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Sitorus, Patar Ebenezer,Park, JineSoon,Ko, Jin Hwan The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
In recent years, nonlinear dynamic models have been developed for flapping-type energy harvesting systems with a rigid wing, but not for those with a flexible wing. Thus, in this study, flexible wing designs of NACA0012 section are proposed and measurements of the forces of rigid cambered wings, which are used to estimate the performance of the designed wings, are conducted. Polar curves from the measured lift and drag coefficients show that JavaFoil estimation is much closer to the measured values than Eppler over the entire given range of angles of attack. As the camber of the rigid cambered wings is increased, both the lift and drag coefficients increase, in turn increasing the resultant forces. Moreover, the maximum resultant forces for all rigid cambered wings are achieved at the same angle of attack as the maximum lift coefficient, meaning that the lift coefficient is dominant in representations of the wing characteristics.
Patar Ebenezer Sitorus,JineSoon Park,Jin Hwan Ko 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
In recent years, nonlinear dynamic models have been developed for flapping-type energy harvesting systems with a rigid wing, but not for those with a flexible wing. Thus, in this study, flexible wing designs of NACA0012 section are proposed and measurements of the forces of rigid cambered wings, which are used to estimate the performance of the designed wings, are conducted. Polar curves from the measured lift and drag coefficients show that JavaFoil estimation is much closer to the measured values than Eppler over the entire given range of angles of attack. As the camber of the rigid cambered wings is increased, both the lift and drag coefficients increase, in turn increasing the resultant forces. Moreover, the maximum resultant forces for all rigid cambered wings are achieved at the same angle of attack as the maximum lift coefficient, meaning that the lift coefficient is dominant in representations of the wing characteristics.
다리우스 터빈 성능에 대한 가변 형상 블레이드의 영향 연구
고진환,Patar Ebenezer Sitorus,김지훈 한국해양환경·에너지학회 2019 한국해양환경·에너지학회지 Vol.22 No.1
The Darius turbine is one of the typical vertical axis flow turbines, but it has disadvantages such as low efficiency, shaking etc. In this study, we implemented a variable shape blade and investigated the per-formance improvement through open water channel experiments. Variable pitch and variable pitch-camber were chosen for the variable shape, and aircraft-flap based mechanism was devised for the variable pitch-camber. Both the variable pitch and the variable pitch-camber showed noticeable differ-ence from the fixed pitch at the limited pitch angle of 10 degrees and the performance was improved by increasing the efficiency and moving to the lower TSR (tip speed ratio). Also, it was indicated that TSRs of the variable pitch-camber shifted to lower values than those of the variable pitch due to the superposition effect of pitch and camber. The experimental results show that the performance of the variable shape blades can be improved and the competitiveness of the Darius turbine is expected to be improved through practical experi-mental validation studies. 다리우스 터빈은 수직축 방식으로 대표적 유동 터빈 중 하나이나 낮은 효율, 흔들림 등 단점을 가지고 있다. 본 연구에서는 가변 형상 블레이드를 구현하고 이를 통한 성능 향상 여부를 개수로 실험을 통해 알아보고자 하였다. 가변 형상의 경우 가변 피치와 가변 피치-캠버가 사용되었고 가변 피치-캠버의 경우는 항공기의 플랩(flap)에 근거한 메커니즘이 고안되었다. 가변 피치와 가변 피치-캠버 두 가지 경우 모두 한계 피치각 10도에서 고정 피치와의 차이점이 두드러졌으며, 효율 증가와 낮은 TSR(tip speed ratio)로의 이동으로 성능이 향상됨을 확인하였다. 또한 가변 피치-캠버의 TSR이 피치와 캠버의 중첩 효과에 기인하여 가변 피치의 TSR보다 더 낮은 값으로 이동하는 것을 확인하였다. 본 실험 연구를 통해 가변 형상 블레이드의 성능 향상 가능성을 볼 수 있었고 향후 이에 대한 실용적인 실험 검증 연구들을 통해 다리우스 터빈의 경쟁력을 높일 수 있을 것으로 기대된다.
유동가시화를 통한 다중 수중익 덕트 내 유속조절에 대한 연구
김지훈(Jihoon Kim),Patar Ebenezer Sitorus,원보름(Boreum Won),Tuyen Quang Le,고진환(Jin Hwan Ko) 한국가시화정보학회 2016 한국가시화정보학회지 Vol.14 No.2
In this work, we investigate the flow velocity controllability of a diffuser-type multiple hydrofoil duct by experimental and numerical flow visualization approaches. The flow velocity controllability is analyzed by changing the angle of the hydrofoil near the outlet, which is the diffuser, while the incoming flow velocity is 0.6 ㎧ in the experiment. When the diffuser angle is changed from 0 to 7.5 degree, the maximum velocity inside the duct is varied from 1.35 ㎧ to 1.52 ㎧. Also, it is shown from the numerical analysis that the maximum velocity is varied from 1.09 ㎧ to 1.17 ㎧ in the same condition. Thus, the aspect of the acceleration in the duct due to the increase of the diffuser angle is similar between the both approaches. Therefore, the multiple hydrofoil duct can be used to control the flow speed inside the duct for continuously extracting power close to a rated capacity.