• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1318-1322
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• 2006

보는 낙차공과 함께 하천에서 자주 시공되는 하천 구조물로 매년 태풍이나 홍수로 큰 피해를 나타내는 대표적인 시설물 중 하나이다. 구미의 경우에는 보 하류부에 정수지(stilling basin)등을 설치하여 에너지를 적절히 소산시켜 하류로 흘려보내는 공법을 사용하고 있으나 우리나라와 기후조건이 유사한 일본에서는 보하류부에 물받이 및 하상보호공을 설치하는 방법으로 보 설계를 하고 있어 하상보호공에 대한 설계개념에 차이가 있다. 현재 국내의 보 설계는 Bligh공식에 따라 물받이 및 하상보호공을 결정하였으나 지반의 침투영향을 고려하여 도출된 공식이므로 수리적 특성를 고려하지 못하는 한계성을 가지고 있다. 따라서 보에서 수리특성을 고려한 물받이 및 하상보호공 설계를 위한 수리실험을 통해 설계지침을 보완할 필요가 있다. 본 연구에서는 수리조건에 따른 하상보호공 길이를 제안하는데 목적이 있으며 이를 위해 난류유속강도를 주요영향 요소로 선정하여 도수 및 도수 후 구간에 대해 난류강도 변화를 분석하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.42-42
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• 2000

선형 터빈 익렬에 유입되는 자유흐름 난류 강도의 변화에 따른, 터빈 블레이드에서의 대류 열전달 현상에 대한 연구를 수행하였다. 익렬은 5개의 볼레이드를 선형으로 배치하여 구성하였으며, 현의 길이에 근거한 레이놀즈 수는 2.5${\times}$$10^5$, 3.5${\times}$$10^5$ 이다. 자유 흐름의 난류 강도는 익렬의 도입부에 설치된 격자의 형상에 따라 1.3%, 3.7%, 7.0%, 7.8%의 값을 나타내었다. 자유흐름의 난류강도는 정온 열선유속계로 측정하였으며, 블레이드 표면 온도 분포는 열전대를 사용하여 측정하고, 금속박판을 사용하여 균일한 열유속을 공급하였다.(중략)

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.367-371
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• 2005

본 논문에서는 수리실험을 통해 개수로의 바닥 조건에 따른 평균흐름 및 난류구조, 그리고 고유구조의 특성을 연구하였다. 레이저 도플러 유속계를 이용하여 2차원 순간속도를 측정하였다. 측정된 평균유속, 레이놀즈응력, 난류강도, 와점성계수, 혼합 길이 등의 난류량을 기존에 제시된 경험식과 비교하였으며 기존 연구 결과와 유사함을 확인하였다. 사분면 기법을 이용하여 개수로 흐름의 고유구조를 살펴본 결과, 분출 및 쓸기 현상의 발생 확률이 다른 상호작용에 비해 지배적임을 확인하였다. 고속 푸리에 변환을 통한 스펙트럼 분석을 통하여 에너지 폭포 현상 및 난류 와의 미시 및 거시 특성크기를 파악하였다.

• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.745-751
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• 2001

Fall velocities of sand particles in the turbulent flow are analyzed through measurements using PTV. PTV is believed to be the only instrument to measure the fall velocity in the turbulent flow, since it can trace the individual particle. The method is verified by comparison with existing formula for still-water case. The experimental results show that the fall velocity in the turbulent flow decreases compared with that in still water, and decreases by 40% as the turbulent intensity normalized by the friction velocity increases upto 1.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.92-98
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• 2003

The optimum design of Hanyang low speed wind tunnel has been performed to augment flow uniformity and to reduce turbulence intensity of wind tunnel test section have to be known for reliability of wind tunnel test. The non-uniformity and turbulence intensity of Hanyang low speed wind tunnel were measured with Pilot tube and X-type hot-wire probe at various wind speeds. As the results, the non-uniformity decreases as the wind speed increases. The non-uniformity is relatively high in the proximity of the diffuser. The turbulence intensity is a little higher than design requirement in the middle of the test section.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.930-934
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• 2007

