• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.216-217
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• 2008

In recent years, scientific community has found renewed interest in hypersonic flight research. These hypersonic vehicles undergo severe aero-thermal environment during their flight regimes. During reentry and hypersonic flight of these vehicles through atmosphere real gas effects come into play. The analysis of such hypersonic flows is critical for proper aero-thermal design of these vehicles. The numerical simulation of hypersonic real gas flows is a very challenging task. The present work emphasizes numerical simulation of hypersonic flows with thermal non-equilibrium. Hyperbolic system of equations with stiff relaxation method are identified in recent literature as a novel method of predicting long time behaviour of systems such as gas at high temperature. In present work, Energy Relaxation Method (ERM) has been considered to simulate the real gas flows. Navier-Stokes equations A numerical scheme Advection Upstream Splitting Method (AUSM) has been selected. Navier-Stokes solver along with relaxation method has been used for the simulation of real flow over a circular cylinder. Pressure distribution and heat flux over the surface of cylinder has been compared with experiment results of Hannemann. Present heat flux results over the cylinder compared well with experiment. Thus, real gas effects in hypersonic flows can be modeled through energy relaxation method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.27-30
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• 2007

In recent years, scientific community has found renewed interest in hypersonic flight research. These hypersonic vehicles undergo severe aero-thermal environments during their flight regimes. One of the most important topics of research in hypersonic aerodynamics is to find a reasonable way of calculating either the surface temperature or the heat flux to surface when its temperature is held fixed. This requires modeling of physical and chemical processes. Hyperbolic system of equations with stiff relaxation method are being identified in recent literature as a novel method of predicting long time behavior of systems such as gas at high temperatures. In present work, Energy Relaxation Method (ERM) has been considered to simulate the real gas flow over a 2-D cylinder. Present heat flux results over the cylinder compared well with the experiment. Thus, real gas effects in hypersonic flows can be modeled through energy relaxation method.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.328-331
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• 2004

Shock wave boundary layer interactions can make flows around a vehicle be very high pressure and temperature due to pass shock waves in small areas of the hypersonic vehicle. These phenomena can affect a critical problem in the design of hypersonic vehicles. To research the effect of shock wave boundary layer interactions, comer flows were studied in this paper using numerical studies with the NSMB (Navier-Stokes Multi Block) solver and then comparing corresponding numerical results with experimental data of the Huston High Speed Flow Field Workshop II. The mach number of flows is 12.3 in comer flows. The comparison with the computational result is presented based on diverse numerical schemes. Good agreement is obtained.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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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

• Journal of computational fluids engineering
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• v.10 no.3 s.30
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• pp.1-8
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• 2005

In this study, unsteady aerodynamic analyses of a wedge-type airfoil based on nonlinear piston theory and Euler equations have been performed in supersonic and hypersonic flows. The third-order nonlinear piston theory (NPT) to calculate unsteady lift and moment coefficients is derived and applied in the time-domain. Also, unsteady flow quantities are obtained from the two-dimensional time-dependent Euler equations. For the CFD based unsteady aerodynamic analyses, an arbitrary Lagrangean-Eulerian (ALE) formulation for the Euler equations is used to calculate flow fluxes in the computational flow field with moving boundaries. Numerical comparisons for unsteady lift and moment coefficients are presented between NPT and Euler approaches. The results show very good agreements in the high supersonic and hypersonic flows. It means that the present NPT can be efficiently used to predict unsteady aerodynamic forces ol wedge type airfoils with dynamic motions in the high supersonic and hypersonic flow regimes.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.23-28
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• 1999

A mutigrid convergence acceleration technique is presented for computing hypersonic inviscid and viscous flows in equilibrium state. The governing equations are solved using an explicit Runge-Kutta method. Curve fitting data in NASA Reference Publication 1181, 1260 are used to calculate equilibrium properties. In order to ensure stability, damped prolongation and modified implicit residual smoothing are proposed. Blunt body test cases are presented to demonstrate the robustness and the efficiency in performance of the proposed methods

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.311-316
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• 2001

The thin-layer Navier-Stokes equations are solved for the hypersonic flow over blunt cone configurations with applications to laminar as well as turbulent flows. The equations are expressed in the forms of flux-vector splitting and explicit algorithm. The upwind schemes of Steger-Warming and van Leer are investigated in their ability to accurately predict the heating loads along the surface of the body. A comparison with the second order extensions of these schemes is made and a hybrid scheme incorporating a combination of central differencing and flux-vector-splitting is presented. This scheme is also investigated in its ability to accurately predict heat transfer distributions.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.63-70
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• 1999

A Direct simulation Monte-Carlo (DSMC) code is developed, which employs the Monte-Carlo statistical sampling technique to investigate hypersonic rarefied gas flows accompanying chemical reactions. The DSMC method is a numerical simulation technique for analyzing the Boltzmann equation by modeling a real gas flow using a representative set of molecules. Due to the limitations in computational requirements. the present method is applied to a flow around a simple two-dimensional object in exit velocity of 7.6 km/sec at an altitude of 90 km. For the calculation of chemical reactions an air model with five species (O₂, N₂, O, N, NO) and 19 chemical reactions is employed. The simulated result showed various rarefaction effects in the hypersonic flow with chemical reactions.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.12-19
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• 2007

In this study, nonlinear flow-induced vibration(flutter) analyses of a 2-DOF launch vehicle airfoil have been conducted in supersonic and hypersonic flow regimes. Advanced aeroelastic analysis system based on computational fluid dynamics and computational structural dynamics is successfully developed and applied to the present analyses. Nonlinear unsteady aerodynamic analyses considering strong shock wave motions are conducted using inviscid Euler equations. Aeroelastic governing equations for the 2-DOF airfoil system is solved by the coupled integration method with interactive CFD and CSD computation procedures. Typical wedge type airfoil shapes with initial angle-of-attacks are considered to investigate the nonlinear flutter characteristics in supersonic(15). Also, the comparison of detailed aeroelastic responses are practically presented as numerical results.

• 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.