• Title/Summary/Keyword: Nonequilibrium flow

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Time-Dependent Characteristics of the Nonequilibrium Condensation in Subsonic Flows

  • Baek, Seung-Cheol;Kwon, Soon-Bum;Toshiaki Setoguchi;Kim, Heuy-Dong
    • Journal of Mechanical Science and Technology
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    • v.16 no.11
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    • pp.1511-1521
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    • 2002
  • High-speed moist air or steam flow has long been of important subject in engineering and industrial applications. Of many complicated gas dynamics problems involved in moist air flows, the most challenging task is to understand the nonequilibrium condensation phenomenon when the moist air rapidly expands through a flow device. Many theoretical and experimental studies using supersonic wind tunnels have devoted to the understanding of the nonequilibrium condensation flow physics so far. However, the nonequilibrium condensation can be also generated in the subsonic flows induced by the unsteady expansion waves in shock tube. The major flow physics of the nonequilibrium condensation in this application may be different from those obtained in the supersonic wind tunnels. In the current study, the nonequilibrium condensation phenomenon caused by the unsteady expansion waves in a shock tube is analyzed by using the two-dimensional, unsteady, Navier-Stokes equations, which are fully coupled with a droplet growth equation. The third-order TVD MUSCL scheme is applied to solve the governing equation systems. The computational results are compared with the previous experimental data. The time-dependent behavior of nonequilibrium condensation of moist air in shock tube is investigated in details. The results show that the major characteristics of the nonequilibrium condensation phenomenon in shock tube are very different from those in the supersonic wind tunnels.

Numerical Analysis of Nonequilibrium Chemically Reacting Inviscid flow over Blunt-bodies Using Upwind Method (Upwind 방법을 이용한 무딘물체 주위의 화학적 비평형 비점성 유동장의 수치 해석)

  • Seo Jeong Il;Song Dong Joo
    • 한국전산유체공학회:학술대회논문집
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    • 1997.10a
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    • pp.99-105
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    • 1997
  • A finite-difference method based on conservative supra characteristic method type upwind flux difference splitting has been developed to study the nonequilibrium chemically reacting inviscid flow. For nonequilibrium air, NS-1 species equations were strongly coupled with flowfield equations through convection and species production terms. Inviscid nonequilibrium chemically reacting air mixture flows over Blunt-body were solved to demonstrate the capability of the current method. At low altitude flight conditions the nonequilibrium air models predicted almost the same temperature, density and pressure behind the shock as equilibrium flow: however, at high altitudes they showed substantial differences due to nonequilibrium chemistry effect. The new nonequilibrium chemically reacting upwind flux difference splitting mettled can be extended to viscous flow and multi-dimensional flow conditions.

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Rovibrational Nonequilibrium of Nitrogen Behind a Strong Normal Shock Wave

  • Kim, Jae Gang
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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    • pp.28-37
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    • 2017
  • Recent modeling of thermal nonequilibrium processes in simple molecules like hydrogen and nitrogen has indicated that rotational nonequilibrium becomes as important as vibrational nonequilibrium at high temperatures. In the present work, in order to analyze rovibrational nonequilibrium, the rotational mode is separated from the translational-rotational mode that is usually considered as an equilibrium mode in two- and multi-temperature models. Then, the translational, rotational, and electron-electronic-vibrational modes are considered separately in describing the thermochemical nonequilibrium of nitrogen behind a strong normal shock wave. The energy transfer for each energy mode is described by recently evaluated relaxation time parameters including the rotational-to-vibrational energy transfer. One-dimensional post-normal shock flow equations are constructed with these thermochemical models, and post-normal shock flow calculations are performed for the conditions of existing shock-tube experiments. In comparisons with the experimental measurements, it is shown that the present thermochemical model is able to describe the rotational and electron-electronic-vibrational relaxation processes of nitrogen behind a strong shock wave.

CALCULATION OF SHOCK STAND-OFF DISTANCE FOR A SPHERE IN NONEQUILIBRIUM HYPERSONIC FLOW (비평형 극음속 유동에서 구에 대한 충격파 이탈거리 계산)

  • Furudate, M. Ahn
    • Journal of computational fluids engineering
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    • v.17 no.4
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    • pp.69-74
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    • 2012
  • Hypersonic flowfields over a sphere is calculated by using a nonequilibrium flow solver. The flow solver features a two-temperature model and finite rate chemical reaction models to describe nonequilibrium thermochemical processes. For the purpose of validation, the calculated shock stand-off distance is compared with the experimental data which is measured in a ballistic range facility. The present nonequilibrium calculation well reproduced the experimental shock stand-off distance in the cases where the experimental flowfields are expected to be nearly equilibrium, as well as in the cases to be nonequilibrium flowfields in the velocity range 4000 to 5500 m/s.

NUMERICAL METHODS FOR COMPUTATIONS OF NONEQUILIBRIUM HYPERSONIC FLOW AROUND BODIES

  • Park, Tae-Hoon;Kim, Pok-Son
    • Journal of applied mathematics & informatics
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    • v.9 no.1
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    • pp.1-13
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    • 2002
  • In this paper we present numerical methods fur computations of nonequilibrium hypersonic flow of air around bodies including chemical reaction effects and present numerical result of the flow over concave corners. We developed implicit finite difference method to overcome numerical difficulties with the lack of resolution behind the shock and near the body. Using our method we were able to find details of the flow properties near the shock and body and were able to continue the computation of the flow for a long distance from the corner of the body.

