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수직축 풍력 터빈 블레이드의 최적화 설계 및 Vortex 구조 분석
나지성(Jisung Na),고승철(Seungchul Ko),선상규(Sanggyu Sun),방유석(Yusuk Bang),이준상(Joon Sang Lee) 한국가시화정보학회 2015 한국가시화정보학회지 Vol.13 No.1
Sensitivity studies of blade angle and twisted angle are numerically investigated to optimize the Savonius blade. As blade angle increases, the contact area between blade and wind decreases, showing the suppression of the vortex generation near blade. Compared to the blade angle of 0 degree, the blade angle of 20 degree shows about 2.6% increment of power efficiency. Based on the blade angle of 20 degree, sensitivity studies of the twisted angle are performed. The result indicates that the adjustment of the twisted angle causes the torque of blade to increase. Optimized blade can suppress the formation of the vortex structure in rear region. Also, wind flows without disturbance of vortex when passing through the optimized blade. The 1kw vertical wind turbine system with optimized blade can generate 4442.2kWh per year and have 53% capacity factor.
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나지성(J.S Na),진경(Emilia K. Jin),이준상(Joon Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Nowadays, many unusual weather phenomena around the world are attributed to global warming effect. And, many researchers feel the need to study on the GCMs (General Circulation Model). We investigate the global surface temperature by using the CCSM3 (Community climate System) provided by NCAR, and compare the simulation results with the measured temperatures. Moreover, we analyze the surface temperature around the Korean peninsula at the 21st century. We use the SRES (Special Report on Emissions Scenarios) A1B which is one of the imaginary emission scenarios in this research. We find that the fluctuation of the surface temperature around the Korean peninsula is related with a rapid climate change considerably. Hence, we analyze the surface temperature around the Korean peninsula by comparing with the validated simulation results. We see the results that climate change around the Korean peninsula will be occurred rapidly at the 21st century.
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나지성(Jisung Na),고승철(Seungchul Ko),이준상(Joon Sang Lee) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.3
In this study, we investigate the wake characteristics in laminar inflow and two different turbulent inflow cases. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. We perform the quantitative analysis of velocity deficit and turbulent intensity in laminar inflow case and turbulent inflow case with different turbulent intensity. In turbulent inflow, unsteady strong wake recovery which is highly fluctuated in time. Normalized power in turbulent inflow case is also highly fluctuated with unsteady wake recovery, while that in laminar inflow has quasi steady characteristic in power generation.
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나지성(Jisung Na),고승철(Seungchul Ko),이준상(Joon Sang Lee) 한국가시화정보학회 2016 한국가시화정보학회지 Vol.14 No.3
In this study, we investigate the wake characteristics in two cases which are laminar inflow and turbulent inflow. To solve the flow with wind turbines and its wake, we use large eddy simulation (LES) technique with actuator line method (ALM) and turbulent inflow of Turbsim. Turbulent inflow which contains the characteristic of the stable atmospheric boundary layer is used. We perform the quantitative analysis of velocity deficit and turbulence intensity in two cases. Time series of velocity deficit at the first, the second column in two cases are compared to observe the performance of wind turbine. The performance in the first column in laminar inflow is overestimated compared to that in turbulent inflow. And we observe that wake in the case with turbulent inflow drive to the span-wise direction and wake recovery in turbulent inflow is more effective. In quadrant analysis of Reynolds stress, the ejection and the sweep motion in turbulent inflow case are bigger than those in laminar inflow case.
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해양-빙붕 상호작용을 고려한 남극 테라노바 만에서 수괴 형성과 순환의 수치 시뮬레이션
김태균,진경,나지성,이춘기,이원상,문재홍 한국해양과학기술원 2023 Ocean and Polar Research Vol.44 No.4
The interaction between ocean and ice shelf is a critical physical process in relation to water mass transformations and ice shelf melting/freezing at the ocean-ice interface. However, it remains challenging to thoroughly understand the process due to a lack of observational data with respect to ice shelf cavities. This is the first study to simulate the variability and circulation of water mass both overlying the continental shelf and underneath an ice shelf and an ice tongue in the Terra Nova Bay (TNB), East Antarctica. To explore the properties of water mass and circulation patterns in the TNB and the corresponding effects on sub ice shelf basal melting, we explicitly incorporate the dynamic-thermodynamic processes acting on the ice shelf in the Regional Ocean Modeling System. The simulated water mass formation and circulation in the TNB region agree well with previous studies. The model results show that the TNB circulation is dominated by the geostrophic currents driven by lateral density gradients induced by the releasing of brine or freshwater at the polynya of the TNB. Meanwhile, the circulation dynamics in the cavity under the Nansen Ice shelf (NIS) are different from those in the TNB. The gravity-driven bottom current induced by High Salinity Shelf Water (HSSW) formed at the TNB polynya flows towards the grounding line, and the buoyance-driven flow associated with glacial meltwater generated by the HSSW emerges from the cavity along the ice base. Both current systems compose the thermohaline overturning circulation in the NIS cavity. This study estimates the NIS basal melting rate to be 0.98 m/a, which is comparable to the previously observed melt rate. However, the melting rate shows a significant variation in space and time.
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