• Title/Summary/Keyword: The Wave Environment

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An Experimental Investigation on the Hydrodynamic Characteristics of Submerged Artificial Seabed System in Regular Waves (중층계류식 인공해저시스템의 파랑중 운동특성에 관한 실험적 연구)

  • Yoon Sang-Joon;Yang Chan-Kyu;Kim Hyeon-Ju;Kim Heon-Tae
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.5 no.2
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    • pp.19-27
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    • 2002
  • This paper deals with the experimental investigation on the hydrodynamic behavior of the submerged artificial seabed system in regular waves. This system can function as a basis of seaweed forest which will cultivate coastal fishing ground and enhance coastal productivity. The experiment was conducted with the submerged rectangular plates of different length and depth in 2-D wave flume of KRISO/KORDI. The wave exciting forces, mooring line tension and 2-D motion response are measured and analyzed to figure out the design strategy.

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A Study on the Abnormal and Fault Reproduction Method for Smart Monitoring of Thrust Bearing in Wave Power Generation System (파력발전 시스템 쓰러스트 베어링의 스마트 모니터링을 위한 이상 및 고장 운용 재현 방법에 관한 연구)

  • Oh, Jaewon;Min, Cheonhong;Sung, Kiyoung;Kang, Kwangu;Noh, Hyon-Jeong;Kim, Taewook;Cho, Sugil
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.5
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    • pp.835-842
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    • 2020
  • This paper considers a method of reproducing abnormal and fault operation for smart monitoring of thrust bearing used in wave power generation system. In order to develop smart monitoring technology, abnormal and failure data of actual equipment are required. However, it is impossible to artificially break down the actual equipment in operation due to safety and cost. To tackle this problem, a test bed that can secure data through reproduction of a faulty operating environment should be developed. Therefore, in this study, test bed that can reproduce each situation was developed and the operation result was analysis after identifying the situation to be reproduced through the failure factor analysis of the thrust bearing.

Analysis of Wave Load and Mooring System for Ocean Monitoring Facilities - About an estimation method for horizontal force of circular pile in sand - (해상관측시설을 위한 파랑하중과 계류계 해석 -모래중에 뭍힌 원형파일의 수평력 추정방법을 중심으로-)

  • Yoon Gil Su;Kim Yong Jig;Kim Dong Joon;Kang Sin Young
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.1 no.1
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    • pp.102-111
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    • 1998
  • Ocean monitoring facilities are divided into two types, fixed type and floating type. This paper deals with wane load calculation and mooring system for a floating monitoring facility. Wave load and drift forces are calculated for an example case of floating monitoring buoy To enlarge holding power of anchor, circular pile model test was performed. A program for horizontal force of circular pile in sand was made and the calculated result showed fairy good agreement with the result of model test. It is expected that this method will provide good estimation for the holding power of the prototype of circular pile anchor which is relied upon SCUBA activity for installation.

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Field observation of sediment suspension in the surf zone (쇄파대의 저질부유에 관한 현지관측)

  • Shin, Seung-Ho;Kuriyama, Yoshiaki
    • Journal of Navigation and Port Research
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    • v.27 no.4
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    • pp.455-463
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    • 2003
  • Time series of suspended sediment concentration, surface elevation and velocity were measured and analysed to investigate the role of waves and the predominance of infra-gravity wave component for sediment suspension phenomena in the surf zone. For the investigation in detail, we adopted the cross spectral analysis method between suspended sediment concentration and the characteristic values of wave, and ensemble average analysis method about long-period wave component, which is dominant to sediment suspension in the measurement point. The obtained results are summarized as follows: 1)The relationship between suspended sediment concentration and the characteristic values of wave is stronger for the long-period standing wave components(about 60s and 30s where the nodal point of the first mode and the anti-nodal point of the second mode are located at the measurement point, respectively) than the long wave components(about 100s), which have the most energetic power, 2) and also, it is cleared that suspended sediment concentration is increased in the case of the phase, the velocity components of the first mode long-period standing wave(60sec) were accelerated toward on-shore direction, that is, the water surface in offshore side is higher than on-shore side.