Reflections of shocks in nonequilibrium flow of air

  • Park, Tae-Hoon
    • Communications of the Korean Mathematical Society
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    • v.10 no.3
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    • pp.767-781
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    • 1995
  • In this paper we present computation of a reflected shock in the hypersonic flow of air with chemical reactions. We consider two dimensional steady inviscid hypersonic flow of air around bodies including chemical reaction effects. At a high Mach number, a strong shock is formed in front of the body when a wedge is placed against the flow. In front of the shock, temperature and pressure increase greatly and the flow is in nonequilibrium state. If the shock hits a wall, then a reflected shock is formed in the nonequilibrium flow region. Behind this reflected shock, the temperature and pressure are very high. We carry out the computation of the reflected shock and the flow behind it. The jump conditions at the reflected shock are presented. A technique combining smooth transforms of domain and implicit difference methods is used to overcome numerical difficulties associated with the lack of resolution behind the shock and near the body.

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A Passive Control of Interaction of Condensation Shock Wave anc Boundary Layer(I) (응축충격파와 경계층 간섭의 피동제어(I))

  • Choe, Yeong-Sang;Jeong, Yeong-Jun;Gwon, Sun-Beom
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.2
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    • pp.316-328
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    • 1997
  • There were appreciable progresses on the study of shock wave / boundary layer interaction control in the transonic flow without nonequilibrium condensation. But in general, the actual flows associated with those of the airfoil of high speed flight body, the cascade of steam turbine and so on accompany the nonequilibrium condensation, and under a certain circumstance condensation shock wave occurs. Condensation shock wave / boundary layer interaction control is quite different from that of case without condensation, because the droplets generated by the result of nonequilibrium condensation may clog the holes of the porous wall for passive control and the flow interaction mechanism between the droplets and the porous system is concerned in the flow with nonequilibrium condensation. In these connections, it is necessary to study the condensation shock wave / boundary layer interaction control by passive cavity in the flow accompanying nonequilibrium condensation with condensation shock wave. In the present study, experiments were made on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of the porosity, the porous wall area and the depth of cavity on the pressure distribution around condensation shock wave. It was found that the porosity of 12% which was larger than the case of without nonequilibrium condensation produced the largest reduction of pressure fluctuations in the vicinity of condensation shock wave. The results also showed that wider porous area, deeper cavity for the same porosity of 12% are more favourable "passive" effect than the cases of its opposite. opposite.

The Effect of Nonequilibrium Condensation on Shock/Boundary Layer Interaction (비평형응축이 충격파와 경계층의 간섭에 미치는 영향)

  • Kim, H.D.;Lee, K.H.;Setoguchi, T.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.544-549
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    • 2000
  • The effects of nonequilibrium condensation on the shock boundary layer interaction over a transonic bump model were investigated experimentally and numerically. An experiment was conducted using a supersonic indraft wind tunnel. A droplet growth equation was incorporated into two-dimensional Navier-Stokes equation systems. Computations were carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Computations compared with the experimental results. Nonequilibirum condensation suppressed the boundary layer separation and the pressure fluctuations due to the shock boundary layer interaction. Especially the nonequilibrium condensation was helpful to suppress the high frequency components of the pressure fluctuations.

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Effects of Nose Radius of Blunt Body on Aerodynamic Heating in Thermochemical Nonequilibrium Flow (무딘 물체의 노즈 반지름이 비평형 유동의 공력 가열에 미치는 영향)

  • Lee Chang Ho;Park Seung O
    • Journal of computational fluids engineering
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    • v.8 no.4
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    • pp.34-40
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    • 2003
  • The effect of nose radius on aerodynamic heating is investigated by using the Navier-Stokes code extended to thermochemical nonequilibrium airflow, Spherical blunt bodies, whose nose radius varies from 0.O03048 m to 0.6096 m, flying at Mach 25 at an altitude of 53.34 km are considered. Comparison of heat flux at stagnation point with the solution of Viscous Shock Layer and Fay-Riddell are made. Results show that the flow for very small radius is in a nearly frozen state, and therefore the heat flux due to diffusion is smaller than that due to translational energy. As the radius becomes larger, the portion of heat flux by diffusion becomes greater than that of heat flux by translational temperature and approaches to a constant value.

Hypersonic Chemical Nonequilibrium Flow Analysis with HLLE+ and LU-AF (HLLE+와 LU-AF를 이용한 극초음속 화학적 비평형 유동장 해석)

  • Park Soo-Hyung;Kwon Jang Hyuk
    • Journal of computational fluids engineering
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    • v.5 no.2
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    • pp.47-54
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    • 2000
  • A robust Navier-Stokes code has been developed to efficiently predict hypersonic flows in chemical nonequilibrium. The HLLE+ flux discretization scheme is used to improve accuracy and robustness of hypersonic flow analysis. An efficient LU approximate factorization method is also used to solve the flow equations and species continuity equations in fully coupled fashion to implicitly treat stiff source terms of chemical reactions. The HLLE+ scheme shows lower grid dependency for the wall heating rates than other schemes. The developed code has been used to compute chemical nonequilibrium air flow through expanding hypersonic nozzle and past two and three dimensional blunt-nosed bodies. The results are in good agreement with existing numerical and experimental results.

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