• Title, Summary, Keyword: Wave maker

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On the Wave Source Identification of an Wave Maker Problem

  • JANG TAEK-SOO
    • Journal of Ocean Engineering and Technology
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    • v.17 no.5
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    • pp.19-24
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    • 2003
  • The question of wave source identification in a wave maker problem is the primary objective of the this paper. With the observed wave elevation, the existence of the wave maker velocity is discussed with the help of the mathematical theory of inverse problems. Utilizing the property of the Strum-Liouville system and compactness, the uniqueness and the ill-posedness(in the sense of stability) for the identification are proved.

A Comparative Study on Numerical and Wave-maker Generated Waves (조파기 단면현상 변화에 따른 파형 해석)

  • LEE JONG-HYUN;JANG TAEK-SOO;KWON SUN-HONG;HWANG SUNG-HYUN
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.263-267
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    • 2004
  • This paper presents a comparative study on numerical and wave-maker generated waves. The wave-makers employed to carry out the experiments have mathematical forms. The linear and quadratic models were tested. When it comes numerical analysis, the authors used the FLUENT which is widely used commercial code. Only two dimensional cases were considered. The experiments were done in a small wave flume. The waves were generated for various frequencies to examine the characteristics of the water waves. The comparison of the numerical and wave-maker generated waves were made.

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A Parametric Study of the Wave-Generation Performance of a Piston-Type Wave Maker (피스톤 타입 조파기의 형상 매개변수에 대한 조파성능 연구)

  • Kwon, Do-Soo;Kim, Sung-Jae;Koo, Weoncheol
    • Journal of Ocean Engineering and Technology
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    • v.33 no.6
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    • pp.504-509
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    • 2019
  • The wave-generation performance of a piston-type wave maker was analyzed using the numerical wave tank technique, and the numerical results were compared with theoretical solutions. A two-dimensional frequency domain analysis was conducted based on the Rankine panel method. Various parameters were used to examine the wave-generation performance, such as the width and gap of the wave board. The effects of the thickness of the wave board and of the gap from the bottom of the tank were evaluated. The difference in the amplitude of the generated wave between the analytical solution and the numerical result was examined, and its causes were addressed due to the gap flow between the bottom of the tank and the wave board. This parametric analysis can be utilized to design an optimum wave make parametric analysis to design an optimum wave maker that can generate waves with amplitudes that can be predicted accurately.

Adaptive Re-reflecting Wave Control In Plunger Type Wave Maker System: Experiments In Two Dimensional Wave Basin

  • Park, Gun-Il;Kim, Ki-Jung;Park, Jae-Woong;Lee, Jin-Ho
    • Journal of Ship and Ocean Technology
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    • v.7 no.1
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    • pp.13-18
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    • 2003
  • The control performances for active re-reflecting wave control suggested in the previous paper have been verified in cases of regular and irregular waves in a real two dimensional wave basin. For regular waves, the control performances are investigated in terms of reflection coefficients, expected amplitudes of propagating waves and wave absorbing capabilities after cessation of wave generation, compared with those of no-control cases. For irregular waves similar verification procedures were adopted. Though there are certain constraints due to the geometrical non-linearity of wave maker and certain nonlinear characteristics due to the near field and gravity waves these experiments show that the control logic could be useful in realizing re-reflecting wave control in conditions of real wave basin.

Adaptive Re-reflecting Wave Control in Plunger Type Wave Maker System: Theory

  • Park, Jae-Woong;Lee, Jin-Ho;Park, Gun-Il;Kim, Ki-Jung
    • Journal of Ship and Ocean Technology
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    • v.6 no.4
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    • pp.13-18
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    • 2002
  • Active control has been partly applied to suppress the re-reflecting waves in wave basin with plunger-type wave maker to obtain desirable waves. This limitation comes from the non-confirmable theoretical background to the control algorithm. This paper proposes control logic to overcome this drawback, based on the impulse response function for propagating waves between control input and the wave height. The performances have been verified as reasonable in practical application by comparing with the propagating wave components in numerical wave basin, using wave decomposition method. Moreover, the control logic can also give useful wave-absorbing performance after cessation of wave generation.

Internal Wave-Maker using Momentum Source Term of RANS Equation Model (RANS 방정식의 운동량 원천항을 이용한 내부조파)

  • Choi, Jun-Woo;Ko, Kwang-Oh;Yoon, Sung-Bum
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.2
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    • pp.182-190
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    • 2009
  • For RANS equation model using VOF scheme Lin and Liu (1999) developed internal wave-maker method to generate target wave trains by using designed mass source functions of the continuity equation. By using this method studies on various numerical wave experiments has been achieved without the problem caused by wave reflection due to an external wave-maker. In this study, the wave-maker method to generate target wave trains by using a momentum source function was proposed. The computational results obtained by applying the mass and momentum source functions into FLUENT were compared with each other. To see its applicability, the hydraulic experiment of Luth et al. (1994) were numerically simulated and their measurements are compared with the computations, and the vertical variations of computed results were shown and investigated.

