• 제목/요약/키워드: Mach number

검색결과 677건 처리시간 0.023초

저마하수 예조건화 기법을 위한 다중격자 DADI 기법 (Multigrid DADI Method For Low Mach Number Preconditioning Method)

  • 성춘호;권장혁;최윤호;이승수
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2001년도 추계 학술대회논문집
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    • pp.20-30
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    • 2001
  • A multigrid DADI method for low Mach number preconditioning method is presented. The eigenvalues of governing equations are modified by A low Mach number preconditioner developed by Choi & Merkle, and it results in an accurate solution and fast convergence In the low Mach number region. The convergence of numerical method is further accelerated by multigrid method. The efficient and accuracy of present method is shown by comparison with conventional solution method for the compressible flows.

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An Examination on the Singularoty of Grad Moment Equation for Shock Wave Problems

  • 오영기
    • Bulletin of the Korean Chemical Society
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    • 제17권4호
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    • pp.385-390
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    • 1996
  • It has been well known that the Grad thirteen-moment equations have solutions only when the Mach number is less than a limiting value for the stationary plane shock-waves. The limit of Mach number has been re-examined by including successive terms in the series expansion of distribution function. The method employed is the linear analysis of moment equations near up-streaming and down-streaming flows. For the thirteen moment case, it has been confirmed that equations have solutions only when the Mach number is less than 1.6503, which is consistent with the literature value. For the case of twenty moments, the limit of Mach number is decreased to 1.3416.

낮은 Mach수유동 해석을 위한 Preconditioning 가중계수의 의존성 (DEPENDENCE OF WEIGHTING PARAMETER IN PRECONDITIONING METHOD FOR SOLVING LOW MACH NUMBER FLOW)

  • 안영준;신병록
    • 한국전산유체공학회지
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    • 제15권2호
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    • pp.55-61
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    • 2010
  • A dependence of weighting parameter in preconditioning method for solving low Mach number flow with incompressible flow nature is investigated. The present preconditioning method employs a finite-difference method applied Roe‘s flux difference splitting approximation with the MUSCL-TVD scheme and 4th-order Runge-Kutta method in curvilinear coordinates. From the computational results of benchmark flows through a 2-D backward-facing step duct it is confirmed that there exists a suitable value of the weighting parameter for accurate and stable computation. A useful method to determine the weighting parameter is introduced. With this method, high accuracy and stable computational results were obtained for the flow with low Mach number in the range of Mach number less than 0.3.

예조건화 압축성 알고리즘에 의한 저마하수 유동장 해석기법 (Preconditioned Compressible Navier- Stokes Algorithm for Low Mach Number Flows)

  • 고현;윤웅섭
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 1998년도 춘계 학술대회논문집
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    • pp.35-42
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    • 1998
  • Time marching algorithms applied to compressible Navier-Stokes equation have a convergence problem at low Mach number. It is mainly due to the eigenvalue stiffness and pressure singularity as Mach number approaches to zero. Among the several methods to overcome the shortcomings of time marching scheme, time derivative preconditioning method have been used successfully. In this numerical analysis, we adopted a preconditioner of K.H. Chen and developed a two-dimensional, axisymmetric Navier-Stokes program. The steady state driven cavity flow and backward facing step flow problems were computed to confirm the accuracy and the robustness of preconditioned algorithm for low Mach number flows. And the transonic and supersonic flows insice the JPL axisymmetric nozzle internal flow is exampled to investigate the effects of preconditioning at high Mach number flow regime. Test results showed excellent agreement with the experimental data.

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저속 유동 계산의 수렴성 개선을 위한 온도예조건화 II: 나비어스톡스 방정식 (Temperature Preconditioning for Improving Convergence Characteristics in Calculating Low Mach Number Flows, II: Navier-Stokes Equations)

  • 이상현
    • 한국항공우주학회지
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    • 제35권12호
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    • pp.1075-1081
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    • 2007
  • 온도예조건화 방법을 Navier-Stokes 방정식에 적용하여 보았다. 그리고 Navier-Stokes 방정식에 적절한 기준마하수를 결정하기 위해 확산마하수 개념을 도입하였다. 다양한 레이놀즈수에 대한 실린더 주위의 2차원 유동을 계산하였다. 온도예조건화를 Navier-Stokes 방정식에 적용한 결과, 수렴특성이 주목할 만큼 개선되는 것을 보였다. 그리고 확산마하수로 수정한 기준마하수는 국부적으로 마하수가 낮은 영역의 수렴성 문제를 상당히 완화시키는 것을 확인하였다.

직접모사법을 이용한 수직충격파에 관한 연구 (Studies on Normal Shock Waves by Using DSMC)

  • 이동대;박형구;박찬국
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 1995년도 추계 학술대회논문집
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    • pp.241-245
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    • 1995
  • This paper presents the studies on the variation of shape and thickness of a normal shock wave with Mach number and density by using the most useful numerical technique in rarefied gas regime, DSMC(Direct Simulation Monte Carlo). Calculations are peformed for the three different Mach numbers and for one Mach number with different densities. From the obtained results, we find that the shock thickness is decreasing with increasing Mach number, and there are much variations in thickness and shape with decreasing density. Also, there is a noticeable overshoot of the translational temperature near the shock center in the case of a large Mach number.

