• Proceedings of the KSME Conference
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• 2000.11b
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• pp.579-584
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• 2000

Algebraic Reynolds Stress (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the model's predictability. The applied numerical schemes are upwind scheme and skew-upwind scheme. The numerical results show good prediction in first order calculations (i.e., reattachment length, mean velocity, pressure), while they show slight deviations in second order (i.e., kinetic energy and turbulence intensity). By comparison with the previous results using $k-{\varepsilon}$ model, ARS model predicts better than the standard $k-{\varepsilon}$ model, however, predicts slightly worse than the $k-{\varepsilon}$ model including the streamline curvature modification. Additionally this study can reconfirm that skew-upwind scheme has approximately 25% improved predictability than upwind scheme.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.52-66
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• 1998

An experimental study on the flow characteristics was performed for a two-dimensional turbulent wall attaching offset jet at different oblique angles to a surface. The flow characteristics were investigated by using a split film probe with the modified Stock's calibration method. The jet mean velocity, turbulent intensity, wall static pressure coefficient profiles, and time-averaged reattachment point were measured at the Reynolds number Re (based on the nozzle width, D) ranging from 17700 to 53200, the offset ratio H/D from 2.5 to 10, and the inclined angle .alpha. from 0.deg. C to 40.deg. C. The Correlations between the maximum pressure position, minimum pressure position, and reattachment point and offset ratios, and inclined angles are presented.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.649-653
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• 2014

채널 내부에 장애물이 존재하는 유동 형태는 다양한 공학적 문제에서 나타나고 있으므로 여러 가지 형상 및 유동 조건에 따른 유동 특성 연구가 필요하다. 따라서 본 논문에서는 장애물의 형상을 일정한 크기의 원형 실린더로 설정하고 실린더는 위아래 채널 벽 중앙에 위치하도록 하여 2차원 채널 내에 원형 실린더가 존재하는 경우에 대하여 CFD연구를 수행하였다. 실린더와 위아래 채널 벽면과의 거리를 변화시켜 각각의 거리에 대해 유동 재부착 길이, 유동의 주기성, 항력계수 등의 유동 특성을 관찰하였다. 연구결과 각 간격[실린더벽면과 채널벽면간의 거리(G)/실린더지름(d)]이 0.5, 1, 2, 3, 5, 15에 따른 재 부착 지점(Reattachment Length)은 채널 벽면이 실린더로부터 멀어질수록 완전히 열린 유동장에서의 유동 재부착 지점에 수렴해간다는 것을 확인하였다. 즉 거리가 멀어질수록 벽면 영향이 줄어든다는 것을 확인하였다. 또한 각각의 경우에 대해 항력계수 값을 구하였고, 이를 완전히 열린 유동장에서의 항력계수 값과 비교해 보았다. 그 결과 벽면으로부터의 떨어진 거리가 5부터 벽면의 효과가 줄어들어 10이상이 되었을 때부터 그 영향이 아주 미미하다는 것을 확인하였다.

• The Journal of the Korean dental association
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• v.51 no.11
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• pp.604-609
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• 2013

Crown fractures are relatively common trauma to anterior teeth, and should be restored immediately in most cases. For those who suffer from unfortunate traumatic episode, the best treatment option should be minimally invasive approach. In the presence of fractured tooth fragment, reattachment procedure creates positive emotional response in the patient and simplifies the procedure and maintenance of the patient's original tooth anatomy and occlusion. Without fractured tooth fragment, next conservative option could be direct composite restoration which is based on minimal invasion concept. This article proposes simple and very conservative techniques that anyone can do in daily practice.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.550-559
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• 2004

Theoretical studies have been carried out to examine the influence of the grain geometry-dependent driving forces, which control the internal flow pattern of solid rockets. Numerical studies have been executed with the help of a two-dimensional code. This code solves standard k-omega turbulence equations using the coupled second order implicit unsteady formulation. It has been concluded that the grain port divergence angles have significant leverage on the formation of recirculation bubbles leading for pressure oscillations, flow separation and reattachment. In solid rockets flow reattachment will favour secondary ignition and that will add to the complexity of the starting transient prediction.

• Journal of the Korean Society of Visualization
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• v.6 no.1
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• pp.53-58
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• 2008

We carried out the experiments which controled the periodic jet in front of the fence to alter the fence wake. The experiments were performed in circulating water channel and the vertical fence was submerged in the boundary layer. The frequency, jet nozzle distance and speed of jet passing the slit were investigated. Each case divided into 20 phases and phase-averaged results were compared with uncontrolled fence flow. From the results, we found the specific frequency and nozzle distance which were good for reducing the reattachment length. In this case, the reattachment length was decreased 35% compared with the uncontrolled fence flow.

• Journal of Periodontal and Implant Science
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• v.7 no.1
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• pp.24.2-24.2
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• 1977

• Journal of Periodontal and Implant Science
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• v.10 no.1
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• pp.42-42
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• 1980

• Journal of Periodontal and Implant Science
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• v.9 no.1
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• pp.28.1-28.1
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• 1979

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.187-190
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• 2006

In the present study, effects of tree-stream turbulence and surface trip wire on the flow past a sphere at $Re\;=\;0.4\;{\times}\;10^5\;{\sim}\;2.8\;{\times}\;10^5$ are investigated through wind tunnel experiments. Various types of grids are installed upstream of the sphere in order to change the tree-stream turbulence intensity. In the case of surface trip wire, 0.5mm and 2mm trip wires are attached from $20^{\circ}\;{\sim}\;90^{\circ}$ at $10^{\circ}$ interval along the streamwise direction. To investigate the flow around a sphere, drag measurement using a load cell, surface-pressure measurement, surface visualization using oil-flow pattern and near-wall velocity measurement using an I-type hot-wire probe are conducted. In the variation of free-stream turbulence, the critical Reynolds number decreases and drag crisis occurs earlier with increasing turbulence intensity. With increasing Reynolds number, the laminar separation point moves downstream, but the reattachment point after laminar separation and the main separation point are fixed, resulting in constant drag coefficient at each free-stream turbulence intensity. At the supercritical regime, as Reynolds number is further increased, the separation bubble is regressed but the reattachment and the main separation points are fixed. In the case of surface trip wire directly disturbing the boundary layer flow, the critical Reynolds number decreases further with trip wire located more downstream. However, the drag coefficient after drag crisis remains constant irrespective of the trip location.