• 한국수자원학회논문집
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• 제31권3호
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• pp.223-234
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• 1998

파랑제어 및 표사제어라고 하는 해안·항만구조물의 원래의 기능 이외에 해양·해안환경의 유지·개선의 기능까지도 갖춘 투과성잠제에 의한 비선형파랑변형을 해석하였다. 해석법으로서 Stokes 3차파에 기초한 섭동전개법과 경계요소법을 병용하는 주파수영역해석법을 처음으로 투과성잠제의 파랑변형에 적용하였다. 투과층내의 유체운동의 저항에는 Dupuit-Forchheimer의 저항식을 적용하며, Lorentz의 등가일원리에 기초하여 얻어지는 등가선형마찰계수의 산정식을 공간적분만의 형태로 나타내었다. 본 이론의 검증을 위하여 수리모형실험을 실시하였으며, 얻어진 수리모형실험결과는 수치해석결과와 잘 일치하므로 그의 타당성이 검증되었고, 본 해석결과가 Stokes 2차파에 기초한 결과보다도 더 정확성을 가진다는 것을 확인할 수 있었다.

• 한국항만학회지
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• 제8권1호
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• pp.41-47
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• 1994

The present paper discusses the nonlinear wave deformation due to a submerged coastal structure. Theory is based on the frequency-domain method using the third order perturbation and boundary integral method. Theoretical development to the second order perturbation and boundary integral method. Theoretical development to the second order Stokes wave for a bottom-seated submerged breakwater to the sea floor is newly expanded to the third order for a submerged coastal structure shown in Figure 1. Validity is demonstrated by comparing numerical results with the experimental ones of a rectangular air chamber structure, which has the same dimensions as that of this study. Nonlinear waves become larger and larger with wave propagation above the crown of the structure, and are transmitted to the onshore side of the structure. These characteristics are shown greatly as the increment of Ursell number on the structure. The total water profile depends largely on the phase lag among the first, second and third order component waves.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1511-1521
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• 2002

High-speed moist air or steam flow has long been of important subject in engineering and industrial applications. Of many complicated gas dynamics problems involved in moist air flows, the most challenging task is to understand the nonequilibrium condensation phenomenon when the moist air rapidly expands through a flow device. Many theoretical and experimental studies using supersonic wind tunnels have devoted to the understanding of the nonequilibrium condensation flow physics so far. However, the nonequilibrium condensation can be also generated in the subsonic flows induced by the unsteady expansion waves in shock tube. The major flow physics of the nonequilibrium condensation in this application may be different from those obtained in the supersonic wind tunnels. In the current study, the nonequilibrium condensation phenomenon caused by the unsteady expansion waves in a shock tube is analyzed by using the two-dimensional, unsteady, Navier-Stokes equations, which are fully coupled with a droplet growth equation. The third-order TVD MUSCL scheme is applied to solve the governing equation systems. The computational results are compared with the previous experimental data. The time-dependent behavior of nonequilibrium condensation of moist air in shock tube is investigated in details. The results show that the major characteristics of the nonequilibrium condensation phenomenon in shock tube are very different from those in the supersonic wind tunnels.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.299-304
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• 2001

The current study describes experimental and computational work on the passive control of the steady and unsteady condensation shock waves, which are generated in a transonic nozzle. The bleed slots are installed on the contoured wall of the transonic nozzle in order to control the magnitude of the condensation shock wave and its oscillations. For computations, a droplet growth equation is incorporated into the two-dimensional Navier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order tractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. An experiment using an indraft transonic wind tunnel is made to validate the computational results. The current computations represented well the experimental flows. From both the experimental and computational results it is found that the magnitude of the condensation shock wave in the bleed slotted nozzle is significantly reduced, compared with no passive control of solid wall. The oscillations of the condensation shock wave are successfully suppressed by a bleed slot system.

• 대한기계학회논문집B
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• 제26권7호
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• pp.997-1004
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• 2002

The current study describes experimental and computational works on the passive control of the steady and unsteady condensation shock waves, which are generated in a transonic nozzle. The bleed slots are installed on the contoured wall of the transonic nozzle in order 10 control the magnitude of the condensation shock wave and its oscillations. For computations, a droplet growth equation is copuled with two-dimensional Navier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. An experiment using an indrafi transonic wind tunnel is made to validate the computational results. The current computations represented well the experimental flows. From both the experimental and computational results it is found that the magnitude of the condensation shock wave in the bleed slotted nozzle is signi ficantly reduced, compared with no passive control of solid wall. The oscillations of the condensation shock wave are successfully suppressed by a bleed slot system.

• 대한토목학회논문집
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• 제29권3B호
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• pp.289-301
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• 2009

본 연구에서는 Navier-Stokes방정식과 자유수면추적을 위해 도입한 VOF함수의 이류방정식에 기초하고 있는 CADMAS-SURF(CDIT, 2001)에 Fenton(1972)의 3차근사고립파이론에 의한 조파이론을 새롭게 도입한 수치파동수로로부터 직립호안상에서 지진해일(고립파)의 처오름 및 작용파력을 해석한다. 기존의 연구결과와 대비하여 본 수치해석결과의 적용성을 논의하며, 최소자승법에 기초하여 직립호안상에서 최대처오름과 최대파력을 합리적으로 추정할 수 있는 회귀식을 제안한다. 또한, 육상구조물에 작용하는 지진해일(tsunami wave)의 파력산정에 CADMAS-SURF(CDIT, 2001)의 적용을 시도한다. 육상에서 지진해일의 수위변동, 유속 및 파력변동의 특성으로부터 육상구조물에 미치는 지진해일의 직접적인 영향을 추론할 수 있을것이다.