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세장형 물체 주의 고앙각 유동의 비대칭 와류 및 측력 특성에 관한 수치적 연구
정성기(S.K. Jung),정재홍(J.H. Jung),명노신(R.S. Myong),조태환(T.H. Cho) 한국전산유체공학회 2006 한국전산유체공학회지 Vol.11 No.3
Flow around a guided missile in high maneuver. i.e. at a high angle of attack. shows complex phenomena. It is well known that even in geometrically symmetric conditions the flow around a missile at high angles of attack can generate unexpected large side forces and yaw moments due to asymmetric vortices. In this paper, a CFD code (FLUENT) based on the Navier-Stokes equations was used for the numerical analysis to find a suitable numerical mechanism for generation of asymmetric vortices. It is shown that a numerical technique of applying different surface roughness to a specific area of the missile nose surface gives the best fit in comparison with the experimental results. In addition, a numerical investigation of variations of side forces and pressure distributions with angle of attack and roll angle was conducted for the purpose of identifying the source of vortex asymmetries.
항공기 결빙 예측을 위한 Eulerian 기반 액적 충돌 및 결빙 증식 코드
정성기(S.K. Jung),명노신(R.S. Myong),조태환(T.H. Cho) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.2
As a step toward accurate prediction of droplet impingement and ice accretion on aircraft, an Eulerian-based droplet impingement and ice accretion code for air flows around an airfoil containing water droplets is developed. A CFD solver based on the finite volume method was also developed to solve the clean airflow. The finite-volume-based approach for simulating droplet impingement on an airfoil was employed owing to its compatibility with the CFD solver and robustness. For ice accretion module, a simple model based on the control volume is combined with the droplet impingement module that provides the collection efficiency. To validate the present code, it is compared with NASA Glenn IRT (Icing Research Tunnel) experimental data and other well-known icing codes such as LEWICE and FENSAP-ICE. It is shown that the collection efficiency and shape of ice accretion are in good agreement with previous experimental and simulation results.
에어포일의 결빙에 의한 실속 및 항력 특성 변화에 관한 CFD 해석
정성기(S.K. Jung),신성민(S.M. Shin),명노신(R.S. Myong),조태환(T.H. Cho) 한국전산유체공학회 2009 한국전산유체공학회 학술대회논문집 Vol.2009 No.4
The aerodynamic performance of aircraft in icing condition can deteriorate considerably by contamination of aerodynamic and propulsive systems due to icing accretions on aircraft surfaces. A computational analysis based on the Eulerian description was performed on an airfoil to investigate effects of ice accretions on airfoil aerodynamics. A water droplet with liquid water concentration (0.00075㎏/㎥) and mean volume diameter (20㎛) was considered and applied to various angles of attack to investigate the stall angle decrease and the drag increment.
실수기반 다목적 적응영역 유전자 알고리즘과 자가조직도를 이용한 익형 형상 설계 연구
정성기(S.K. Jung),김지홍(J.H. Kim) 한국전산유체공학회 2013 한국전산유체공학회 학술대회논문집 Vol.2013 No.5
An engineering design needs many trade-off studies and an analysis for interrelationship among design parameters to simultaneously fulfil various requirements. Further, in modern aircraft designs, the multi-objective optimization problem is emerged to meet the maximum lift, lift-to-drag ratio and others. Moreover a parameter-based investigation for performance improvement is essential to satisfy further requirements. As this purpose, the Adaptive Range Multi-Objective Genetic Algorithm code was developed, and an interrelationship among design parameters Is analyzed using the Self-Organizing Map. In order to achieve the better maximum lift and lift-to-drag ratio than reference airfoil at landing and cruise conditions, maximum lift coefficient and lift-to-drag ratio were chosen as object functions. Furthermore, the PARSEC method reflecting geometrical properties of airfoil was adopted to generate airfoil shapes. Finally, two airfoils, which show better aerodynamic performance that a reference airfoil, were chosen. as a result, maximum lift coefficient and lift-to-drag ratio were increased of 3.32% and 2.26% for first candidate airfoil and 2.48% and 1.69% for second candidate airfoil. Also interrelationship among design parameters for all candidates is analyzed using the Self-Organizing Map.
정성기(S.K. Jung),오진근(J.G. Oh),전수환(S.H. Chun),문혁(H. Moon),명노신(R.S. Myong),조태환(T.H. Cho) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
Ice accretion on aircraft surface can greatly impair the aerodynamic performance of aircraft. As an alternative to the traditional Lagrangian particle tracking approach, an Eulerian-based droplet impingement and ice accretion code for air flows containing water droplets was developed. A CFD solver was also developed to solve the clean airflow. The results of present method were compared with experimental data and previous icing codes such as LEWICE and FENSAP-ICE and were confirmed to show good agreement each other in qualitative and quantitative ways.
정성기(S. K. Jung),명노신(R. S. Myong),조태환(T. H. Cho),박경린(G. R. Park),강태우(T. W. Kang) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
Ice accretion on aircraft surface can greatly deteriorate the aerodynamic performance of aircraft. Especially, air flows around a wing at glaze ice conditions are very complex and can suffer large aerodynamic penalties. Complicated horn shapes are usually found on the surfaces at glaze ice conditions by coupling effects of heat flux and shear stress. Therefore, the conventional structured CFD method has difficulty in the prediction of glaze ice shape due to its limitation on handling complex geometry. For example, negative cell volumes can be generated in the structured grids in the process of grid regeneration. In order to overcome this limitation, unstructured CFD method was employed to calculate an Eulerian-based droplet field and ice accretion on the surfaces. The developed codes were then compared with experimental data. It was shown that the collective efficiency and iced shape were in good agreement with previous results.
항공기 결빙 액적장 해석을 위한 비정렬 격자 기반의 CFD 기법
정기영(K.Y. Jung),명노신(R.S. Myong),정성기(S.K. Jung) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.11
Ice accretion on aircraft surface plays a critical role in the performance and safety of aircraft. Especially, changes in the external shape of the aircraft due to ice accretion can greatly deteriorate the aerodynamic performance of aircraft. In the study, air flow and droplet impingement codes for prediction of ice accretion on aircraft are developed. A finite volume method CFD solver based on unstructured grids is developed to solve the dean air flow and Eulerian-based droplet field. The codes are then compared with NASA IRT experimental data and computational results obtained by a state-of-the-art icing code. The present prediction is shown to be in close agreement with IRT data.
정기영(K.Y. Jung),안국빈(G.B. Ahn),정성기(S.K. Jung),명노신(R.S. Myong),조태환(T.H. Cho),신훈범(H.B. Shin),정주현(J.H. Jung),최영호(Y.H. Choi),김정훈(J.H. Kim) 한국전산유체공학회 2011 한국전산유체공학회 학술대회논문집 Vol.2011 No.5
Ice accretion on aircraft surface can greatly deteriorate the safety of aircraft. In particular, it can be a cause of impediment for aircraft performances such as aerodynamic characteristics, control, and engine. Numerical simulation of icing accretion based on the state-of-art CFD techniques can be alternative to expensive icing wind tunnel test or flight test. In this study, icing conditions are defined in order to predict the ice accretions around the air intake of aircraft. Then the range and amount of ice accretion on the intake in icing wind tunnel were investigated. In addition, a study on the size effect of icing wind tunnel was conducted in order to check the compatibility with the real in-flight test environment.