• Title, Summary, Keyword: Overset mesh method

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CONSERVATIVE OVERSET MESH TECHNIQUE ON 2-D UNSTRUCTURED MESHES (이차원 비정렬 격자계에서의 보존적 중첩 격자 기법)

  • Jung, M.S.;Kwon, O.J.;Kang, H.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.27-32
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    • 2008
  • In the present study, a conservative overset mesh technique has been developed on 2-D unstructured meshes. A new domain connection technique between independent mesh blocks was proposed to satisfy the conservation of mass, momentum, or energy in entire computational domain. The present technique was applied to several classical computational problems to validate the superiority of the conservative method to the non-conservative method.

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CONSERVATIVE OVERSET MESH TECHNIQUE ON 2-D UNSTRUCTURED MESHES (이차원 비정렬 격자계에서의 보존적 중첩 격자 기법)

  • Jung, M.S.;Kwon, O.J.;Kang, H.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.27-32
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    • 2008
  • In the present study, a conservative overset mesh technique has been developed on 2-D unstructured meshes. A new domain connection technique between independent mesh blocks was proposed to satisfy the conservation of mass, momentum, or energy in entire computational domain. The present technique was applied to several classical computational problems to validate the superiority of the conservative method to the non-conservative method.

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Aerodynamic Shape Optimization using Discrete Adjoint Formulation based on Overset Mesh System

  • Lee, Byung-Joon;Yim, Jin-Woo;Yi, Jun-Sok;Kim, Chong-Am
    • International Journal of Aeronautical and Space Sciences
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    • v.8 no.1
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    • pp.95-104
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    • 2007
  • A new design approach of complex geometries such as wing/body configuration is arranged by using overset mesh techniques under large scale computing environment. For an in-depth study of the flow physics and highly accurate design, several special overlapped structured blocks such as collar grid, tip-cap grid, and etc. which are commonly used in refined drag prediction are adopted to consider the applicability of the present design tools to practical problems. Various pre- and post-processing techniques for overset flow analysis and sensitivity analysis are devised or implemented to resolve overset mesh techniques into the design optimization problem based on Gradient Based Optimization Method (GBOM). In the pre-processing, the convergence characteristics of the flow solver and sensitivity analysis are improved by overlap optimization method. Moreover, a new post-processing method, Spline-Boundary Intersecting Grid (S-BIG) scheme, is proposed by considering the ratio of cell area for more refined prediction of aerodynamic coefficients and efficient evaluation of their sensitivities under parallel computing environment. With respect to the sensitivity analysis, discrete adjoint formulations for overset boundary conditions are derived by a full hand-differentiation. A smooth geometric modification on the overlapped surface boundaries and evaluation of grid sensitivities can be performed by mapping from planform coordinate to the surface meshes with Hicks-Henne function. Careful design works for the drag minimization problems of a transonic wing and a wing/body configuration are performed by using the newly-developed and -applied overset mesh techniques. The results from design applications demonstrate the capability of the present design approach successfully.

Numerical Simulation of Unsteady Rotor Flow Using an Unstructured Overset Mesh Flow Solver

  • Jung, Mun-Seung;Kwon, Oh-Joon
    • International Journal of Aeronautical and Space Sciences
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    • v.10 no.1
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    • pp.104-111
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    • 2009
  • An unstructured overset mesh method has been developed for the simulation of unsteady flow fields around isolated rotors and rotor-fuselage configurations. The flow solver was parallelized for the efficient calculation of complicated flows requiring a large number of cells. A quasi-unsteady mesh adaptation technique was adopted to enhance the spatial accuracy of the solution and to better resolve the rotor wake. The method has been applied to calculate the flow fields around rotor-alone and rotor-fuselage configurations in forward flight. Validations were made by comparing the predicted results with those of measurements. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

DEVELOPMENT OF AN UNSTRUCTURED OVERSET MESH METHOD FOR 2-D UNSTEADY VISCOUS FLOW SIMULATION WITH RELATIVE MOTION (상대운동이 있는 이차원 비정상 점성 유동 해석을 위한 비정렬 중첩격자기법 개발)

  • Jung Mun-Seung;Kwon Oh-Joon
    • Journal of computational fluids engineering
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    • v.11 no.2
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    • pp.1-7
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    • 2006
  • An unstructured overset mesh method has been developed for the simulation of unsteady viscous flow fields around multiple bodies in relative motion. For this purpose, a robust and fast search technique is proposed for both triangle and high-aspect ratio quadrilateral cell elements. The interpolation boundary is defined for data communication between grid systems and an interpolation method is suggested for viscous and inviscid cell elements. This method has been applied to calculate the flow fields around 2-D airfoils involving relative motion. Validations were made by comparing the predicted results with those of experiments or other numerical results. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

