• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.26-34
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• 2009

Secondary flow losses can be as high as 30~50% of the total aerodynamic losses for a turbo-machinery blade or stator row. These are important part for improving a turbine efficiency. Therefore, many studies have been performed to decrease the secondary flow losses. The present study deals with the chamfered leading-edge at a generic wing-body junction to decrease the horseshoe vortex, one of factors to generate the secondary flow losses, and investigates the vortex generation and the characteristics of the horseshoe vortex with the chamfered height, and depth of the chamfer by using $FLUENT^{TM}$. It was found that the total pressure loss for the best case can be decreased about 1.55% compare to the baseline case.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.336-343
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• 2009

Secondary flow losses can be as high as 30~50% of the total aerodynamic losses generated in the cascade of a turbine. Therefore, these are important part for improving a turbine efficiency. As well, many studies have been performed to decrease the secondary flow losses. The present study deals with the leading edge fences on a wing-body to decrease a horseshoe vortex, one of the factors to generate the secondary flow losses, and investigates the characteristics of the generated horseshoe vortex as the shape factors, such as the installed height, and length of the fence. The study was investigated using $FLUENT^{TM}$. Total pressure loss coefficient was improved about 4.0 % at the best case than the baseline.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.56-64
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• 2013

The wind resistant capacity of bridges with a span of less than 200m is typically evaluated by Wind Resistant Design Manual for Highway Bridges in Japan. Also, the first vertical frequency plays an important role in the evaluation of their aerodynamic performance. An unexpected vortex-induced vibration of Nielsen arch bridge with span of 183m designed by this manual has been measured by monitoring system during typhoon. The amplitude of vibrations was about 2 times than the allowable vibration displacement. This paper presents the feature of vortex-induced vibration of this Nielsen arch bridge based on measured wind velocity, wind direction, and responses at midspan of main girder. From the result of FFT, the $1^{st}$ mode shape of the bridge is antisymmetric and the $2^{nd}$ is symmetric. Also, the dominant vibration of the bridge is the $2^{nd}$ vertical mode. According to these results, the $2^{nd}$ vertical vibration mode of this Nielsen arch bridge is prior to the first for the estimation of wind resistance capacity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.829-836
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• 2009

3-Dimensional flow which is represented by horseshoe vortex is generated as a type of secondary flow about the main flow. As well, it causes the flow loss. The present study deals with the leading edge fence shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge fence was optimized with the design variables of the installed height, length, width, and thickness of the fence as the design variables. Approximate optimization design method is used as the optimization. The study was investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. Total pressure coefficient of the optimized design case was decreased about 7.5 % compare to the baseline case.

• Journal of Energy Engineering
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• v.9 no.2
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• pp.89-94
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• 2000

양흡입 펌프 회전차 내부 유동특성을 수치적으로 고찰하였다. 수치계산은 설계점과 2개의 탈설계점에서 이루어졌으며, Patankar에 의해 제시된 SIMPLE 알고리즘을 이용하였다. 설계점에서는 양 회전차 채널 내부에서 대칭 형상을 갖는 이차유동 특성을 발견하였지만, 탈설계점에서는 비대칭 유동특성을 발견하였다. 수치해석 결과로는 유량감소에 따라 양흡입 펌프 회전차 채널내부의 이차유동 특성이 달라진다는 사실을 고찰하였다. 또한 양흡입 펌프 회전차 단면에는 모퉁이 와류가 존재함을 알 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.214-214
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• 2021

본 연구에서는 부유식방파제의 입사면과 전달면이 Slit으로 구성되어있어 유수실이 존재하는 투수성 부유식방파제에 대하여 2차원 자유도운동에 따른 발전가능성을 검토하였다. 입사파랑이 부유식방파제 유수실구간의 내부로 유입될 때 발생하는 강한 와류는 입사파랑의 주기와 파고가 증가할수록 궤적이 높고 길게 발생하게 된다. 이러한 원리를 이용하여 부유식방파제 유수실구간 입사면과 전달면에 각각 양방향으로 회전이 가능한 수차를 설치하고 와류 발생에 따른 2차 에너지 생성 가능성을 검토하였다. 실험결과, 입사파랑의 내습에 따라 수차는 시계방향과 반시계방향으로 회전하는 것을 확인할 수 있었으며, 상대적으로 주기가 긴 규칙파랑 실험조건(파고 0.1m, 주기 2.0sec)에서 약 0.5W 내외의 지속적인 전기에너지를 확보하는 것으로 검토되었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.185-191
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• 2008

The aerodynamic losses so attributed to the endwall - usually termed secondary flow losses or secondary losses - can be as high as 30$\sim$50% of the total aerodynamic losses in a blade or stator row. Inlet guide vanes, with lower total turning and higher convergence ratios, will have smaller secondary losses, amounting to as much as 20% of total loss for an inlet stator row. These are important part for improving a turbine efficiency. The present study deals with a leading edge chamfer groove on a wing-body to investigate the vortex generation and characteristics of a horseshoe vortex with the installed height, and depth of the groove. The current study is investigated with $FLUENT^{TM}$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.257-265
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• 2009

The present study deals with the leading edge shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge is optimized with design variables form the leading-edge shape. Approximate optimization design method is used for the optimization. The study is investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. As the result, total pressure coefficient of the optimized design case was decreased about 9.79% compare to the baseline case.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.6
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• pp.24-33
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• 2009

The present study deals with the optimization of the leading edge shape around a wing-body junction to minimize the strength of the horseshoe vortex, which is one of the main factor generating the secondary flow losses. For this purpose, approximate optimization method is used for the optimization. The study is performed by using $FLUENT^{TM}$ and $iSIGHT^{TM}$. The total pressure coefficient for the optimized model was decreased about 9.79% compared with the baseline model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.1-7
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• 2005

Incompressible Reynolds-averaged Navier-Stokes equations with $\varepsilon{-SST}$ turbulence model are adopted for the investigation of the flow fields between the square cylinder and the ground. When the grounds moves, the diminish of the shear layer intensity on the ground promotes the interaction between the lower and the upper separated shear layer of the cylinder. Hence vortex shedding occurs at the lower gap height than stationary ground. In the moving ground, the secondary shedding frequency disappears due to the absence of the separation bubble on the ground which exists in the stationary ground. In addition, the shedding frequency and aerodynamic coefficients in the moving ground become higher than those of the stationary ground.