• Title/Summary/Keyword: BGK model

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A FEASIBILITY STUDY OF A NAVIER-STOKES FLOW SOLVER USING A KINETIC BGK SCHEME IN TRANSITIONAL REGIME (Kinetic BGK 기법을 이용한 Navier-Stokes 유동 해석자의 천이 영역 적용성 연구)

  • Cho, M.W.;Yang, T.H.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.20 no.3
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    • pp.54-61
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    • 2015
  • In the present study, a flow solver using a kinetic BGK scheme was developed for the compressible Navier-Stokes equation. The kinetic BGK scheme was used to simulate flow field from the continuum up to the transitional regime, because the kinetic BGK scheme can take into account the statistical properties of the gas particles in a non-equilibrium state. Various numerical simulations were conducted by the present flow solver. The laminar flow around flat plate and the hypersonic flow around hollow cylinder of flare shape in the continuum regime were numerically simulated. The numerical results showed that the flow solver using the kinetic BGK scheme can obtain accurate and robust numerical solutions. Also, the present flow solver was applied to the hypersonic flow problems around circular cylinder in the transitional regime and the results were validated against available numerical results of other researchers. It was found that the kinetic BGK scheme can similarly predict a tendency of the flow variables in the transitional regime.

Numerical simulation and development of scheme for compressible flows(Application of BGK method) (압축성 유동의 수치해석 및 수치해법 개발(BGK 기법의 적용))

  • 신동신;김종암;노오현
    • Journal of the Korean Society of Propulsion Engineers
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    • v.5 no.1
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    • pp.1-9
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    • 2001
  • BGK schemes are developed by improving the standard BGK numerical method. Shceme 1 uses the Osher's Godunov type solution and scheme 2 are developed to overcome the problems of scheme 1.The improved schemes show many unique properties such as entropy condition, positivity condition, higher order gas evolution model, which lead to an high degree of robustness and accuracy. The scheme 2 especially overcomes the shortcomings of the scheme 1 and posseses many superior properties that cannot be found ohter numerical schemes, and is expected to apply various problems with high accuracy and robustness.

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Fluid analysis of edge Tones at low Mach number using the finite difference lattice Boltzmann method (차분격자볼츠만법에 의한 저Mach수 영역 edge tone의 유체해석)

  • Kang H. K.;Kim J. H.;Kim Y. T.;Lee Y. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.113-118
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    • 2004
  • This paper presents a two-dimensional edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle by the finite difference lattice Boltzmann method (FDLBM). We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of $\alpha=23^0$. At a stand-off distance $\omega$, the edge is inserted along the centreline of the jet, and a sinuous instability wave with real frequency f is assumed to be created in the vicinity of the nozzle and th propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. Its interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips. The lattice BGK model for compressible fluids is shown to be one of powerful tool for computing sound generation and propagation for a wide range of flows.

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Direct Simulation of Acoustic Sound by the Finite Difference Lattice Boltzmann Method (차분격자볼츠만법에 의한 유체음의 직접계산)

  • Kang, Ho-Keun;Ro, Ki-Deok;Lee, Young-Ho
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1827-1832
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    • 2003
  • In this research, the simulation method for acoustic sounds by a uniform flow around a two-dimensional circular cylinder by using the finite difference lattice Boltzmann model is explained. To begin with, we examine the boundary condition which determined with the distribution function $f_i^{(0)}$ concerning with density, velocity and internal energy at boundary node. Very small acoustic pressure fluctuation, with same frequency as that of Karman vortex street, is compared with the pressure fluctuation around a circular cylinder. The acoustic sound' propagation velocity shows that acoustic approa ching the upstream, due to the Doppler effect in the uniform flow, slowly propagated. For the do wnstream, on the other hand, it quickly propagates. It is also apparently the size of sound pressure was proportional to the central distance $r^{-1/2}$ of the circular cylinder. The lattice BGK model for compressible fluids is shown to be one of powerful tool for simulation of gas flows.

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Numerical Simulation of Shock Propatation by the Finite Difference Lattice Boltzmann Method

  • Kang, Ho-Keun;Tsutahara, Michihisa;Kim, Jeong-Hwan;Lee, Young-Ho
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.468-474
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    • 2001
  • The shock process represents an abrupt change in fluid properties, in which finite variations in pressure, temperature, and density occur over a shock thickness which is comparable to the mean tree path of the gas molecules involved. The fluid phenomenon is simulated by using finite difference lattice Boltzmann method (FDLBM). In this research, the new model is proposed using the lattice BGK compressible fluid model in FDLBM for the purpose of shortening in calculation time and stabilizing in simulation operation. The numerical results agree also with the theoretical predictions.

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Numerical Simulation of Aerodynamic Sound by the Finite Difference Lattice Boltzmann Method (차분격자볼츠만법에 의한 유동소음의 수치계산)

  • 강호근;김은라
    • Journal of Ocean Engineering and Technology
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    • v.18 no.2
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    • pp.10-17
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    • 2004
  • In this research, a numerical simulation for the acoustic sounds around a two-dimensional circular cylinder in a uniform flaw was developed, using the finite difference lattice Boltzmann model. We examine the boundary condition, which is determined by the distribution function concerning density, velocity, and internal energy at the boundary node. Pressure variation, due to the emission of the acoustic waves, is very small, but we can detect this periodic variation in the region far from the cylinder. Daple-like emission of acoustic waves is seen, and these waves travel with the speed of sound, and are synchronized with the frequency of the lift on the cylinder, due to the Karman vortex street. It is also apparent that the size of the sound pressure is proportional to the central distance to the circular cylinder. The lattice BGK model for compressible fluids is shown to be a powerful tool for the simulation of gas flaws.

Numerical Simulation of Shock Wave Propagation using the Finite Difference Lattice Boltzmann Method

  • Kang, Ho-Keun;Michihisa Tsutahara;Ro, Ki-Deok;Lee, Young-Ho
    • Journal of Mechanical Science and Technology
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    • v.16 no.10
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    • pp.1327-1335
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    • 2002
  • The shock wave process represents an abrupt change in fluid properties, in which finite variations in pressure, temperature, and density occur over the shock thickness which is comparable to the mean free path of the gas molecules involved. This shock wave fluid phenomenon is simulated by using the finite difference lattice Boltzmann method (FDLBM). In this paper, a new model is proposed using the lattice BGK compressible fluid model in FDLBM for the purpose of speeding up the calculation as well as stabilizing the numerical scheme. The numerical results of the proposed model show good agreement with the theoretical predictions.

Analysis of Microchannel Flows Using a Model Boltzmann Equation (모델 볼츠만방정식을 이용한 마이크로채널 유동 해석)

  • Chung C. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.03a
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    • pp.99-105
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    • 2004
  • 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.

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NUMERICAL ANALYSIS OF GAS FLOWS IN ULTRA-THIN FILM GAS BEARINGS USING A MODEL BOLTZMANN EQUATION (모델볼츠만 방정식을 이용한 초박막 개스베어링 기체유장 수치해석)

  • Chung, C.H.
    • Journal of computational fluids engineering
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    • v.14 no.1
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    • pp.86-95
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    • 2009
  • 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.

Numerical Analysis of Low-Speed Flows in Micro-Channels (마이크로채널 내부의 저속 유동장 수치해석)

  • Chung C. H.
    • Journal of computational fluids engineering
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    • v.9 no.2
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    • pp.36-42
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    • 2004
  • 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 are made for flows in simple micro-channels 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 Wavier-Stokes equations. It is shown that the present method is a useful tool for the modeling of low-speed flows in micro-channels.