DEVELOPMENT OF AN UNSTRUCTURED OVERSET MESH METHOD FOR 2-D UNSTEADY VISCOUS FLOW ANALYSIS (이차원 비정상 점성 유동 해석을 위한 비정렬 중첩격자기법 개발)

  • Jung M. S.;Kwon O. J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.135-139
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    • 2005
  • An unstructured overset mesh method has been developed for the simulation of unsteady viscous flow fields around multiple bodies in relative motion. For this purpose, a robust and fast search technique is proposed for both triangle and high-aspect quadrilateral cell elements. The interpolation boundary is defined for data communication between grid systems and an interpolation method is suggested for viscous and inviscid cell elements. This method has been applied to calculate the flow fields around 2-D airfoil including relative motion. Validation were made by comparing the predicted results with those of experiments or other researcher's numerical results. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

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Numerical Simulation of Rotor-Fuselage Aerodynamic Interaction Using an Unstructured Overset Mesh Technique

  • Lee, Bum-Seok;Jung, Mun-Seung;Kwon, Oh-Joon;Kang, Hee-Jung
    • International Journal of Aeronautical and Space Sciences
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    • v.11 no.1
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    • pp.1-9
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    • 2010
  • Numerical simulation of unsteady flows around helicopters was conducted to investigate the aerodynamic interaction of main rotor and other components such as fuselage and tail rotor. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between the main rotor, and other components. As the application of the present method, calculations were made for the rotor-fuselage aerodynamic interaction of the ROBIN (ROtor Body INteraction) configuration and for a complete UH-60 helicopter configuration consisted of main rotor, fuselage, and tail rotor. Comparison of the computational results was made with measured time-averaged and instantaneous fuselage surface pressure distributions for the ROBIN configuration and thrust distribution and available experimental data for the UH-60 configuration. It is demonstrated that the present method is efficient and robust for the simulation of complete rotorcraft configurations.

DEVELOPMENT OF AERODYNAMIC SHAPE OPTIMIZATION TOOLS FOR MULTIPLE-BODY AIRCRAFT GEOMETRIES OVER TRANSONIC TURBULENT FLow REGIME (천음속 난류 유동장에서의 다중체 항공기 형상의 공력 설계 도구의 개발)

  • Lee, B.J.;Lee, J.S.;Yim, J.W.;Kim, Chong-Am
    • 한국전산유체공학회:학술대회논문집
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    • pp.100-110
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    • 2007
  • A new design approach for a delicate treatment of complex geometries such as a wing/body configuration is arranged using overset mesh technique under large scale computing environment for turbulent viscous flow. Various pre- and post-processing techniques which are required of overset flow analysis and sensitivity analysis codes are discussed for design optimization problems based on gradient based optimization method (GBOM). The overset flow analysis code is validated by comparing with the experimental data of a wing/body configuration (DLR-F4) from the 1st Drag Prediction Workshop (DPW-I). In order to examine the applicability of the present design tools, careful design works for the drag minimization problem of a wing/body configuration are carried out by using the developed aerodynamic shape optimization tools for the viscous flow over multiple-body aircraft geometries.

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Numerical Simulation of Airframe Separation of a Missile System Using an Unstructured Overset Mesh Technique (비정렬 중첩격자기법을 이용한 유도무기의 기체분리운동 모사)

  • Jeong, Mun-Seung;Lee, Sang-Uk;Gwon, O-Jun;Heo, Gi-Hun;Byeon, U-Sik
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.5
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    • pp.19-29
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    • 2006
  • In this study, numerical simulation of airframes separating from a missile system has been preformed. For the time-accurate trajectory simulation, six D.O.F equations of motion of multiply connected bodies were derived and these equations have been coupled with the unstructured overset mesh technique for the treatment of independent mesh blocks moving with each body component. Applications were made for the simulation of the airframe separation at missile angles of attack of 0 and 5 degrees. It was demonstrated that the present method is efficient and robust for the prediction of unsteady time-accurate flow fields involving multiple bodies in relative motion.

An Unstructured Mesh Technique for Rotor Aerodynamics

  • Kwon, Oh-Joon
    • 한국전산유체공학회:학술대회논문집
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    • pp.24-25
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    • 2006
  • An unstructured mesh method has been developed for the simulation of steady and time-accurate flows around helicopter rotors. A dynamic and quasi-unsteady solution-adaptive mesh refinement technique was adopted for the enhancement of the solution accuracy in the local region of interest involving highly vortical flows. Applications were made to the 2-D blade-vortex interaction aerodynamics and the 3-D rotor blades in hover. The interaction between the rotor and the airframe in forward flight was investigated by introducing an overset mesh technique.

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