• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.5
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• pp.408-417
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• 2007

Recently, an artificial beach has been constructed compensating for loss of the natural one caused by the development of coastal area, as well as serving as a location for recreational activities such as sea bathing. It is well known that some structure should be constructed to protect an artificial beach from the outflow due to wave action of the reclaimed sand. In general, dike is utilized as the structure to protect an artificial beach. And, one of the factors which may need to be taken into consideration for stability of dike on seabed foundation is the ground water behavior behind dike. However, the interrelated phenomena of nonlinear wave and ground water response have relatively little attention although these interactions are important for stability of structure and sand suction to the artificial beach. In this paper, the numerical wave tank was developed to clarify nonlinear wave, dike and ground water dynamic interaction, which can simulate the difference of ground water and mean water level. Using the developed numerical wave tank, the present study investigates how variation of ground water level influences hydrodynamic characteristics in seabed around dike and numerically simulates the wave fields, pore flow patterns, pore water pressures and vorticities according to variation of ground water level. Numerical results explain well how hydrodynamic characteristics in seabed around dike is affected by the variation of ground water level.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1994.03a
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• pp.52-55
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• 1994

현대산업의 주요 에너지원인 석유는 매장량의 지역적 편중이 심하여 전량수입에 의존하는 우리나라의 경우 정부의 에너지 수급정책이 국제 정세 흐름에 크게 영향을 받음. 과거 우리는 1,2차 석유파동을 통하여 안정적 에너지 공급의 위협을 받아 국가 경제 및 국민생활에 막대한 혼란을 경험한 바 있음. (중략)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.260-265
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• 1994

A new set of elliptic wave equations describing the deformations of irregular waves on a large-scale current field in water of irregular depth is given, and using finite difference scheme an efficient numerical method is also presented. The elliptic equations are solved in a similar way to Initial value problem. This method is extensively used for the calculation of wave spectral transformation. and computation results agree very well with experimental data (Hiraishi, 1991). Finally numerical examples are presented concerning the interactions between waves and currents over a mildly sloping beach and also over a mound.

• KOREAN POULTRY JOURNAL
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• v.40 no.1 s.459
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• pp.112-116
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• 2008

국제 곡물가격이 연일 급등세를 보이며 세계 곡물시장이 요동치고 있다. 10년 전인 1996년 엘리뇨 현상에 따른 지구촌의 기상이변으로 곡물파동을 겪은 바 있다. 10년 이상 지난 지금까지 일부 최빈국을 제외한 대다수의 국가가 곡물파동의 아픔을 잊고 행복한 시간을 보내지 않았나 하는 생각이 든다. 세계 경제가 미국을 중심으로 민주주의와 자본주의 경제가 주축을 이루며 경제적인 부, 즉 돈만 있으면 언제든지 쌀독에 쌀을 가득 채울 수 있었기 때문에 먹거리의 중요성에 대하여 소홀하며 살아온 것 같다. 그러나, 이제 더 이상 돈만 있다고 원하는 만큼 먹거리를 확보하기란 쉽지 않는 시대가 도래하고 있다. 작년 하반기부터 국제곡물가격은 가히 폭등이라고 할 만큼 큰 폭으로 상승하였는데, 문제는 과거처럼 단순히 기상악화에 따른 작황부진과는 차원이 다르다는 것이다. 지구촌 기상이변에 더불어 세계 경제성장에 따른 소비구조 변화와 이에 따른 수급불균형이 더욱 심화되고 있다는 것이다. 이에 금년도 세계 곡물산업 현황과 가격변동 흐름을 짚어보고 향후 사료원료를 중심으로 곡물수급 전망을 조명하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.457-467
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• 2004

Wave Transmission analysis is one of methods for power transmission and reflection coefficients in coupled infinite structures. This paper focuses the wave transmission analysis of point coupled structures among semi-infinite beams and infinite thin plates considering all kinds of waves. It is supposed that the junction through the beams and plates is an identical spot and no point of contact exist except the spot. The boundary conditions are applied at the spot for continuities of 6 DOF displacements and 6 DOF force equilibriums, and then wave fields are obtained in the coupled structures. Since wave components in plate field are simplified using asymptotic expressions of Henkel functions, the displacements and forces at the plate junction can be simply expressed with magnitudes of the wave components. The wave fields according to incident waves gives the power transmission coefficients in beam/plate point coupled structures. For both coupled structures with a beam vertically and obliquely joined to a plate, power transmission analysis is performed and the analysis results are compared and examined.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.12
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• pp.999-1006
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• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.897-908
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• 2008

