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  • 1
    Electronic Resource
    Electronic Resource
    Computational study of reacting flow establishment in expansion tube facilities (1997)
    Springer
    Shock waves 7 (1997), S. 335-342 
    Details
    ISSN: 1432-2153
    Keywords: Key words:Hypersonic flow, Shock induced combustion, Unsteady combustion, Detailed chemistry, Ram accelerator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract. We study the temporal evolution of the combustion flowfield established by the interaction of ram accelerator-type projectiles with an explosive gas mixture accelerated to hypersonic speeds in an expansion tube. The Navier-Stokes equations for a chemically reacting gas mixture are solved in a fully coupled manner using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order, total variation diminishing scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen-argon chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of expansion tube flowfields are then presented for two different geometries: an axisymmetric projectile and a ram accelerator configuration. The development of the shock-induced combustion process is followed. The temporal variations of the calculated thrust and drag forces on the ram accelerator projectile are also presented. In the axisymmetric projectile case, which was designed to ensure combustion only in the boundary layer, the radial extent of the flame front during the initial transient phase was surprisingly large. In the ram accelerator configuration the flame propagated upstream along both the projectile and tube wall boundary layers, resulting in unstart.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001930050088
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    Paper (German National Licenses)
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  • 2
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    Structure and stability of one-dimensional detonationsin ethylene-air mixtures (2005)
    Springer
    Details
    Publication Date: 2005-06-01
    Print ISSN: 0938-1287
    Electronic ISSN: 1432-2153
    Topics: Physics , Technology
    Published by Springer
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    PAPER CURRENT
  • 3
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    Computational study of reacting flow establishment in expansion tube facilities (1997)
    Springer
    Details
    Publication Date: 1997-12-01
    Print ISSN: 0938-1287
    Electronic ISSN: 1432-2153
    Topics: Physics , Technology
    Published by Springer
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    PAPER CURRENT
  • 4
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    Simulation of unsteady hypersonic combustion around projectiles in an expansion tube (2001)
    Springer
    Details
    Publication Date: 2001-09-01
    Print ISSN: 0938-1287
    Electronic ISSN: 1432-2153
    Topics: Physics , Technology
    Published by Springer
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    PAPER CURRENT
  • 5
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    Compressible flow past a contour and stationary vortices (1987)
    Cambridge University Press
    Details
    Publication Date: 1987-05-01
    Description: The Rayleigh-Janzen expansion method is extended to plane and steady flows which contain one or more point vortices interacting with a smooth or sharp-edged obstacle. A uniformly valid approximate solution of the compressible-flow equations is deduced by applying a perturbation method and by using matched asymptotic expansions to solve the resulting singular perturbation problem. The method yields compressibility corrections for the vortex positions and for the velocities. Results are presented for the flow past a circle and a pair of symmetric vortices (Foppl's flow). They show that the compressibility effects are substantial and are consistent with experimental data. © 1987, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 6
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    Computational Analysis for Rocket-Based Combined-Cycle Systems During Rocket-Only Operation (2000)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A series of Reynolds-averaged Navier-Stokes calculations were employed to study the performance of rocket-based combined-cycle systems operating in an all-rocket mode. This parametric series of calculations were executed within a statistical framework, commonly known as design of experiments. The parametric design space included four geometric and two flowfield variables set at three levels each, for a total of 729 possible combinations. A D-optimal design strategy was selected. It required that only 36 separate computational fluid dynamics (CFD) solutions be performed to develop a full response surface model, which quantified the linear, bilinear, and curvilinear effects of the six experimental variables. The axisymmetric, Reynolds-averaged Navier-Stokes simulations were executed with the NPARC v3.0 code. The response used in the statistical analysis was created from Isp efficiency data integrated from the 36 CFD simulations. The influence of turbulence modeling was analyzed by using both one- and two-equation models. Careful attention was also given to quantify the influence of mesh dependence, iterative convergence, and artificial viscosity upon the resulting statistical model. Thirteen statistically significant effects were observed to have an influence on rocket-based combined-cycle nozzle performance. It was apparent that the free-expansion process, directly downstream of the rocket nozzle, can influence the Isp efficiency. Numerical schlieren images and particle traces have been used to further understand the physical phenomena behind several of the statistically significant results.