Spatial Modulation of Nonlinear Waves and Their Kinematics using a Numerical Wave Tank (수치 파동 수조를 이용한 비선형파의 파형변화와 속도분포 해석)

  • Koo, Weon-Cheol;Choi, Ka-Ram
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.12-16
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    • 2009
  • In this study, the wave profiles and kinematics of highly nonlinear waves at various water depths were calculated using a 2D fully nonlinear Numerical Wave Tank (NWT). The NWT was developed based on the Boundary Element Method (BEM) with the potential theory and the mixed Eulerian-Lagrangian (MEL) time marching scheme by 4th-order Runge-Kutta time integration. The spatial variation of intermediate-depth waves along the direction of wave propagation was caused by the unintended generation of 2nd-order free waves, which were originally investigated both theoretically and experimentally by Goda (1998). These free waves were induced by the mismatch between the linear motion of wave maker and nonlinear displacement of water particles adjacent to the maker. When the 2nd-order wave maker motion was applied, the spatial modulation of the waves caused by the free waves was not observed. The respective magnitudes of the nonlinear wave components for various water depths were compared. It was found that the high-order wave components greatly increase as the water depth decreases. The wave kinematics at various locations were calculated and compared with the linear and the Stokes 2nd-order theories.

Numerical Simulation of Directional Spreading Characteristics in a Snake Type Wave Generator considering Side Wall Reflection

  • Lee, Jin-Ho;Hirayama, Tsugukiyo
    • Journal of Ship and Ocean Technology
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    • v.4 no.1
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    • pp.28-36
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    • 2000
  • Numerical simulation based on the superposition of ring waves generated by the linear periodic source distributions for the plunger type wave maker was accomplished. The characteristics of directional spreading function were investigated. Mirror images are also introduced to consider reflections of side-wall together with the reflection coefficient to account for the imperfect reflection from the real side wall in the long experimental towing tank. Unexpected spurious waves, resulting from the combined effect of finite breadth of segmented wave maker, wavelength and main wave maker, wavelength and main wave propagating direction, were observed in the line source method and also in the analysis of the directivity. The influence of spurious waves to the directional spreading function was also investigated.

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Performance Analysis of Floating Wave Energy Converter by Using CFD (CFD를 이용한 부양식 파력발전 장치의 성능해석)

  • CHOI, Yong-Seok;LIM, Tae-Woo;KIM, You-Taek
    • Journal of Fisheries and Marine Sciences Education
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    • v.27 no.5
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    • pp.1303-1309
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    • 2015
  • The behavior and flow characteristics of the floating wave energy converter were analyzed by using CFD in this study. The average significant wave height was confirmed as 0.5~2.0m from the Korean coastal sea area. This study was carried out by selecting a range of 1.0~1.6m in the wave height to simulate the operations of realistic wave energy converter system. The principle of a piston wave maker was applied in order to produce periodic wave. The behavior of the wave energy converter and the state of the wave overtopping according to the generated periodic wave were confirmed through the unsteady three-dimensional flow analysis. It was found that the wave overtopping rate according to the generated periodic wave was in range of the 11.6~30.0 kg/s.

Investigation of Characteristics of Waves Generated in Two-Dimensional Wave Channel (2차원 조파수조에서의 파 생성 특성 조사)

  • Ahn, Jae-Youl;Choi, Jung-Kyu;Kim, Hyoung-Tae
    • Journal of Ocean Engineering and Technology
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    • v.27 no.4
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    • pp.68-75
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    • 2013
  • This paper investigates the characteristics of waves generated by a flap-type wave maker in a two-dimensional wave channel. Measurements are carried out for various water depths, wave heights, periods, and lengths capacitance-type wave height gages. The experimental results are shown to satisfy the dispersion relation of the linear wave theory. For waves with a small height and long period, the wave profiles agree well with those of the linear wave theory. However, as the wave height and period become higher and shorter, respectively, it is shown that the wave profiles measured in the present experiments are different from the linear wave profiles, and the measured wave heights are smaller than the target wave heights, which may be due to the non-linearity of the waves. As the wave progresses toward the channel end, the wave height gradually decreases. This reduction in the wave height along the wave channel is explained by the wave energy dissipation due to the friction of the side walls of the channel. The performance of the wave absorber in the channel is found to be acceptable from the results of the wave reflection tests.