• Title/Summary/Keyword: DSMC method

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Prediction of Parabolic Antenna Satellite Drag Force in Low Earth Orbit using Direct Simulation Monte Carlo Method (직접모사법을 이용한 지구 저궤도 파라볼릭 안테나 탑재 위성의 항력 예측)

  • Shin, Somin;Na, Kyung-Su;Lee, Juyoung;Cho, Ki-Dae
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.42 no.7
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    • pp.616-621
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    • 2014
  • Consumption of the fuel on the satellite operating in low earth orbit, is increased due to the air resistance and the amount of increase makes the satellite lifetime decrease or the satellite mass risen. Therefore the prediction of drag force of the satellite is important. In the paper, drag force and drag coefficient analysis of the parabolic antenna satellite in low earth orbit using direct simulation monte carlo method (DSMC) is conducted according to the mission altitude and angle of attack. To verify the DSMC simulated rarefied air movement, Starshine satellite drag coefficient according to the altitude and gas-surface interaction are compared with the flight data. Finally, from the analysis results, it leads to appropriate satellite drag coefficient for orbit lifetime calculation.

Numerical Analysis of Ultra-Thin Gas Film Lubrication (초박막 기체윤활의 수치해석)

  • Chung C. H.
    • Journal of computational fluids engineering
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    • v.9 no.4
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    • pp.64-70
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    • 2004
  • 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.

Numerical Analysis of Ultra-Thin Gas Film Lubrication (초박막 기체윤활의 수치해석)

  • Chung C. H.
    • 한국전산유체공학회:학술대회논문집
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    • 2004.10a
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    • pp.207-213
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    • 2004
  • A kinetic theory analysis is used to study the ultra-thin gas flow field in a gas slider bering, 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.

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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.

Kinetic Theory Analysis for Thin-Film Bearings (기체분자운동론을 이용한 박막 베어링 해석)

  • Chung Chan Hong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.162-170
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    • 2004
  • A kinetic theory analysis is used to study the ultra-thin gas flow field in gas slider hearings. 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 the flow field inside stepped and straight slider bearings. The results are compared well with those from the DSMC method. Special attention has been paid to the effect of the pressure build-up in front of a hearing, which has never been assessed before. It has been shown that the pressure build-up at the inlet is about $4.5\%$ of the operating pressure and the resulting load capacity is about $25\%$ higher for the case considered in the present study.

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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.

Generalized Hydrodynamic Computational Models for Diatomic Gas Flows (이원자 기체 유동 해석을 위한 일반유체역학 계산모델 개발)

  • Myong Rho-Shin;Cho Soo-Yong
    • 한국전산유체공학회:학술대회논문집
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    • 2001.05a
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    • pp.111-115
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    • 2001
  • The study of nonlinear gas transport in rarefied condition or associated with the microscale length of the geometry has emerged as an interesting topic in recent years. Along with the DSMC method, several fluid dynamic models that come under the general category of the moment method or the Chapman-Enskog method have been used for this type of problem. In the present study, on the basis of Eu's generalized hydrodynamics, a computational model for diatomic gases is proposed. The preliminary result indicates that the bulk viscosity plays a considerable role in fundamental flow problems such as the shock structure and shear flow. The general properties of the constitutive equations are obtained through a simple mathematical analysis. With an iterative computational algorithm of the constitutive equations, numerical solutions for the multi-dimensional problem can be obtained.

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Analysis of Two-Dimensional Flow Fields in the Multi-Stage Turbomolecular Pump Using the DSMC Method

  • Heo, Joong-Sik;Hwang, Young-Kyu
    • International Journal of Air-Conditioning and Refrigeration
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    • v.9 no.2
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    • pp.8-18
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    • 2001
  • The direct simulation Monte Carlo Method is applied to investigate the two-dimensional flow fields of a turbomolecular pump(TMP) in both molecular and transition flow regions. The pumping characteristics of the TMP are investigated for a wide range of the Knudsen number. The maximum of compression ratio and of pumping speed strongly depend on the Knudsen number in transition region, while they weakly depend on the Knudsen number in free molecular flow region. The present numerical results show good agreement with the previously known experimental data. Finally. the results of the single blade row in both molecular and transition regions are used to predict the overall performance of a TMP, which has three kinds of blade with 24-rows.

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Plume Behavior Study of Apollo Lunar Module Descent Engine Using Computational Fluid Dynamics (전산유체역학을 이용한 아폴로 달착륙선 하강엔진의 플룸 거동 연구)

  • Choi, Wook;Lee, Kyun Ho;Myong, Rho Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.9
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    • pp.766-774
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    • 2017
  • When a plume flow exhausted from a lunar lander descent engine impinges on the lunar surface, regolith particles on the lunar surface will be dispersed due to a plume-surface interaction. If the dispersed particles collide with the lunar lander, some adverse effects such as a performance degradation can be caused. Thus, this study tried to predict the plume flow behaviors using the CFD methods. A nozzle inside region was analyzed by a continuum flow model based on the Navier-Stokes equations while the plume behaviors of the outside nozzle was performed by comparing and analyzing the individual results using the continuum flow model and the DSMC method. As a result, it was possible to establish an optimum procedure of the plume analysis for the lunar lander descent engine in the vacuum condition. In the future, it is expected to utilize the present results for the development of the Korean lunar lander.

Effect of Vertical Clearance Between a Rotor and Stater of a Disk-Type Drag Pump on the Performance (원판형 드래그펌프 회전자와 고정자 사이의 간극이 성능에 미치는 영향)

  • Kwon, Myoung-Keun;Hwang, Young-Kyu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.12
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    • pp.1501-1510
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    • 2004
  • The pumping characteristics of a single-stage disk-type drag pump (DTDP) are calculated for the variation of the vertical clearance between a rotor and stator by the three-dimensional direct simulation Monte Carlo (DSMC) method. The gas flow mainly belongs to the molecular transition flow region. Spiral channels of a DTDP are cut on the both the upper and lower sides of a rotating disk, but a stationary disk is planar. The interaction between molecules is described by the variable hard-sphere model. The no time counter method is used as a collision sampling technique. The vertical clearance has a significant effect on the pumping performance. Experiments are performed under the outlet pressure range of 0.4∼533 Pa. When the numerical results are compared with the experimental data, the numerical results agree well quantitatively