본 논문은 수리실험을 통해 침수식생 개수로의 단면특성을 살펴보고자 하는 실험논문이다. 레이저 도플러 유속계를 이용하여 측벽으로부터의 거리에 따른 침수식생 개수로의 2차원 순간속도를 측정하였다. 측정된 유속자료를 이용하여, 평균유속, 레이놀즈응력, 난류강도를 살펴보았으며, 침수식생 개수로 흐름의 단면특성을 살펴보았다. 실험결과 침수식생 개수로는 기존의 일반적인 개수로흐름과는 다른 단면 흐름특성을 보이는 것을 확인하였다. 특히 최대유속 발생지점이 수로 중앙이 아닌 측벽 근처로 이동하였으며, 이차흐름의 영향으로 인하여 흐름방향 등유속선의 물결형태와 레이놀즈응력 및 난류강도의 최대값 발생위치 이동과 같은 현상이 발생하는 것을 확인하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.86-94
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• 1987

In order to examine the flow motion in a combustion chamber of a motored diesel engine, the variation of instantaneous are velocity at a fixed point in combustion chamber was measured by the constant temperature hot wire anemometer, varing engine speed, shroud shape and shroud position. The results are summerized as follows: 1. The variation of air velocity in a combustion chamber is closely related with the valve timing and piston velocity. 2. The air velocity in the cylinder at suction stroke is being increased and maximized at 60$^{\circ}$ ABDC in compression stroke and then decreased at the e.v.o. in expansion stroke. 3. The mean velocity using shroud valve was less than no shroud valve. However the turbulent intensity using shroud valve was larger than no shroud valve. 4. The turbulent intensity with 90$^{\circ}$shroud valve was larger than that of 120$^{\circ}$shroud valve, and 90$^{\circ}$shroud valve at 180$^{\circ}$shroud position had the largest turbulent intensity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.2
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• pp.40-40
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• 1987

In order to examine the flow motion in a combustion chamber of a motored diesel engine, the variation of instantaneous are velocity at a fixed point in combustion chamber was measured by the constant temperature hot wire anemometer, varing engine speed, shroud shape and shroud position. The results are summerized as follows: 1. The variation of air velocity in a combustion chamber is closely related with the valve timing and piston velocity. 2. The air velocity in the cylinder at suction stroke is being increased and maximized at 60° ABDC in compression stroke and then decreased at the e.v.o. in expansion stroke. 3. The mean velocity using shroud valve was less than no shroud valve. However the turbulent intensity using shroud valve was larger than no shroud valve. 4. The turbulent intensity with 90°shroud valve was larger than that of 120°shroud valve, and 90°shroud valve at 180°shroud position had the largest turbulent intensity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.645-650
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• 2016

In this study, we conducted a numerical simulation using Navier-Stokes Solver (HYMO-WASS-3D) in order to analyze wave attenuation under wave-current interaction found in existing hydraulic experiments. It showed that wave energy and wave height are reduced as the wave propagates in coexisting fields between waves and currents. And the wave attenuation became more serious as the velocity of current and thus turbulence intensity were increased at wave-current coexisting field. As well, the wave attenuation became more serious with lower wave height and shorter period when the wave propagates the same distance under interactions between waves and currents.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6B
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• pp.491-497
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• 2011

In this study, the flow characteristics around the cutter head, which makes the dredging soil suspended, were measured to evaluate the environmental affect of the dredging works. The PIV was used for measuring the flow characteristics around the cutter head for suction and non-suction cases. As the results, the mean velocity was decreased from the cutter head to outward. The mean velocity decreasing rate of the non-suction case was larger than that of the suction case, but the turbulence intensity decreasing rate of the non-suction case was smaller than that of the suction case because of the suction energy which makes the z-direction flow.