• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.144-151
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• 2001

NURBS 곡면식으로 정의된 물체 표면상에서 표면 정렬 격자를 생성할 수 있는 방법을 소개하였다. 공학 응용분야에서의 물체 표면 정의는 여러 개의 패치들로 표현되는 것이 일반적이고, 여기서 소개하는 표면격자 생성기법은 이러한 여러 패치들에 걸쳐서 분포되는 정렬격자를 쉽게 생성할 수 있도록 한다 이 기법은 매개변수 형태의 타원형 격자생성 방정식의 해를 구하되, 여러 NURBS 패치에 걸쳐서 투영/분포된 초기 격자계를 타원형 방정식 반복계산 과정의 매개변수형 표면 정의식으로 임시 활용한다. 매개변수형 타원형 방정식의 해가 얻어지고 나면, 그 결과 격자계를 다시 NURBS 패치에 투영을 시키고 타원형 방정식의 해를 구하는 과정이 반복된다. 이러한 반복과정이 전체적으로 수렴이 이루어질 때까지 반복된다. 이 방법에 의해서 얻어지는 표면 정렬 격자계들은 타원형 격자생성기법의 특징인 완만성을 가지면서 정의된 물체표면에서 벗어나지 않는 격자점들이 된다. 소개된 방법은 간단하면서도 하나의 NURBS 곡면만이 아니라 여러 개의 NURBS 곡면에 걸쳐있는 정렬격자계를 효율적으로 생성할 수 있도록 해주며, 그 기본적인 접근법은 NURBS 곡면식 만이 아니라 다른 형태의 매개변수형 형상 정의식에도 적용이 가능하다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.1-7
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• 2006

In the present study, A 3-D chimera technique for overlapped bodies in relative motion is studied using unstructured meshes. If all node points of a mesh element at solid boundary are in another body, this element is excluded from computational domain. For computation of unsteady flow, non-active cells have proper variables using interpolation and extrapolation. These variables are used in next time step. The motion of a launching trajectory ejected from a wing and the motion of deploying fins of a trajectory which have not been simulated are computed to conform practicality of this technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1680-1686
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• 2010

Optical fiber Bragg grating to have the lowest transmitivity at 1549.9nm wavelength was fabricated using a Gaussian distributed KrF Eximer laser of 248nm lasing wavelength and a phase mask of 1.072um period. The proper alignment of an optic setup to fabricate fiber gratings was investigated and the reproductivity of the grating fabrication was examined using the obtained optimum fabrication condition in this experiment.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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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.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.10
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• pp.669-676
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• 2022

In this paper, the carriage load analyses of stores installed on aircraft are conducted to validate the chimera grid method applied to an unstructured CFD solver, UMSAPv. First, the chimera grid method of UMSAPv is verified for the well-known Eglin Wing/Pylon/Finned store problem. Next, an angle of attack sweep of F/A-18C clean configuration is conducted at a subsonic speed. The computed results are compared with the results of the previous study using MSAPv, a structured CFD solver, to show the validity of Umsapv. Finally, the carriage of F/A-18C JDAM is carried out with a chimera grid as well as a single block grid. The computed results are compared with other computational, experimental and the flight tests.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.231.1-231.1
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• 2005

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.723-733
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• 2011

A numerical method of the CSF(Continuum Surface Force) model is presented for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The application of the present method to a 2-D liquid drop problem is illustrated by an equilibrium and nonequilibrium oscillating drop calculation. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.561-567
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• 2011

The inverse radiation analysis of a two-dimensional irregular configuration using unstructured triangular meshes is presented. In this study, an enclosure filled with an absorbing, emitting and scattering medium with diffusely emitting and reflecting opaque boundaries is considered. The finite volume method is applied to solve the radiative transfer equation in order to simulate the measured incident radiation values which are used as input data for the inverse analysis. The conjugate gradient method is adopted for the estimation of wall emissivities by minimizing the objective function at each iteration step. To verify the performance of the unstructured grid system, we compare the results with those using a structured grid system for the two-dimensional lopsided shape. The effect of measurement errors on the estimation accuracy is also investigated.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.294-301
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• 2011

A two-dimensional hybrid flaw solver has been developed for the accurate and efficient simulation of steady and unsteady flaw fields. The flow solver was cast to accommodate two different topologies of computational meshes. Triangular meshes are adopted in the near-body region such that complex geometric configurations can be easily modeled, while adaptive Cartesian meshes are, utilized in the off-body region to resolve the flaw more accurately with less numerical dissipation by adopting a spatially high-order accurate scheme and solution-adaptive mesh refinement technique. A chimera mesh technique has been employed to link the two flow regimes adopting each mesh topology. Validations were made for the unsteady inviscid vol1ex convection am the unsteady turbulent flaws over an NACA0012 airfoil, and the results were compared with experimental and other computational results.