• 교육시설
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• 제4권4호
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• pp.89-100
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• 1997

• 대한기계학회논문집
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• 제19권4호
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• pp.1102-1115
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• 1995

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purpose of the present study is to investigate the effect of the boundary layer thickness at the separation point on the reattachment length and to understand the structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separating and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. The study demonstrated that the reattachment length increases with increasing boundary layer thickness. It was also observed that the reverse flow velocity and turbulent kinetic energy decrease with an increase in the momentum thickness at the separation point. The measured velocity field suggests that the boundary layer thickness at the separation can affect definitely on the formation of corner eddy.

• 대한기계학회논문집
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• 제18권11호
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• pp.3039-3045
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• 1994

The k-$\varepsilon$ turbulence models by Launder et al.(1977, LPS) and Leschziner and Rodi(1981, LR) are modified to account for the secondary straining effect with having a generality in the present paper. The modified models are obtained by replacing the gradient Richardson number used to account for the secondary straining effect in the original models by a new parameter with a tensor-invariant correction form. These two modified models are used to predict the turbulent flow over a backward-facing step. In contrast to both standard and modified LR models, the modified LPS model is found to predict the reattachment point fairy well, as well as mean velocity, wall static pressure, turbulent kinetic energy and Reynolds shear stress in the recirculating region.

• 대한기계학회논문집
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• 제18권9호
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• pp.2463-2476
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• 1994

Local mean fluctuating velocity components were measured in the separating and reattaching axisymmetrc region of turbulent boundary layer over the wall of convex cylinders placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. Measurements were made with three different diameters of cylinders with four different diameters of cylinders with four different diameter of the obstructions. The range of Reynolds number based on step height was between 5,000 to 25,200. The study demonstrates that the reattachment length decreases with decreasing cylinder radius and is always shorter than that for the two-dimensional backward-facing step flow at the condition of the same step height. It was also observed that the turbulent kinetic energy in the recirculating region increases with an increases in the radius of convex curvature. The measured velocity field suggests that the transverse curvature can effect definitely the formation of corner eddy.

• 대한기계학회논문집B
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• 제36권9호
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• pp.923-930
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• 2012

입구유동 가진이 있는 층류 후향계단 유동에서 Pr수의 변화에 따른 열전달 특성변화를 조사하기 위하여 비정상 수치해석을 수행하였다. 입구는 가진주파수와 가진진폭의 변화에 따른 교란이 주어졌고, 온도함수의 물성치가 적용되었다. 열전달 변화에 대한 다양한 특징들이 열경계층 변화에 의해서 설명되었다. 물성치가 일정한 경우와 비교하였을 때, 물성치가 온도의 함수성이 있는 경우 Pr < 1인 조건에서 열전달은 감소하였고, 반대로 Pr > 1인 조건에서 열전달은 증가하였다. 또한 가진진폭이 증가함에 따라 계단 후류 바닥면에서 열전달도 증가하였다. 그렇지만 가진주파수 변화의 경우 St < 0.2인 조건에서 열전달이 크게 증가하는 특정주파수 영역이 존재하였다. 특히, 열전달의 증가는 재부착 길이의 rms값의 변동정도와 밀접한 관련이 있음을 보여주었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.117-124
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• 2000

As the reinforced earth wall is constructed with step by step backfill compaction method, the accumulative horizontal deformation is inevitable. It has been reported that about 80% of horizontal deformation is occurred during the construction stage of reinforced earth retaining wall. To reduce the horizontal deformation, an isolated-reinforced earth wall method(KOESWall system) was newly developed. In this system, the reinforced earth is constructed first with reinforcements and backfills only, and then facing blocks are installed after the horizontal displacement of reinforced earth is fully occurred. To evaluate the effect of a construction method and the performance of KOESWall system, two cases of full scale field performance was monitored during and after the construction stages.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 가을 학술발표회 논문집
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• pp.323-328
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• 2001

In the ordinary reinforced earth wall, which was constructed by incremental construction method, the horizontal deformation of the facing due to the compaction induced horizontal earth pressure was unavoidable. Thus the KOESWall system which are adopted the isolated construction method was developed by I&S Eng. Co., Ltd. in 1999. Due to its systematical feature, KOESWall system is able to minimizes the horizontal deformation of reinforced wall effectively and it can be used as temporary structures more economically without the lacing block. In this report, it is shown that the concept and case histories of KOESWall system as a retaining structures.

• 한국환경복원기술학회지
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• 제10권4호
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• pp.31-40
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• 2007

Recently, the scale in the field of reinforced soil retaining wall has been grown up like tiered reinforced soil retaining wall. However, there have been increasing number of collapse accidents and large scale of collapse. The design manual adopted in the construction fields have been inconsistent in tiered reinforced soil retaining wall. Therefore, this study performed finite element analysis on 90 cases and analyzed characteristic behavior of lower wall which was one of the effect factors on the stability of tiered reinforced soil retaining wall. The facing displacement of each walls and the behavior of the whole ground were interpreted by the numerical analysis depending on the lower offset distance by the upper wall as well as the upper offset distance by the surcharge load. The results showed that the behavior of tiered reinforced soil retaining wall was differed by condition of surcharge load and each offset distance was found to be important factor.

• 대한기계학회논문집
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• 제19권9호
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• pp.2328-2341
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• 1995

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purposes of the present study are to investigate the effect of the free stream turbulence intensity on the reattachment length and to understand the turbulence structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separated and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. As the free stream turbulence intensity increased, the reattachment length became shorter due to the enhanced mixing in the separated shear layer. It was also observed that the reverse flow velocity and turbulent kinetic energy increase with increasing free stream turbulence intensity. Spectral data and flow visualization showed that low-frequency motions occur in the separated flow behind a backward-facing step. These motions have a significant effect on the time-averaged turbulence data.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.805-812
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• 2003

The purpose of this study is to evaluate the behavior of a reinforced earth wall by modeling the properties of the interface between soil and reinforced elements as well as the non-linear stress-strain characteristics of soil. The effect of lateral earth pressures induced during construction is also included in the analyses. The interface element used to evaluate the relative movement of the interface between soil/reinforcement and soil/wall- facing has a zero thickness and essentially consists of normal and shear springs. The behavior of soil element is calculated based on the hyperbolic model. The computer program SSCOMPPC which includes the interface element, hyperbolic model and bi-linear model is applied in this study. From the analyses, it is showed that the locus of maximum tension were closed to the hi-linear failure line of theoretical analyses. The lateral displacement of SSCOMPPC is larger than that of the FLAC which adopts the elastic model. This means the analysis which is adopted the hyperbolic model and interface element induced more larger displacement.