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정찬홍(C. H. Chung) 한국전산유체공학회 2004 한국전산유체공학회 학술대회논문집 Vol.2004 No.-
A kinetic theory analysis is made of low-speed gas flows around a micro-plate. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. The method does not suffer from statistical noise which is common in particle based methods and requires much less amount of computational effort. Calculations are made for flows around a micro-scale flat plate with a finite length of 20 microns. The method is assessed by comparing the results with those from several different methods and available experimental data.
정찬홍(C. H. Chung) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.4
A kinetic theory analysis is used to study the ultra-thin gas flow field in a gas slider bearing. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for a flow in a micro-channel between an inclined slider and a moving disk drive platter. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle-based methods and requires much less computational effort.
정찬홍(C. H. Chung) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.3
A kinetic theory analysis is made of low-speed rarefied gas flows around a flat plate. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. The method does not suffer from statistical noise which is common in particle based methods and requires much less amount of computational effort. Calculations are made for flows around a micro-scale flat plate with a finite length of 20 microns. The method is assessed by comparing the results with those from several different methods and available experimental data.
정찬홍(C. H. Chung) 한국전산유체공학회 2004 한국전산유체공학회지 Vol.9 No.2
Low-speed gas flows in micro-channels are investigated using a kinetic theory analysis. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations arc made for flows in simple micro~channe1s and a micro-fluidic system consisting of two micro-channels in series. The results are compared well with those from the DSMC method and an analytical solutions to the Navier-Stokes equations. It is shown that the present method is a useful tool for the modeling of low-speed flows in micro-channels.
Comparison of FDDO and DSMC Methods in the Analysis of Expanding Rarefied Flows
정찬홍(C. H. Chung) 한국전산유체공학회 1996 한국전산유체공학회지 Vol.1 No.1
이차원 노즐을 통하여 저밀도 환경으로 팽창하는 희박류의 분석에 있어서 불연속좌표법과 결합된 유한차분 (Finite difference method coupled with the discrete-ordinate method, FDDO)과 직접모사법 (direct-simulation Monte Carlo method, DSMC)이 비교되었다. FDDO를 이용한 분석에서는 충돌적분모델을 도입하여 간단해진 볼츠만식(Boltzmann equation)이 불연속좌표법을 이용하여 물리적 공간에서는 연속이나 분자속도 공간에서는 불 연속좌표로 표시되는 면미분방정식군으로 변환되어 유한차분법에 의하여 수치해석 되었다. 직접모사법에서는 분자모델로 가변강구모델(variable hard sphele model, VHS)이, 충돌샘플 링모델로는 비시계수법(no time counter method, NTC)이 채택되었다. 전혀 다른 두 가지 방법에 의한 노즐 내부에서의 유체흐름 해석결과는 매우 잘 일치하였으며, 노즐 외부의 plume 영역에서는 FDDO에 의한 해석결과가 직접모사법에 의한 해석결과에 비하여 약간 느린 팽창을 보였다.
정찬홍(C. H. Chung) 한국전산유체공학회 2004 한국전산유체공학회 학술대회논문집 Vol.2004 No.-
A kinetic theory analysis is made of low-speed gas flows in microchannels. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. The method does not suffer from statistical noise which is common in particle based methods and requires much less amount of computational effort. Calculations are made for flows in simple microchannels and a microfluidic system consisting of two microchannels in series. The method is assessed by comparing the results with those from several different methods and available experimental data.
화학반응을 수반하는 극초음속 희박류 유동의 직접모사법 개발
정찬홍(C. H. Chung),윤성준(S. J. Yoon) 한국전산유체공학회 1999 한국전산유체공학회지 Vol.4 No.3
A Direct simulation Monte-Carlo (DSMC) code is developed. which employs the Monte-Carlo statistical sampling technique to investigate hypersonic rarefied gas flows accompanying chemical reactions. The DSMC method is a numerical simulation technique for analyzing the Boltzmann equation by modeling a real gas flow using a representative set of molecules. Due to the limitations in computational requirements, the present method is applied to a flow around a simple two-dimensional object in exit velocity of 7.6 km/see at an altitude of 90 km. For the calculation of chemical reactions an air model with five species (O₂, N₂, O, N, NO) and 19 chemical reactions is employed. The simulated result showed various rarefaction effects in the hypersonic flow with chemical reactions.
모델볼츠만 방정식을 이용한 초박막 개스베어링 기체유장 수치해석
정찬홍(C.H. Chung) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.1
A kinetic theory analysis is used to study the ultra-thin gas flow field in gas bearings. The Boltzmann equation simplified by a collision model is solved by means of a finite difference approximation with the discrete ordinate method. Calculations are made for flows inside micro-channels of backward-facing step, forward-facing step, and slider bearings. The results are compared well with those from the DSMC method. The present method does not suffer from statistical noise which is common in particle based methods and requires less computational effort.
화학반응을 수반하는 극초음속 희박류 유동의 직접모사법 개발
정찬홍(C. H. Chung),윤성준(S. J. Yoon) 한국전산유체공학회 1999 한국전산유체공학회지 Vol.4 No.3
A Direct simulation Monte-Carlo (DSMC) code is developed. which employs the Monte-Carlo statistical sampling technique to investigate hypersonic rarefied gas flows accompanying chemical reactions. The DSMC method is a numerical simulation technique for analyzing the Boltzmann equation by modeling a real gas flow using a representative set of molecules. Due to the limitations in computational requirements, the present method is applied to a flow around a simple two-dimensional object in exit velocity of 7.6 km/see at an altitude of 90 km. For the calculation of chemical reactions an air model with five species (O₂, N₂, O, N, NO) and 19 chemical reactions is employed. The simulated result showed various rarefaction effects in the hypersonic flow with chemical reactions.