• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.10
• /
• pp.833-843
• /
• 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.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.631-636
• /
• 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
• /
• v.18 no.7
• /
• pp.1196-1202
• /
• 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
• /
• 2002.09a
• /
• pp.1-15
• /
• 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.

• Journal of Energy Engineering
• /
• v.11 no.4
• /
• pp.299-305
• /
• 2002

The present experimental and numerical investigations are performed on 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 devel-oped flow of water and that of 0.2％ CMC-water solution at a inner cylinder rotational speed of 0∼600 rpm, 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 decreased for turbulent flow regime.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.1
• /
• pp.71-79
• /
• 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
• /
• v.4 no.3
• /
• pp.201-213
• /
• 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.

• Journal of Navigation and Port Research
• /
• v.27 no.3
• /
• pp.253-258
• /
• 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.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.6
• /
• pp.822-833
• /
• 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.

• Korean Journal of Heritage: History & Science
• /
• v.42 no.1
• /
• pp.100-121
• /
• 2009

This study is subjected to those gardens of the Korean Folk Village 'Oeam-Ri' designed in 1920s. - transitional period of traditional gardens - and define socio-cultural change's influences and through documents on garden design, descendant's testimony and measured drawings, to understand that period's garden culture's characteristics according to garden design elements. This study applied following analysis methods and procedures to derive out characteristics of transitional garden culture. Analysis on socio-cultural characteristics in 1920s. Analysis on actual condition of transitional garden's design. In this point Outline of the Garden, Space formation, Garden designing elements are (1) water landscape, (2) plant, (3) structures, (4) paving, to derive out characteristics of the transitional garden. The results follow as below; First, during the transitional period 1920s, the economical development, fueled by opening nation's door to foreign countries and indication of collapse of statue systems together with idea of practical science and Enlightenment Thought, was element of changes in garden style. Second, Garden Designers of transitional gardens in 'Oeam-Ri' were limited to upper class of the society. They were wealthy enough to maintain their high social statue in rapidly changing society. As results, tendency of returning to nature developed gardens located in a site of scenic beauty and development of geographical features arranging techniques, and also showed copying foreign styles. Third, arrangement of garden and space composition, in most cases, composed of buildings and yards. Changes in water landscape features and garden spaces are centered to main-yard. Major changes of the garden spaces are water landscapes and plants that showing foreign influences. Fifth, scenic appearance techniques appears with dense garden space and emphasizing visual scenic view. Sixth, the characteristics of transitional garden design techniques are development of geographical feature arranging techniques, changes and mixture of the materials and garden types, emphasizing garden's decorative beauty, change of concept of yard within house into garden, changes from 'borrowing of landscapes' to 'selecting landscapes', changes of front garden from emptiness to fullness, changes of attitudes of enjoying gardens from 'staying calm in the garden' to 'moving or walking in the garden', changes to inner-oriented view, and changes from 'just watching and enjoying the nature' to 'enjoying specific objects'. This study is one of the efforts to restore the identity of Korean Traditional Garden by approaching and observing modern era which function as bridge between tradition and present day, and we observed transitional aspects of changes of traditional garden into modern garden. Hereafter, more studies will be needed to Modern Garden Design be recognized as part of Korean Garden Design History and these would be author's next assignment.