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전산유체역학을 활용한 자주도하장비 문교 상태의 저항 및 자항 성능 평가
이인수(I. Lee),서정화(J. Seo),석우찬(W. Seok),유재훈(J. Yoo),이강일(K.I. Lee),김도헌(D.H. Kim),이남훈(N. Lee),이성오(S.O. Lee),이신형(S.H. Lee) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.4
In this study, numerical simulations were conducted for resistance and self-propulsion performance for an amphibious rig in ferry mode. They were performed under conditions of h/T=4.5, 2.0 and head angles of both 180 and 90 degrees using SNUFOAM, based on open source CFD toolkit OpenFOAM. A double body method was adopted for free surface flow. Thrust was modeled with a body force method in self propulsion tests. The results of resistance tests showed drag forces according to the depth and head angle conditions and presented differences in the drag forces. In order to investigate the differences, the pressure, velocity, and vorticity distribution near the amphibious rig were identified. From self propulsion tests results, the thrusts and powers at the self propulsion point were estimated and compared with the thrust diagram to confirm the self propulsion performance.
해파리 추진 방식을 응용한 합성 제트 추진기 형상 설계 및 분석
이혁수(H. Lee),장진관(J. Jang),석우찬(W. Seok),여홍구(H.G. Yeo),이신형(S.H. Rhee) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.1
Synthetic jet thrusters are zero-net mass flux thrusters for low speed underwater vehicles inspired by the pulsatile jet propulsion of jellyfish and squid. In this paper, OpenFOAM libraries are used to analyze vortex ring formation and energy efficiency of synthetic jet thrusters with varying diameters and lengths of nozzles. Synthetic jet thrusters are modeled in the axisymmetric domain and dynamic mesh is used to simulate the sinusoidal motion of pistons. The flow field, circulation, and ratio of the change in kinetic energy to the piston work are computed during the first two cycles of moving piston. As a result, the vortex ring formation is enhanced by the change in velocity distribution at the nozzle exit due to the flow generated in the relaxation phase. Furthermore, the nozzle with the diameter ratio of 0.6 and zero-length shows the highest efficiency.
고선호(S.H. Ko),최학규(H.K. Choi),이희범(H.B. Lee),이신형(S.H. Rhee) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.3
A fishway is a structure on or around artificial and natural barriers, such as dams, locks and waterfalls, to help fishes natural migration. In this paper, a computational fluid dynamics (CFD) code, termed SNUFOAM is used to analyze vertical hydraulic characteristic of rollway of fishway. Volume-of-fluid (VOF) method was used to handle free-surface. It is important to determine the factors influencing flow characteristics in fishway because fish use directional information from the flow characteristics to navigate through fishway. Fishway was modeled in 2-D and the influence of the stream velocity, slope, and weir height of fishway was tested. In results, the transition Reynolds number was 2×10<SUP>5</SUP> ~ 3×10<SUP>5</SUP>.
자유수면의 경계면에서 해의 번짐을 줄이기 위한 경계면 압축 기법 및 주상체에의 적용
이희범(H. Lee),이신형(S. H. Rhee),김동진(D. J. Kim),김선영(S. Y. Kim),박선호(S. Park) 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.5
A high speed planing hull is mostly supported by hydrodynamic lift force rather than buoyancy force. The lift force directly influences the running attitude of the planing hull such as trim and sinkage. And the pressure distribution is strongly related to the solution of a free-surface flow around a planing hull. To handle free-surface flow volume-of-fluid (VOF) method have been widely used even it has a disadvantages of interface smearing. In the present study, a new dynamic interface compression method were introduced to reduce interface smearing and avoid unphysical solution. The dynamic compression consists of a function of angle of the flow direction and free-surface. The method was implemented and validated by prismatic body problem.
조류발전용 수평축터빈의 단독성능 평가를 위한 수치 해석법
이주현(J.H. Lee),김동환(D.J. Kim),이신형(S.H. Rhee),김문찬(M.C. Kim),현범수(B.S. Hyun),남종호(J.H. Nam) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
Recently, due to high oil prices and environmental pollution issues, interest of alternative energy development increases and the related research is widely conducted. Among those research activities, the tidal stream power generation utilizes the tidal flow as its mechanical power resource and less depends on the environmental condition for installation and operation than other renewable energy resources. Therefore the amount of power generated is quite consistent and straightforward to predict. However, research on the tidal stream energy conversion turbine is rarely found. In the present study, two numerical methods were developed and compared for the open water Momentum Theory, which is widely used for wind turbines, was adopted. The moving reference frame method for Computational Fluid Dynamis solver were also used. Hybrid meshing was used for the complex geometry of turbines. The analysis results using each method were compared to figure out a better method for the performance prediction.