    Keywords: Spacecraft Propulsion and Power
    Type: Journal of Propulsion and Power; Volume 16; No. 6; 1030-1039
    Format: application/pdf
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  • 7
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    Computational Study of Flow Establishment in a Ram Accelerator (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The temporal evolution of the combustion process established during projectile transition from the launch tube into the ram accelerator section containing an explosive hydrogen-oxygen-argon gas mixture is studied. The Navier-Stokes equations for chemically reacting flow are solved in a fully coupled manner, using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order total variation diminishing scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of two ram accelerator configurations are then presented. In particular, the temporal developments of shock-induced combustion and thrust forces are followed. Positive thrust is established in both cases; however, in one of the ram accelerator configurations studied, combustion in the boundary layer enhances its separation, ultimately resulting in unstart.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-107068 , NAS 1.15:107068 , E-9931 , ICOMP-95-20 , AIAA PAPER 95-2489 , NIPS-95-06486
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  • 8
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    Simulation of Unsteady Hypersonic Combustion Around Projectiles in an Expansion Tube (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The temporal evolution of combustion flowfields established by the interaction between wedge-shaped bodies and explosive hydrogen-oxygen-nitrogen mixtures accelerated to hypersonic speeds in an expansion tube is investigated. The analysis is carried out using a fully implicit, time-accurate, computational fluid dynamics code that we developed recently for solving the Navier-Stokes equations for a chemically reacting gas mixture. The numerical results are compared with experimental data from the Stanford University expansion tube for two different gas mixtures at Mach numbers of 4.2 and 5.2. The experimental work showed that flow unstart occurred for the Mach 4.2 cases. These results are reproduced by our numerical simulations and, more significantly, the causes for unstart are explained. For the Mach 5.2 mixtures, the experiments and numerical simulations both produced stable combustion. However, the computations indicate that in one case the experimental data were obtained during the transient phase of the flow; that is, before steady state had been attained.
    Keywords: Fluid Mechanics and Heat Transfer
    Type: NASA/CR-1999-209304 , AIAA Paper 99-2640 , NAS 1.26:209304 , ICOMP-99-06 , E-11825 , Joint Propulsion; Jun 20, 1999 - Jun 24, 1999; Los Angeles, CA; United States
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  • 9
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    Computational Study of Flow Establishment in Hypersonic Pulse Facilities (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents a study of the temporal evolution of the combustion flowfield established by the interaction of ram-accelerator-type projectiles with an explosive gas mixture accelerated to hypersonic speeds in an expansion tube. The Navier-Stokes equations for a chemically reacting gas are solved in a fully coupled manner using an implicit, time accurate algorithm. The solution procedure is based on a spatially second order, total variation diminishing (TVD) scheme and a temporally second order, variable-step, backward differentiation formula method. The hydrogen-oxygen chemistry is modeled with a 9-species, 19-step mechanism. The accuracy of the solution method is first demonstrated by several benchmark calculations. Numerical simulations of expansion tube flowfields are then presented for two different configurations. In particular, the development of the shock-induced combustion process is followed. In one case, designed to ensure ignition only in the boundary layer, the lateral extent of the combustion front during the initial transient phase was surprisingly large. The time histories of the calculated thrust and drag forces on the ram accelerator projectile are also presented.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-CR-198407 , NAS 1.26:198407 , E-9930 , ICOMP-95-19 , NIPS-96-07535 , International Workshop on Ram Accelerators; Jul 17, 1995 - Jul 20, 1995; Seattle, WA; United States
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  • 10
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    Structure and Stability of One-Dimensional Detonations in Ethylene-Air Mixtures (2003)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The propagation of one-dimensional detonations in ethylene-air mixtures is investigated numerically by solving the one-dimensional Euler equations with detailed finite-rate chemistry. The numerical method is based on a second-order spatially accurate total-variation-diminishing scheme and a point implicit, first-order-accurate, time marching algorithm. The ethylene-air combustion is modeled with a 20-species, 36-step reaction mechanism. A multi-level, dynamically adaptive grid is utilized, in order to resolve the structure of the detonation. Parametric studies over an equivalence ratio range of 0.5 less than phi less than 3 for different initial pressures and degrees of detonation overdrive demonstrate that the detonation is unstable for low degrees of overdrive, but the dynamics of wave propagation varies with fuel-air equivalence ratio. For equivalence ratios less than approximately 1.2 the detonation exhibits a short-period oscillatory mode, characterized by high-frequency, low-amplitude waves. Richer mixtures (phi greater than 1.2) exhibit a low-frequency mode that includes large fluctuations in the detonation wave speed; that is, a galloping propagation mode is established. At high degrees of overdrive, stable detonation wave propagation is obtained. A modified McVey-Toong short-period wave-interaction theory is in excellent agreement with the numerical simulations.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2003-212586 , AIAA Paper 2003-4248 , E-14143 , 33rd Fluid Dynamics Conference and Exhibit; Jun 23, 2003 - Jun 26, 2003; Orlando, FL; United States
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