Hydraulic Model Experimental Study on the Rope Kink Phenomena and Mooring Block Behavior under Wave Conditions at a Seaweed Farm (연승 수하식 양식시설의 파랑 중 해조류 꼬임 현상 및 계류용 블록 이동에 관한 수리모형 실험적 연구)

  • Kim, Heon-Tae;Choi, Jin-Hyu;Yoon, Han-Sam
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.20 no.1
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    • pp.11-17
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    • 2014
  • In this study, a hydraulic model experiment under wave conditions was carried out to investigate the gap/distance between two near-unit farm lines that affects the rope kink and shape variation of a seaweed farm during mooring block movement. As a result, rope kink occurred during the low wave height condition as the gap/distance between the two near-unit farm lines decreased. The seaweed farm maintained a stable shape in the higher wave height conditions as the gap/distance between the two near-unit farm lines increased. This result indicates that rope kink is sensitively affected by the gap/distance between the two near-unit farm lines. A tendency to increase the critical wave height was observed when mooring block movement occurred, and as the mooring block weight and wave period increased. From the experimental results in which incident wave conditions and the mooring block weight changed, as the front side mooring block weight increased from 3.0 to 8.0 tons, the seaweed farm was stable, and rear side mooring block movement hardly occurred. The observed tension of the seaside mooring line was a maximum at about 3.0 ton/m.

A Study on the Evaluation of Cargo Securing Safety for Car ferry Ships Using Wave Height Information (해상 파고 정보를 활용한 카페리 선박의 고박안전성 평가에 관한 연구)

  • Yu, Yong-Ung
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.4
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    • pp.457-464
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    • 2021
  • Cargo securing safety, which is one factor for the safe operation of car ferry ships, has been applied since 2015 and evaluated by comparing the hull motion and securing load capacity generated by waves. To ensure the safe operation of the 3700 ton class car ferry, it is important to analyze the hull acceleration motion based on the sea wave information of the navigation area to determine the cargo securing load that can prevent the movement of cargo. In this study, the meteorological information of three wave buoys installed in Busan and Jeju area was analyzed for the past 5 years. In addition, the hull acceleration was measured in actual sea conditions and compared to that of numerical simulations. Under the condition of a significant wave height of 2.5 m from Feb to Mar, except typhoon seasons, the lateral acceleration was observed to be 1.5 m/s2 in real ship measuring and 1.8 m/s2 in numerical calculation. It was analyzed to be less than 40% under general weather conditions compared to the high wave warning using an approximate formula for estimating the hull motion by wave height. The cargo securing safety proposed in this study will be widely used based on the actual measuring acceleration with the sea wave height.

Study on Hydrodynamic Forces Acting on a Very Large Container Vessel at Lower Depths in Both Still Water and Waves (정수중 및 파랑중 저수심에서의 초대형 컨테이너선에 작용하는 유체력 특성에 관한 연구)

  • Lee, Sangmin
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.23 no.6
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    • pp.613-619
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    • 2017
  • Recently, the size of container ships has been progressively increasing, and much attention is required for safe navigation in shallow areas such as coastal waters and ports due to increases in draft. It is necessary to understand the characteristics of ship motion not only in still waters but also with waves. Especially in shallow regions, squat due to the vertical movement of the ship can be an important evaluation factor for the safe navigation, and wave drift force acting in the horizontal direction can have a great influence on the maneuverability of a ship. In this study, a numerical simulation using computational fluid dynamics has been performed for the wave exciting force acting in the vertical direction and the wave drift force acting in the horizontal direction for a very large container vessel sailing in shallow zone. As a result, it was found that total resistance in still waters greatly increased in shallow water. Wave drift force was shown to decrease given longer wavelengths regardless of water depth. It was observed that the wave exciting force in shallow water was considerably larger than at other water depths. As wave height against the central part of the ship lowered, the aft side rose.

