• Title/Summary/Keyword: State equation

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IMMERSED BOUNDARY METHOD FOR COMPRESSIBLE VISCOUS FLOW AROUND MOVING BODIES (이동하는 물체 주위의 압축성 유동에 대한 가상경계법)

  • Cho, Yong;Chopra, Jogesh;Morris, Philip J.
    • Journal of computational fluids engineering
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    • v.13 no.3
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    • pp.35-43
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    • 2008
  • A methodology for the simulation of compressible high Reynolds number flow over rigid and moving bodies on a structured Cartesian grid is described in this paper. The approach is based on a modified version of the Brinkman Penalization method. To avoid oscillations in the vicinity of the body and to simulate shcok-containing flows, a Weighted Essentially Non-Oscillatory scheme is used to discretize the spatial flux derivatives. For high Reynolds number viscous flow, two turbulence models of the two-equation Menter's SST URANS model and a two-equation Detached Eddy Simulation are implemented. Some simple flow examples are given to assess the accuracy of the technique. Finally, a moving grid capability is demonstrated.

Optimal Control for Proximity Operations and Docking

  • Lee, Dae-Ro;Pernicka, Henry
    • International Journal of Aeronautical and Space Sciences
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    • v.11 no.3
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    • pp.206-220
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    • 2010
  • This paper proposes optimal control techniques for determining translational and rotational maneuvers that facilitate proximity operations and docking. Two candidate controllers that provide translational motion are compared. A state-dependent Riccati equation controller is formulated from nonlinear relative motion dynamics, and a linear quadratic tracking controller is formulated from linearized relative motion. A linear quadratic Gaussian controller using star trackers to provide quaternion measurements is designed for precision attitude maneuvering. The attitude maneuvers are evaluated for different final axis alignment geometries that depend on the approach distance. A six degrees-of-freedom simulation demonstrates that the controllers successfully perform proximity operations that meet the conditions for docking.

An Optimal PI Controller Tuning for TITO System (TITO시스템의 최적 PI제어기 동조)

  • Um, Tae-Ho;Suh, Byung-Suhl
    • Proceedings of the KIEE Conference
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    • 2003.04a
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    • pp.186-189
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    • 2003
  • This paper presents an optimal tuning method of the decentralized PI controller of two-input, two-output(TITO) second order system to be formulated as LQR. The tuning method of proposed decentralized PI controller is developed by establishing the relationships between the closed-loop state equation including decentralized PI control factors and the closed-loop state equation of LQR, which can be guaranteed the performance and stability-robustness by selecting the weighting factors Q and R of the cost function in order to satisfy design specifications in frequency domain.

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Real gas equation of state and upwind scheme (실제기체 상태방정식과 풍상차분기법)

  • Choi Jeong-Yeol;Kim Chin-Su;Oh Se-Jong
    • 한국전산유체공학회:학술대회논문집
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    • 2000.05a
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    • pp.153-158
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    • 2000
  • For the analysis of compressible flow with real gas effect, characteristic form of Roe's Riemann solver was derived again using real gas equation of state and variable specific heal and it was extended to multi component reactive system. From this study, it is known that some correction should be made for the use of existing numerical algorithm. 1) Sonic speed and characteristic variable should be corrected with real gas effect. 2) Roe's average was applicable only with the assumption of constant properties. 3) Artificial damping term and characteristic variables should be corrected but their influence may not be significant.

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Theoretical Analysis of Steady State Low Current Arcs in Dual Flow Nozzles

  • Song, K.D.;Shin, Y.J.;Lee, H.S.;Kim, K.S.
    • Proceedings of the KIEE Conference
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    • 1992.07b
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    • pp.952-957
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    • 1992
  • When the circuit-breaker switches off, an electric arc is established between the contacts. It is very important to understand the arc characteristics for the design of a circuit breaker. This article describes the theoretical analysis of the arc characteristics by means of energy integral method when convection dominated low current arcs are produced in the dual-airflow nozzle of a model interrupter. In order to investigate the arc radius, the average electric field strength and the arc voltage, the arc column is divided into two regions, and then the energy conservation equation is applied to the arc in each region together with the axial cold flow mass flux function, steady-state mass balance equation and Ohm's law. The results show good agreements with those of other researchers.

