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고승철(Seungchul Ko),나지성(Jisung Na),이준상(Joon Sang Lee) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.1
In this study, we conduct a numerical experiment of the single 5MW NREL wind turbine and compare the performance of various vortex core identification for the wake behind the wind turbine. In the kinetic analysis of wind turbine, 20% velocity deficit at 200 s is observed, showing wake which contains tip vortex near blade tip and rotor vortex at the center of the wind turbine. Time series of velocity and turbulent intensity show numerical simulation converge to a quasi-steady state near 200 s. In the comparison between methods for vortex identification, λ2-method has good performance in terms of tip vortex, rotor vortex, vortex during its cascade process compared to vorticity magnitude criteria, Δ-method. We conclude that λ2-method is suitable for vortex identification method for wake visualization.
고승철(Seungchul Ko),나지성(Jisung Na),이준상(Joon Sang Lee) 한국가시화정보학회 2017 한국가시화정보학회지 Vol.15 No.3
In this study, we investigate the flow characteristics of lift-type disk which behaves the up-down motion using the large eddy simulation (LES) and immersed boundary method (IBM). Also, we perform the noise analysis using pressure field at 1.35 m distance and reveal the cause of noise to observe the vortical structure analysis of flow result. It is observed that vortical structure and wind shear were generated at leading edge and tower with high velocity deficit and flow separation. High magnitude of flow noise was observed in low frequency range which is from 30 Hz to 60 Hz. It was observed that vortical structure at leading edge was generated in frequency range from 33.3 Hz to 41.6 Hz. Temporal characteristic in vortical structure at leading edge was similar to noise characteristics, having the similar frequency ranges.
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.
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.
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.