Instability of Plunging Breaking Wave Impact on Inclined Cylinder (경사진 실린더에 작용하는 플런징 쇄파 충격력의 불안정성 고찰)

  • Hong, Key-Yong;Shin, Seung-Ho
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.10 no.4
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    • pp.187-192
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    • 2007
  • Impact on cylindrical surface caused by plunging breaking waves is investigated experimentally. The breaking waves are generated in a wave flume by decreasing the wave maker frequencies linearly and focusing the generated wave components at one specific location. The breaking wave packets are based on constant wave steepness spectrum. Three inclination angles of cylinder are applied to examine the effect of contact angle between cylinder and front surface of breaking waves. Also, the effect of cylinder diameter on pressure distribution and its peak value is investigated by adopting three cylinders with different diameters. The longitudinal location of cylinder is slightly moved in eight different points to find out a probable maximum value of impact pressure. The pressures and total force on cylinder surface are measured by piezo-electric pressure sensors and 3-components load cell with 30kHz sampling rate. The variation of peak impact pressures and forces is analyzed in terms of cylinder diameter, inclination angle and location. Also, the pressure distribution on cylindrical surface is examined. The cylinder location and surface position are more important parameters that govern the magnitude and shape of peak pressures, while the cylinder diameter and inclined angle are relatively insignificant. In a certain conditions, the impact phenomenon becomes very unstable which results in a large variation of measured valves in repeated runs.

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Wave propagation of FG-CNTRC plates in thermal environment using the high-order shear deformation plate theory

  • Hao-Xuan Ding;Hai-Bo Liu;Gui-Lin She;Fei Wu
    • Computers and Concrete
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    • v.32 no.2
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    • pp.207-215
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    • 2023
  • This paper investigates wave propagation in functionally graded carbon nano-reinforced composite (FG-CNTRC) plates under the influence of temperature based on Reddy' plate model. The material properties of Carbon Nanotubes (CNTs) are size-dependent, and the volume fraction of CNTs varies only along the thickness direction of the plate for different CNTs reinforcement modes. In addition, the material properties of CNTs can vary for different temperature parameters. By solving the eigenvalue problem, analytical dispersion relations can be derived for CNTRC plates. The partial differential equations for the system are derived from Lagrange's principle and higher order shear deformation theory is used to obtain the wave equations for the CNTRC plate. Numerical analyses show that the wave propagation properties in the CNTRC plate are related to the volume fraction parameters of the CNTRC plate and the distribution pattern of the CNTs in the polymer matrix. The effects of different volume fractions of CNTs and the distribution pattern of carbon nanotubes along the cross section (UD-O-X plate) are discussed in detail.

Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave

  • Byun, Sun-Joon;Kwak, Dong-Kurl
    • Journal of Electrochemical Science and Technology
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    • v.10 no.2
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    • pp.104-114
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    • 2019
  • Energy is an essential driving force for modern society. In particular, electricity has become the standard source of power for almost every aspect of life. Electric power runs lights, televisions, cell phones, laptops, etc. However, it has become apparent that the current methods of producing this most valuable commodity combustion of fossil fuels are of limited supply and has become detrimental for the Earth's environment. It is also self-evident, given the fact that these resources are non-renewable, that these sources of energy will eventually run out. One of the most promising alternatives to the burning of fossil fuel in the production of electric power is the proton exchange membrane (PEM) fuel cell. The PEM fuel cell is environmentally friendly and achieves much higher efficiencies than a combustion engine. Water management is an important issue of PEM fuel cell operation. Water is the product of the electrochemical reactions inside fuel cell. If liquid water accumulation becomes excessive in a fuel cell, water columns will clog the gas flow channel. This condition is referred to as flooding. A number of researchers have examined the water removal methods in order to improve the performance. In this paper, a new water removal method that investigates the use of vibro-acoustic methods is presented. Piezo-actuators are devices to generate the flexural wave and are attached at end of a cathode bipolar plate. The "flexural wave" is used to impart energy to resting droplets and thus cause movement of the droplets in the direction of the traveling wave.