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잠열 전달이 일어나는 얇은 익형주위의 천음속 습공기 유동에서의 마하수와 익형 두께비의 영향 (THE EFFECTS OF MACH NUMBER AND THICKNESS RATIO OF AIRFOIL ON TRANSONIC FLOW OF MOIST AIR AROUND A THIN AIRFOIL WITH LATENT HEAT TRANSFER)

  • 이장창
    • 한국전산유체공학회지
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    • 제17권4호
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    • pp.93-102
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    • 2012
  • Once the condensation of water vapor in moist air around a thin airfoil occurs, liquid droplets nucleate. The condensation process releases heat to the surrounding gaseous components of moist air and significantly affects their thermodynamic and flow properties. As a results, variations in the aerodynamic performance of airfoils can be found. In the present work, the effects of upstream Mach number and thickness ratio of airfoil on the transonic flow of moist air around a thin airfoil are investigated by numerical analysis. The results shows that a significant condensation occurs as the upstream Mach number is increased at the fixed thickness ratio of airfoil($\epsilon$=0.12) and as the thickness ratio of airfoil is increased at the fixed upstream Mach number($M_{\infty}$=0.80). The condensate mass fraction is also increased and dispersed widely around an airfoil as the upstream Mach number and thickness ratio of airfoil are increased. The position of shock wave for moist air flow move toward the leading edge of airfoil when it is compared with the position of shock wave for dry air.

초음속디퓨져에서 발생하는 수직충격파의 난류경계층의 간섭에 관한 실험 (A New Experiment on Interaction of Normal Shock Wave and Turbulent Boundary Layer in a Supersonic Diffuser)

  • 김희동;홍종우
    • 대한기계학회논문집
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    • 제19권9호
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    • pp.2283-2296
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    • 1995
  • Experiments of normal shock wave/turbulent boundary layer interaction were conducted in a supersonic diffuser. The flow Mach number just upstream of the normal shock wave was in the range of 1.10 to 1.70 and Reynolds number based upon the turbulent boundary layer thickness was varied in the range of 2.2*10$^{[-994]}$ -4.4*10$^{[-994]}$ . The wall pressures in streamwise and spanwise directions were measured for two test cases, in which the turbulent boundary layer thickness incoming into the supersonic diffuser was changed. The results show that the interactions of normal shock wave with turbulent boundary layer in the supersonic diffuser can be divided into three patterns, i.e., transonic interaction, weak interaction and strong interaction, depending on Mach number. The weak interactions generate the post-shock expansion which its strength is strong as the Mach number increases and the strong interactions form the pseudo-shock waves. From the spanwise measurements of wall pressure, it is known that if the flow Mach number is low, the interacting flow fields essentially appear two-dimensional, but they have an apparent 3-dimensionality for the higher Mach numbers.

Analytical and computational analysis of pressure at the nose of a 2D wedge in high speed flow

  • Shaikh, Javed S.;Kumar, Krishna;Pathan, Khizar A.;Khan, Sher A.
    • Advances in aircraft and spacecraft science
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    • 제9권2호
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    • pp.119-130
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    • 2022
  • Supersonic projectiles like rockets, missiles, or aircraft find various applications in the field of defense. The shape of the wings is mainly designed as wedge shape or delta wings for supersonic vehicles. The study of supersonic flows over the wedges and flat plate delta wings around the large scale of incidence angle is considered in the supersonic projectile. In the present paper, the prime attention is to study the pressure at the nose of the plane wedge over the various Mach number and the various angles of incidence. Ghosh piston theory is used to obtain the pressure distribution analytically, and the results are compared with CFD analysis results. The wedge angle and Mach number are the parameters considered for the research work. The range of wedge angle is 50 to 250, and Mach number is 1.5 to 4.0 are considered for the current research work. The analytical results show excellent agreement with the CFD results. The results show that both the parameters wedge angle and Mach number are influential parameters to vary the static pressure. The static pressure increases with an increase in Mach number and wedge angle.

극초음속 쐐기 유동의 Viscous Interaction (Hypersonic Viscous Interaction of Wedge Flows)

  • 김규홍;노오현
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 1996년도 춘계 학술대회논문집
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    • pp.40-45
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    • 1996
  • This paper discribes the viscous interaction of Hypersonic Wedge Flows using Roe FDS and AUSM+. For this purpose we developed the frozen and the equilibrium code and numerically simulated the viscous interaction by changing the surface temperature and the mach number. We used curve fitting data in NASA Reference Publication 1181, 1260 to calculate equilibrium properties. We compare the equilibrium flow with the frozen flow. We conclude that the mach number and the surface temperature are significant parameters, as the surface temperature and the mach number increase the viscous interaction becomes stronger, and we must consider high-temperature effects in hypersonic flow

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