• Title, Summary, Keyword: Incident wave

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A Study on the Characteristics of the Stem Wave in front of the Coastal Structure (해안구조물 전면의 Stem Wave특성에 관한 연구)

  • PARK HYO-BONG;YOON HAN-SAM;RYU CHEONG-RO
    • Journal of Ocean Engineering and Technology
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    • v.17 no.5
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    • pp.25-31
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    • 2003
  • Numerical experiments have been conducted using the nonlinear combined refraction-diffraction model, in order to analyze the generation characteristics of stem wave, which is formed by the interaction between vertical structure and the oblique incident waves. The results of stem wave are discussed through the stem wave height distribution along/normal vertical structure, under the wide range of incident wave conditions-wave heights, periods, depths, and angles. Under the same wave height and period, the larger the incident wave angle, the higher the stem wave heights. According to the results of wave height distribution, in front of vertical structure, the maximum of stern wave heights occurs in the location bordering the vertical wall. Furthermore, the most significant result is that stem waves occur under the incident angles between $0^{\circ}\;and\;30^{\circ}$, and the stem wave height ratio has the maximum value, which is approximately 1.85 times the incident wave height when the incident wave angle becomes $23^{\circ}$.

A Numerical Study on Pontoon Type Floating Breakwaters in Oblique Waves

  • Kim, Do-Young
    • International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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    • v.3 no.1
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    • pp.23-28
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    • 2000
  • A numerical investigation was made to examine characteristics of rectangular pontoon type floating breakwaters in oblique waves. Sway and heave wave exciting forces, roll moment acting on the floating breakwater and three motion reponses decrease as the incident wave angle increases for the most of the wave ranges. There exists a minimum wave transmission coefficient which is a function of wave frequency. In short wave range wave transmission coefficient increases as the incident wave angle increases. In long wave range, however, wave transmission coefficient decreases as the wave incident angle increases.

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Wave Reflection and Transmission Coefficients of Rubble Mound Breakwaters under Oblique Incident Waves (경사입사파랑중의 사석방파제에 의한 반사율과 투과율에 관한 연구)

  • 배기성;김도삼
    • Journal of Ocean Engineering and Technology
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    • v.15 no.1
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    • pp.31-35
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    • 2001
  • By applying the Boundary Integral Equation Method (BIEM) to obliquely incident for Rubble Mound Breakwater (RMB), wave reflection and transmission the coefficients are studied numerically. The validity of and the present BIEM is confirmed by comparing it with 1)numerical results of the eigenfunction expansion method of Dalrymple et al.(1991), and 2)numerical results of the BIEM of Kojima et al.(1988). Therefore, the characteristics of RMB for obliquely incident waves are investigated according to the variations of the wave period, equivalent linear nondimensional friction coefficient and direction of incident waves. It is revealed that the wave transformations of obliquely incident waves are different from those of normally incident waves.

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Experiments for Wave Velocity Distribution in front of Composite Structure by Incident Wave Angles (입사각에 따른 혼성식구조물 전면의 유속분포 실험)

  • Lee, Jong-In;Moon, Gang Il;Lim, Ho Seok
    • Journal of The Korean Society of Civil Engineers
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    • v.39 no.6
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    • pp.759-768
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    • 2019
  • The extended Tanimoto formula has been widely used to estimate the stability for the toe protection of the composite structure. However, the extended Tanimoto formula usually over-estimates armor weight when the incident waves approach the structure obliquely because the formula incident originally considered the normally incident wave cases. In this study, three-dimensional hydraulic model experiments were conducted to investigate the horizontal wave velocity under monochromatic and random wave conditions to investigate the prediction capability of the extended Tanimoto formula under the different incident wave angle conditions. The maximum horizontal wave velocity was measured near the toe for the normally incident wave condition. In the case of obliquely incident waves, the maximum horizontal wave velocity was measured under the stem wave generation condition. The results of the experiments showed a good agreement with the results by Takahashi et al.

Effect of Multi-directional Random Waves on Characteristics of 3-D Wave Field around Permeable Submerged Breakwaters (다방향 불규칙파가 투과성 잠제 주변의 3차원 파동장에 미치는 영향)

  • Hur, Dong-Soo;Lee, Woo-Dong
    • Journal of Ocean Engineering and Technology
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    • v.26 no.2
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    • pp.68-78
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    • 2012
  • This study proposes an improved 3-D model that includes a new non-reflected wave generation system for oblique incident and multi-directional random waves, which enables us to estimate the effect of the various wave-types on 3-D wave fields in a coastal area with permeable submerged breakwaters. Then, using the numerical results,the three-dimensional wave field characteristics around permeable submerged breakwaters are examined in cases of oblique incident and multi-directional random waves. Especially, the wave height, mean surface elevation and mean flow around the submerged breakwaters are discussed in relation to the variation of incident wave condition.

Characteristics of Incident Waves on Seaweed Farm Field Around Gumil-up Sea, Wando (완도 금일읍 주변해역 해조류 양식장에 내습하는 해양파랑 특성)

  • Jeon, Yong-Ho;Yoon, Han-Sam;Kim, Dong-Hwan;Kim, Heon-Tae
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.15 no.3
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    • pp.177-185
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    • 2012
  • Wave field measurements were made over a period of 18 days to study the spatial distribution of incident wave on seaweed tarm field around Gumil-up Sea, Wando, Korea. These measured data were compared with data from the Geomun-do ocean weather/wave observation buoy. A numerical simulation model that combined the offshore design wave with the seasonal normal incoming wave was used to study the incident wave distribution surrounding a seaweed farm. The results are summarized as follows. (1) On-site wave measurements showed that the major relationship between maximum and significant wave height was $H_{max}=1.6H_{1/3}$. (2) Offshore incident wave energy reaching the coast was greatly influenced by the wind direction. A north wind reduced the incident wave energy and a south wind increased it. (3) The calculated maximum wave height under the design wave boundany conditions was in the range of 4~5 m and the reduction in the incident wave height ratio ranged from approximately 38.1% to 47.6% at Gumil-up Sea. Under normal wave conditions, the maximum wave heights were 3.6~4.0 m in summer and 2.3~2.7 m in winter while the reduction in the incident wave height ratio was about 41.8% to 49.1%. (4) The sea state in the southern area of Gumil-up was the most affected by ocean waves, whereas the sea state in the northern area was very stable. The significant wave ratio in the south was about six times that in the north.

