• 설비공학논문집
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• 제14권10호
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• pp.833-843
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• 2002

The present experimental and numerical investigations are performed for the characteristics of transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure losses and skin- friction coefficients have been measured for the fully developed flow of water and glycerine-water solution (44%) with the inner cylinder rotating at speed of 0∼600 nm, respectively. The transitional flow has been examined by the measurement of pressure losses to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients. The occurrence of transition has been checked by the gradient changes of pressure losses and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.631-636
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• 2000

The experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ration of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure drops and skin-friction coefficients have been measured for the fully developed flow of water and that of glycerine-water solution (44%) at a inner cylinder rotational speed of $0{\sim}600$ rpm, respectively. The transitional flow have been examined by the measurement of pressure drops and the visualization of flow field, to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients and to understand the flow instability mechanism. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. The occurrence of transition has been checked by the gradient changes of pressure drops and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, is gradually declined for turbulent flow regime. Consequently, the critical (axial-flow) Reynolds number decreases as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the excitation of taylor vortices.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1196-1202
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• 2004

To evaluate the unsteady motion in laterally berthing maneuver, it is necessary to estimate clearly the magnitudes and properties of hydrodynamic forces acting on ship hull in shallow water. A numerical simulation has been performed to investigate quantitatively the hydrodynamic force according to water depth for Wigley model using the CFD (Computational Fluid Dynamics) technique. By comparing the computational results with the experimental ones, the validity of the CFD method was verified. The numerical solutions successfully captured some features of transient flow around the berthing ship. The transitional lateral force in a state ranging from the rest to the uniform motion is modeled by using the concept of circulation.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2002년도 정기총회 및 제4회 특별심포지움
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• pp.1-15
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• 2002

In the present paper, the marine reflection seismic survey, the survey using Chirp sonar, the detail topographic survey by narrow multi-beam sounding machine, the sea bottom geological condition survey by side-scan sonar, the sea bottom sampling by core sampler and the positioning by DGPS as the geophysical survey in shallow and transitional region are introduced by placing emphasis on hardware configuration.

• 에너지공학
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• 제11권4호
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• pp.299-305
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• 2002

본 연구에서 실험과 수치해석 검증은 지름비 0.52인 동심환형관내에서 안쪽축이 회전하고 바깥쪽축이 고정된 유동장의 유동특성을 수행하였다. 압력손실과 마찰계수는 안쪽축이 0~600 rpm 회전시 물과 0.2% CMC 수용액을 완전히 발달된 유동장에서 측정하였다. 천이유동은 표면마찰계수(C$_{f}$ )에 대하여 로스비수(Ro)와 레이놀즈수(Re)관계를 나타내기 위하여 압력손실 측정에 의해 확인하였다. 천이발생은 레이놀즈수에 대하여 압력손실과 마찰계수의 구배변화에 의해 조사하였다. 회전으로 인한 마찰계수의 증가율은 천이영역에서 대하여 갑자기 감소함에 반하여 층류영역에서 균일하며, 난류영역에서는 점차적으로 감소함을 알 수 있었다.

• 한국농공학회논문집
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• 제56권1호
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• pp.71-79
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• 2014

In this study, an experiment with large-scale model was performed according to raising the embankment in order to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The pore water pressure, earth pressure, settlement and failure pattern by a rapid drawdown and overtopping were compared and analyzed. The pore water pressure and earth pressure at spillway transitional zone by overtopping increased a rapidly with the expansion of seepage erosion, but the crest showed a smally change due to effect of the inclined core type. And it is considered an useful data that can accurately estimate the possibility of failure of the reservoirs. A settlement at overtopping decreased a rapidly due to failure of crest. The relative settlement difference due to change of the water level at the upstream and downstream slope cause increase largely crack of crest. The behavior of failure by overtopping was gradually enlarged towards reservoirs crest from the bottom of the spillway transition zone, the inclined core after the raising the embankment was influenced significantly to prevent the seepage erosion.

• Ocean Systems Engineering
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• 제4권3호
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• pp.201-213
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• 2014

Wave run-up is an important issue in offshore engineering, which is tightly related to the loads on the marine structures. In this study, a series of physical experiments have been performed to investigate the wave run-up around a vertical cylinder in transitional water depth. The wave run-ups of regular waves, irregular waves and focused waves have been presented and the characteristics in frequency domain have been investigated with the FFT and wavelet transform methods. This study focuses on the nonlinear features of the wave run-up and the interaction between the wave run-up and the cylinder. The results show that the nonlinear interaction between the waves and the structures might result wave run-up components of higher frequencies. The wave run-ups of the moderate irregular waves exhibit 2nd order nonlinear characteristics. For the focused waves, the incident waves are of strong nonlinearity and the wavelet coherence analysis reveals that the wave run-up at focal moment contains combined contributions from almost all the frequency components of the focused wave sequence and the contributions of frequency components up to 4th order harmonic levels are recommended to be included.

• 한국항해항만학회지
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• 제27권3호
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• pp.253-258
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• 2003

To evaluate the unsteady motion in laterally berthing maneuver, it is necessary to grasp very clearly the magnitude and properties of the hydrodynamic forces acting on ship hull in shallow water. In this study, numerical calculation was made to investigate quantitatively the hydrodynamic force according to the water depth for Wigley model using the CFD (Computational Fluid Dynamics) technique. Comparing the computational results to the experimental ones, the validity of the CFD method was verified. The numerical solutions evaluated the hydrodynamic force with good accuracy, and then captured the features of the flow field around the ship in detail. The transitional lateral force in a state ranging from rest to uniform motion is modeled by using the concept of the circulation.

