• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.191-200
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• 2011

Levee failure cause the huge amount of damage to human and property. Overflow and erosion of levee are primary cause of a break in a levee but the analysis of breach pattern and impact is partially inadequate. The flow characteristics of meandering rivers are very important in field of river hydraulics that should be studied in practical viewpoints relating to river levee. In meandering the secondary flow that rotary direction is changed reciprocally occurs in three dimension is known. In this study flow characteristics of local river are considered and of meandering channels are analyzed using CCHE2D and FLOW3D. The stability and accuracy of models are examined comparing the measuring and analyzed data for the experimental channel and natural river(Namgang). Consequently, the flow characteristics in a meandering river are suggested precisely and it is essential that river levees having meandering river should be analyzed.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.414-418
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• 2005

A finite element model is developed for the numerical simulation of bed elevation change in a curved channel. The SU/PG (Streamline-Upwind/Petrov-Galerkin) method is used to solve 2D shallow water equations and the BG (Bubnov-Galerkin) method is used for the Exner equation. For the time derivative terms, the Crank-Nicolson scheme is used. The developed model is a decoupled model in a sense that the bed elevation does not change simultaneously with the flow during the computational time step. The total load formula with is used for the sediment transport model. The slip conditions are described along the lateral boundaries. The effects of gravity force due to geometry change and the secondary flows in a curved channel are considered in the model. For the verification, the model is applied to two laboratory experiments. The first is $140^{\circ}$ bended channel data at Delft Hydraulics Laboratory and the second is $140^{\circ}$ bended channel data at Laboratory of Fluid Mechanics of the Delft University of Technology. The finite element grid is constructed with linear quadrilateral elements. It is found that the computed results are in good agreement with measured data, showing a point bar at the inner bank and a pool at the outer bank.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.107-109
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• 2003

We propose a wall distance free one-equation turbulence model. The model is organized in an extremely simple form. Only a few model constants were introduced into the model. The model is numerically tough and easy-of-use. The model also demonstrated the ability to simulate the laminar to turbulent flow transition. The model has been applied to the channel flow, the plane jet, the backward facing step flow, the flat plate boundary layer, as well as the flow around the 2D airfoil at large angles of attack, which obtained satisfactory results.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.213-216
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• 2002

In this paper, flow patterns around two vertical cylinders were investigated numerically and experimentally Flow patterns between cylinders are very complex and interative. Changing gaps between cylinders the flow patterns are measured and numerically studied at a fixed comming velocity. The experiment has beeen conducted in circulating water channel with PIV system and manometer, and numerical analysis has been made by F.D.M. and multi block method. The results can be applied in the understanding and design of multiple pile array structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1B
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• pp.35-45
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• 2009

In this study, a laboratory experiment has been performed on a S-curved channel with two curved sections. In the experiments, effects of 3-D velocity structures on mixing characteristics of tracer material were investigated. As a result, it was clearly noticed that the primary flow travels taking the shortest course of the meandering channel and has a very ununiform distribution at the bends. The secondary cell which was developing at the first bend disappears at the crossover, and then, at the next bend, secondary cell is re-developing in the opposite direction. The experimental results show that mixing of tracer is significantly affected by the combined action of ununiform primary flow and secondary cell. The ununiform primary flow separates the tracer cloud in the longitudinal direction, and the secondary cell further separates the retarding tracer cloud mainly in the transverse direction. As a result, these complex flow structures cause separation and spreading of tracer cloud both in the longitudinal and in the transverse directions. The measured dimensionless transverse dispersion coefficients calculated using 2-D routing procedure ranges 0.012-0.875, and is generally proportional to width to depth ratio (W/h). The predicted values calculated by the theoretical equation overestimate slightly the measured transverse dispersion coefficients.

• Progress in Superconductivity and Cryogenics
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• v.7 no.2
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• pp.1-6
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• 2005

The Particle Image Velocimetry (PIV) technique can be used to obtain a whole-field view of thermal counterflow velocity profile in He II. Using commercially available microspheres, we have been able to visualize the normal fluid velocity in He II thermal counterflow; however, the measured velocities are less than predicted from the two fluid model. None the less, the PIV is a useful tool for observing the counterflow field in He II flow, particularly where the flow is complex as occurs through channel constrictions or around bluff objects. The present paper shows recent results using PIV to observe He II counterflow. Two cases are discussed: 1D channel flow and turbulent flow around a circular cylinder.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.128-133
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• 2002

The heat transfer characteristics of a turbulent flow in a ribbed two-dimensional channel have been investigated numerically. The fully elliptic governing equations, coupled with a four-equation turbulence model, $\kappa-\omega-\bar{t^2}-\epsilon_t$, are solved by a finite volume method of SIMPLE type. Calculations have been carried out for three rib cross-sections : square, triangular, and semicircular, with various rib pitches and Reynolds numbers. The procedure appears to be satisfactory as the results for the square rib compare favorably with available experimental data and earlier calculation. The optimal rib pitch that yields the maximum heat transfer has been identified. It is also found that the square rib is most effective in enhancing the heat transfer. The semicircular rib, on the other hand, incurs the least amount of pressure drop but the improvement in heat transfer is substantially lower.

• Solar Energy
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• v.17 no.3
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• pp.35-41
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• 1997

An experimental study was carried out in a vertical channel with square heat source by visualization equipment with laser apparatus. The image processing system consists of one commercial image board slit into a personal computer and 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system which adopted two-frame grey-level cross correlation algorithm. Heat source was uniform heat flux(5W). The obtained results show various flow patterns such as the kinetic energy distribution and the turbulent kinetic energy distribution.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.290-290
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• 2017

본 연구는 안정하도 설계를 위해 대상구간으로 원주천 16 km, 20개 횡단면에 대하여 SCAD(Stable Channel Analysis Design)를 이용한 안정하폭 평가를 실시하였다. 안정하폭은 하폭이 증가와 감소로 20%의 허용범위를 적용하였다. 안정하폭의 설계와 물리서식처의 개선을 위해 저수로 폭의 최적 설계를 제시하기 위해 유전자알고리즘을 이용하였다. 물리서식처 개선은 원주천의 하천환경조사와 어류의 군집특성을 이용하여 수중생태계를 대표 할 수 있는 복원 목표어종으로 참갈겨니를 선택하였다. 참갈겨니의 서식적합지수 (HSI, Habitat Suitability Index)를 사용한 서식 적합도 분석은 River2D 모형을 이용하였다. 그에 따라 안정하도 설계와 물리서식처의 개선을 위한 각 단면의 최적 저수로 폭을 제시하였다. 개선된 하천구조에 대한 물리적 교란개선 평가를 실시하였다. 대산구간을 40개 구간으로 분할하여 각 구간의 물리적 교란개선 평가를 수행하여 안정하도 설계와 물리서식처 개선을 위한 하천구조의 개선에 따른 물리적 교란 양상을 평가 분석하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.39-44
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• 2008

In this paper, heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated and the diameter and depth of dimple was 16mm and 4mm, respectively. Two channel heights of about 0.6 and 1.2 time of the dimple diameter, two dimple configuration were tested. The Reynolds numbers based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With same dimple arrangement, the heat transfer coefficients and the thermal performance factor were higher for the lower channel height. As the distance between dimples became smaller, the overall heat transfer coefficient and the thermal performance factor were increased.