Numerical Analysis of Waves coming with Oblique Angle to Submerged Breakwater on the Porous Seabed (침투층 위의 잠제에 경사각을 가지고 입사하는 파랑의 수치해석)

  • Kim, Nam-Hyeong;Woo, Su-Min
    • Journal of Navigation and Port Research
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    • v.37 no.3
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    • pp.283-289
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    • 2013
  • Wave profiles coming with oblique angle to trapezoidal submerged breakwater on the porous seabed are computed numerically by using a boundary element method. The analysis method is based on the wave pressure function with the continuity in the analytical region including fluid and structure. When compared with the existing results on the oblique incident wave, the results of this study show good agreement. The fluctuation of wave profiles is increased in the rear of the submerged breakwater due to the increase of the transmission coefficient, as the incident angle increases. In addition, in the case of the wave profiles passing over the submerged breakwater on porous seabed, it is able to verify that the attenuation of wave height occurs more significantly due to the wave energy dissipation than that of passing over the submerged breakwater on the impermeable seabed. The results indicate that wave profile own high dependability regarding the change of oblique incident waves and porous seabed. Therefore, the results of this study are estimated to be applied as an accurate numerical analysis referring to oblique incident waves and porous seabed in real sea environment.

Variation of Incident Wave Angle in the Surf Zone Observed from Digital Videos (해안 비디오로부터 관측된 쇄파지역에서 입사각의 변화)

  • Yoo, Je-Seon;Shin, Dong-Min;Cho, Yong-Sik
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.2
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    • pp.154-163
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    • 2009
  • Incident wave angles are conventionally estimated by the directional spectrum analysis of wave data collected from in-situ sensors. The in-situ measurements are limited in monitoring incident wave angles in the wide surf zone, since the techniques are typically expensive, labor-intensive, and point-measuring. In this study, estimation of incident wave angles using wave crest features captured in digital video imagery is proposed to observe incident wave directions over the surf zone. Line signatures of wave crests having high image pixel intensities are extracted by moving an interrogation window to identify high intensity pixels in sequential video images. Wave angles are computed by taking the first derivative of the extracted crest signatures, i.e. local slope of the crest signatures in the two-dimensional physical plane. Compared to the wave angle estimates obtained by the directional spectrum analysis, video-based wave angle estimates show good agreements in general.

Characteristics of Wave Propagation by Water Level Conditions at Wando Sea Area: Numerical Modeling (완도 해역의 해수면 조건에 따른 파랑 변형 특성)

  • Jeon, Yong-Ho;Yoon, Han-Sam;Kim, Dong-Hwan;Kim, Won-Seok;Kim, Heon-Tae
    • Journal of Fisheries and Marine Sciences Education
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    • v.25 no.1
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    • pp.1-11
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    • 2013
  • The aim of this study was estimated the characteristics of the wave propagation by the water level conditions using a numerical modeling method at the Wando sea area. For three cases numerical simulation on the condition of incident and incoming of the deepwater design wave and the season normal wave, the spatial distribution of the incident wave at study area were investigated. And the calculated numerical modeling results were compared with measured field wave data. According to on-site wave data measured for 18 days, the range of the significant wave height and period were 0.10~1.14 m, 4.35~8.74 sec, respectively, and the maximum wave height were 0.15~1.66 m. From the results of numerical model for offshore design wave incident, the wave height attacked from Southern-East direction at this study area were over maximum 10.5 m because of rapidly change of water depth. Numerical modeling by three water level conditions of Approxmate Lowest Low Water Level(Approx. L.L.W), Mean Sea Level(M.S.L) and Approximate Highest High Water Level(Approx. H.H.W) were practiced. From the results for the case of Approx. H.W.L, variations of wave height at the back area of islands were about 1.6 m at maximum value for the case of deepwater design wave incoming. The significant wave heights of winter season were bigger than summer under normal wave condition, the incident wave height over 5.5 m decreased by shielding effect of islands. The change of maximum wave height at summer season were distinct than winter and was about 1.2 m and 0.8 m, respectively.

Detonation transmission with an abrupt change in area

  • Hsu, Yao-Chung;Chao, Yei-Chin;Chung, Kung-Ming
    • Advances in aircraft and spacecraft science
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    • v.5 no.5
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    • pp.533-550
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    • 2018
  • Detonation transmission between propane/oxygen (donor) and propane/air (acceptor) with an abrupt area change is experimentally studied. In the donor, there are two types of incident detonation waves: A self-sustained Chapman-Jouguet (CJ) detonation wave and an overdriven detonation wave that is a result of the difference in the initial donor pressure ratios. The piston work is used to characterize the strength of the incident detonation wave. For an incident CJ detonation wave, the re-initiation of a detonation wave in the acceptor depends on the initial pressure in the donor and the expansion ratio. The axisymmetric and non-axisymmetric soot patterns respectively correspond to direct detonation and detonation re-initiation. For an incident overdriven detonation wave, the re-initiation of a detonation wave in the acceptor strongly depends on the degree of overdrive.