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Ionization and Attachment Coefficients in Mixtures of $SF_6$ and $N_2$ ($SF_6-N_2$ 혼합기체(混合氣體)의 전리(電離) 및 부착계수(附着係數))

  • Kim, Sang-Nam
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.1
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    • pp.44-47
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    • 2009
  • This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. $SF_6$ gas is widely used in industrial of insulation field. In this paper, $N_2$ is mixed to improve pure $SF_6$ gas characteristics. Electron transport coefficients in $SF_6-N_2$ mixture gases are simulated in range of E/N values from 70 to 400 [Td] at 300K and 1 Torr by using Boltzmann equation method. The results of this method. which are ionization coefficient, attachment coefficient, effective ionization coefficient, and critical E/N, can be important data to present characteristic of gas for insulation. Specially critical E/N is a data to evaluate insulation strength of a gas and is presented in this paper for various mixture ratios of $SF_6-N_2$ mixture gases.

Application of the BWRS equation of state of polar halocarbons (극성 할로겐 탄화수소 화합물 물성 예측에 BWRS 상태 방정식의 응용)

  • 이태종;김부웅
    • Journal of Energy Engineering
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    • v.2 no.3
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    • pp.315-322
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    • 1993
  • The generalized 23 constants of the Benedict-Webb-Rubin-Starling (BWRS) equation of state were modified to achieve accurate predictions of thermo-physical properties for polar halocarbons. Multiproperty analysis was employed to obtain an optimum set of 23 constants for individual halocarbons. The overall average absolute deviations of predicted properties for those halocarbons using the 23 constants optimized for each halocarbon with use of either an acentric factor or orientation parameters are 0.41% for density, 0.33 Kcal/kg for enthalpy and 0.39% for vapor pressure. These results show a remarkable improvement in predicting properties over the ones obtained by use of the generalized constants for all the ten halocarbons tested here.

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Application of the Modified Reactive SPH Method for Simulating Explosions

  • Sirotkin, Fedir V.;Yoh, Jai-Ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.922-925
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    • 2011
  • Smoothed Particle Hydrodynamics (SPH) is a Lagrangian method widely used for the modeling fluid flows. Simulations of explosions require, besides the hydrodynamic equations, a realistic equation of state, an energy source term, and a set of chemical kinetic equations to follow the composition changes of the gas during the explosion. The performance of the hydrodynamic equations is investigated in the framework of the Sedov-Taylor blast-wave. The implementation of chemical kinetic equations and equation of state is studied with 1D detonation of TNT slab. Our results are compared to those from analytical and experimental studies.

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Effects of Swirl number and Recess length on Flame Structure of Supercritical Kerosene/LOx Double Swirl Coaxial Injector (선회수와 리세스 길이가 초임계상태 케로신/액체산소 이중 와류 동축형 분사기의 화염구조에 미치는 영향 해석)

  • Park, Sangwoon;Kim, Taehoon;Kim, Yongmo
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.33-35
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    • 2012
  • This study has been mainly motivated to numerically model the supercritical mixing and combustion processes encountered in the liquid propellant rocket engines. In the present approach, turbulence is represented by the extended k-e model. To account for the real fluid effects, the propellant mixture properties are calculated by using generalized cubic equation of state. In order to realistically represent the turbulence-chemistry interaction in the turbulent nonpremixed flames, the flamelet approach based on the real fluid flamelet library has been adopted. Based on numerical results, the detailed discussions are made for the effects of swirl number on flame structure of supercritical kerosene/LOx double swirl coaxial injector.

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Investigation of vapor-liquid equilibrium of HFC125/134a system (HFC125/134a계의 기-액상평형에 관한 연구)

  • 김창년;박영무
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.10 no.2
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    • pp.238-250
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    • 1998
  • Vapor-liquid equilibrium apparatus is designed and set up. The vapor-liquid equilibrium data of the binary system HFC125/134a are measured in the range between 268.15 and 283.15K at five compositions. Twenty-five equilibrium data are obtained. To verify consistency of these data, they are tested for thermodynamic consistency. Based upon the present data, the binary interaction parameter for CSD and RKS equation of state is calculated at five isotherms and comparison with the data in the open literatures is made. Results of Nagel and Bier are in very good agreements with those from this study within 0.32∼1.11% for bubble point pressure and -0.66∼0.18% for vapor mole fraction.

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