in a view of focusing efficiency. The generated breaking waves are classified into the incipient, single and multi breaking waves.