황강에는 1989년 합천다목적댐과 본댐 하류 6.5km 지점에 조정지댐이 건설되었는데 조정지댐의 건설 목적은 본댐에서 피크 발전에 의해 방류되는 유량을 하류로 조절방류하기 위한것이다. 황강은 두댐의 건설후 하천폭, 하상재료, 식생 및 하천구간내 사주의 형성 등 많은 하천 지형학적 변화가 있었다. 이러한 변화는 댐 건설후 흐름 및 유사이송의 변화에 기인한다. 2002년 합천댐 저수지 퇴사량 조사에 의하면 합천댐은 연간 약 600천$m^3$의 유사를 차단한 것으로 파악되었다. 조정지댐은 연최대피크 방류량을 654.7$m^3/s$에서 126.3$m^3/s$로 감소시켰는데 이는 댐건설전의 19.3%에 해당하는 양이다. 댐건설로 인한 하류 하천의 지형적인 변화를 파악하기 위하여 합천조정지댐 하류로부터 낙동강 합류점까지 45 km에 대하여 조사하였다. 1982, 1993 및 2004년의 항공사진을 분석한 결과 비식생하도폭(non-vegetated active channel width)은 평균 152m 감소되었는데 이는 1982년의 약 53%에 해당한다. 비식생하도의 면적 역시 평균 6.6$km^2$가 감소하였다. 평균 중앙하상재료(D50)의 크기는 1983년 1.07mm에서 2003년 5.72mm로 증가한 반면 평균 하상구배는 1983년 0.000943에서 2003년 0.000847로 감소하였다. 총 하상 세굴깊이는 조정지댐 하류 20km 구간에서 평균 약 2.6m였다. 1차원 유사모형인 GSTAR-1D를 이용하여 예측된 최심하상고는 2013-2015년 사이 (댐건설후 약 25년 후)에 안정된 상태에 도달하는 것으로 나타났다. 합천 조정지댐이 본 댐에서의 피크 방류량을 상당히 감소시키고 있지만 홍수기에 조정지댐 수문의 급격하고 주기적인 개폐로 인하여 하류에 흐름의 펄스를 발생시키고 있다. 이러한 펄스가 하류 하천 지형변화에 미치는 영향을 파악하기 위하여 유사모형과 해석적인 방법을 개발 적용하여 구한 값과 비교 검토 하였다. 결과에 따르면, 일 흐름의 펄스(daily pulse)와 홍수피크(flood peak)는 각각의 평균값이 흐를 때와 비교하여 하천지형변화에 훨씬 큰 영향을 미치는 것으로 나타났다. 일 흐름 펄스와 홍수피크는 각각의 평균값의 21%와 15%의 토사 이송량 (tons/day) 증가를 보여주었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.324-338
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• 2015

Analytical solutions for interaction between seabed and waves such as progressive wave or partial standing wave with arbitrary reflection ratio or standing wave have been developed by many researchers including Lee et al.(2014; 2015a; 2015b; 2015c; 2015d) and Yamamoto et al.(1978). They handled the pore-water pressure as oscillating pore-water pressure and residual pore-water pressure separately and discussed the seabed response on each pore-water pressure. However, based on field observations and laboratory experiments, the oscillating and residual pore-water pressures in the seabed do occur not separately but together at the same time. Therefore, the pore-water pressure should be investigated from a total pore-water pressure point of view. Thus, in this paper, the wave-induced seabed response including liquefaction depth was discussed among oscillating, residual, and total pore-water pressures' point of view according to the variation of wave, seabed, and flow conditions. From the results, in the field of flow with the same direction of progressive wave, the following seabed response has been identified; with increase of flow velocity, the dimensionless oscillating pore-water pressure increases, but the dimensionless residual pore-water pressure decreases, and consequently the dimensionless total pore-water pressure and the dimensionless liquefaction depth decrease.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.345-357
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• 2011

Recently, as part of diversifying energy sources and earth environmental issues, technology development of new renewable energy using wave energy is actively promoted and commercialized around Europe and Japan etc. In particular, OWC(Oscillating Water Column) wave power generation system using air flow induced by vertical movement of the water surface by waves in an air-chamber within caisson is known as the most efficient wave energy absorption device and therefore, is one of the wave power generation apparatus the closest to commercialization. This study examines air flow velocity, which operates turbine(Wells turbine) directly in oscillating water column type wave power generation structure from two-and three-dimensional numerical experiments and discusses optimal shape of oscillating water column type wave power generation structure by estimating the maximum flow rate of air according to change in shape. The three-dimensional numerical wave flume was applied in interpretation for this study which is the model for the immiscible two-phase flow based on the Navier-Stokes Equation. From this, it turned out that size of optimal shape appears differently according to the incident wave period and air flow is maximized at the period where minimum reflection ratio occurs.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.5 s.149
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• pp.597-603
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• 2006

The estimations of distributed and joint-excited input power for Power Flow Analysis are accomplished in this paper. Using Fourier transform, the displacements of infinite structures are derived, and the input power of distributed excitation can be estimated. The obtained results compare the real input power with the estimation of input power. When the exciting force acts on the joint of coupled structures, it is estimating the power that is transferred to each structure. Appling this input power, the results of energy density and intensity of Power Flow Analysis can be compared with the classical solutions.