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유동 간섭 효과를 고려한 Wing-sails 공력 최적 설계
이학진(H.J. Lee),조영민(Y.M. Jo),권형일(H.I. Kwon),최성임(S.I. Choi) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
These day, an issues related with environments are becoming more pressing. We investigated potential next-generation vessel which makes use of the wing-sails to support existing fossil fuel-based propulsion system. The sailing-ship is a new concept eco-friendly vessel that uses the wind energy to produce additional thrust force by wing-sails above the hull. In this study, we focused on the aerodynamic analysis and design optimization of multiple wing-sails by varying the wind direction 15 degrees to 165 degrees. For the numerical analysis, we solved three dimensional compressible Navier-stokes equation with Spalart-Allmaras turbulent model. After the investigation of aerodynamic characteristics around wing-sails and the effect of flow interactions, we performed the design optimization of wing-sails by considering both single wing-sail and multiple wing-sails. In single wing-sail design, we found optimal value of deflection angle and flap length of single wing-sail to maximize the lift performance. In multiple wing-sails design, we carried out design optimization to find an optimal set-up of individual for each of the wing-sails that maximize total thrust of wing-sails. These optimal set-up include a deflection angle, deflection length and angle of attack of each wing-sails. Using a Kriging-based surrogate model and the derivative-free optimization method of genetic algorithms (GAs), we found the optimal set-up of the single and multiple wing-sails. The design optimization results showed that the total thrust of wing-sails has improved by 27~36% corresponding to the varying the wind directions.
e-Science 기반의 항공우주분야 교육·연구용 공력 최적 설계 프레임워크를 활용한 에어포일의 공력 최적 설계 연구
이학진(H.J. Lee),유민석(M.S. Ryu),권형일(H.I. Kwon),최성임(S.I. Choi) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
In this study, aerodynamic design optimization of airfoil was performed to minimize drag of baseline airfoil at transonic flow by using e-Science based design framework. Prior to the design optimization, parameter sensitivity studies were performed to determine the step-size and the sensitivity of the objective function. In this research, the weight of a Hicks-Henne bump function served as a design variable. Aerodynamic analysis was carried out by EDISON CFD Solver. An aerodynamic design optimization framework of airfoil selected a drag-minimized optimal configuration by using the gradient-based optimization algorithm. Design results showed that the drag and lift performances of an optimized airfoil have been improved by 95% and 7% respectively. In addition, the performance of an optimized airfoil was validated by performing the off-design study in different design flow conditions. Through this study, A aerodynamic design optimization framework of airfoil can be utilized as an educational & research aerodynamic design optimization resource.
이학진(H.J. Lee),조영민(Y.M. Jo),최성임(S.I. Choi),권종오(J.O. Kwon),안성목(S.M. Ahn) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
The sailing ship is a eco-friendly vessels that using wind energy to produce the additional thrust by the hull above the wing-sails. In this study, we performed the aerodynamic analysis around wing-sails by considering the interaction of wing-sails in fixed angle of attack. The wind direction that produces the maximum thrust of wing-sails can be obtained by calculating the thrust of wing-sails with, respect to the wind direction. In the aerodynamic analysis, we used three-dimensional compressible Navier-Stokes equation and hybrid grid to predict more viscous flow of boundary layer. We investigated that the maximum thrust of wing-sails at wind direction of 90 degree. After studying on the flow characteristic around wing-sails and effect of interaction, through derivative free based genetic algorithm and kriging surrogate model method to substitute a objective function evaluation we searched the optimal angle of attack that maximize the thrust of wing-sails. The result of optimization about wind direction of 45, 90 and 135 degree, we acquired about 7~23% of trust increment with trend of increasing the rear wing-sailss angle of attack by the interaction of wing-sails. Also we confirmed the thrust enhancement of 2~18% by conducting a three-dimensional validation.
Lattice-Boltzmann Method를 이용한 제자리 및 전진 비행하는 로터 블레이드의 공력해석
이혁진(H.J. Lee),양진용(J.Y. Yang),명노신(R.S. Myong),이학진(H. Lee) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.4
Numerical analysis of the rotor system has received significant attention due to increased demand and recent developments in Urban Air Mobility (UAM) aircraft with multiple lifting rotors or prop-rotors. In this study, computational analysis was conducted to predict the aerodynamic performance and wake structures of the isolated rotor in the hovering and forward flight conditions using the Lattice-Boltzmann Method (LBM). Caradonna and Tungs rotor was used for the validation model. The thrust and pressure coefficients for various collective pith angles and tip vortex trajectories as a function of wake ages were compared against the measurements. The comparison results showed that the hover performance of the isolated rotor obtained from the LBM simulation was in good agreement with the measured data. Moreover, it was demonstrated that LBM analysis is an efficient way for predicting the cyclic variation in the thrust, asymmetric wake structure, and unsteady vorticity fields that occur in forward flight condition. Calculations showed that LBM simulation is an accurate and efficient prediction method for predicting rotor aerodynamics and wake dynamics, which could be helpful for designing advanced next-generation UAM aircraft.