• 대한기계학회논문집B
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• 제24권6호
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• pp.822-833
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• 2000

This experimental study concerns the characteristics of a transitional flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one rotating. The pressure drops and skin-friction coefficients have been measured for the fully developed flow of water and that of glycerine-water solution (44%) at a inner cylinder rotational speed of $0{\sim}600$ rpm, respectively. The transitional flow has been examined by the measurement of pressure drops and the visualization of flow field, to reveal the relation of the Reynolds and Rossby numbers with the skin-friction coefficients and to understand the flow instability mechanism. The present results show that the skin-friction coefficients have the significant relation with the Rossby numbers, only for laminar regime. The occurrence of transition has been checked by the gradient changes of pressure drops and skin-friction coefficients with respect to the Reynolds numbers. The increasing rate of skin-friction coefficient due to the rotation is uniform for laminar flow regime, whereas it is suddenly reduced for transitional flow regime and, then, it is gradually declined for turbulent flow regime. Consequently, the critical (axial-flow) Reynolds number decreases as the rotational speed increases. Thus, the rotation of inner cylinder promotes the early occurrence of transition due to the excitation of taylor vortices.

• 헤리티지:역사와 과학
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• 제42권1호
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• pp.100-121
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• 2009

본 연구는 1920년대 외암리 민속마을을 사례로 정원의 전환기적 양상에 대해 정원요소를 중심으로 다루었다. 이 시기에는 사회 경제 문화적 변화에 따른 종래의 전통적 정원양식과 다른 양식의 정원구성요소가 나타날 것이라는 가설하에 정원구성요소로 수경, 식물, 구조물, 포장 등의 변화를 중심으로 고찰하였다. 연구결과는 다음과 같이 요약될 수 있다. 전환기적 시기인 1920년대는 외부적으로는 외세의 영향과 안으로 실학사상, 개화사상과 더불어 신분제도상의 붕괴조짐이 정원설계요소 변화의 요인으로 작용하였다. 외세의 영향으로 외래양식의 도입과 외래수종의 사용이 증가하였으며, 내부적 신분제도상의 변화는 정원양식의 탈규범화를 촉진하여 상위지향적 형태 및 재료의 사용과 공간기능의 변용을 초래하였다. 전환기적 정원의 특성이 나타나는 정원 조영자는 신분제도상의 붕괴에 불구하고 경제력을 바탕으로 새로운 사회변화에 지배계급으로 위치를 공고히 한 상류계층에 국한되어 있으며, 식민치하의 사회 혼란상으로부터의 도피적 행태나 선진문물을 선구적으로 받아들이는 행위를 통하여 정원의 변화에 직 간접적으로 영향을 미치게 된다. 이의 결과로, 자연에 심산 유곡에 위치한 정원의 입지와 지형처리기술을 발달시켰으며, 외래의 양식을 차용하고 사랑마당 정원을 변모시키는 정원조성행태를 보이게 된다. 정원의 배치 및 공간구성에서 전환기적 양상이 두드러진 유형은 건물과 마당(내원)으로 공간구획의 유형이 가장 높은 빈도를 보이고 있는데, 이는 전환기적 정원설계요소의 출현이 빈번한 유형으로 수경관의 형태와 정원공간의 변화는 사랑 마당을 중심으로 변화하고 있으며, 외래적인 요소의 영향이 지대한 수경관과 수목, 점경물 등의 도입이 주요한 공간변화를 일으킨 요인으로 볼 수 있다. 전환기적 정원요소로 수경관에서는 계류를 중심으로 한 부정형지의 회유식 연못이 주를 이루며, 식물은 전통수종이 주를 이루는 가운데 외래수종과 토피아리형 수목인 상록침엽수, 관목류의 출현이 두드러지며 건조물은 외래형식이 가미되고 점경물은 형태와 배치기법 등에 변화가 나타나며 원로가 자주 사용되기도 한다. 전환기적 정원조성기법의 특징은 적극적인 지형처리기법과 정원소유를 위한 영역성의 증대, 정원재료 및 형태의 변화와 양식의 혼재, 정원의 장식미 추구, 정원 내 의식공간의 퇴조, 동선처리 기법의 변화, 차경에서 선경으로의 취경기법의 변화, 사랑마당 공간 변화, 정적인 정원감상기법에서 동적으로의 변화 및 은유에서 직유로 정원표현기법이 달라지고 있다. 또한 정원을 중심으로 한 내부지향적 시각구조로의 변화를 들 수 있다. 본 연구는 한국전통정원의 정체성을 찾고자 하는 일환으로 전통과 현대의 교량 역할을 하는 근대시기에 대해 접근해 본 것으로 시기적 양상은 전통정원에서 근대정원으로 전이되는 전환기적 양상을 중심으로 고찰한 것이다. 향후, 한국조경사의 한 부분으로 근대조경의 시기가 인식되기 위해서는 보다 많은 사례의 다각적인 접근을 통한 연구가 지속되어야 할 것이며, 이는 추후 과제로 삼는다.