A Computational Analysis of Thermochemical Studies in the LENS Facilities

MacLean, Matthew; Holden, Michael; Wadhams, Timothy; Parker, Ronald A.

doi:10.2514/6.2007-121

Cited by 25 publications

(10 citation statements)

References 33 publications

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“…While the inaccuracy of lining up the two images provides only a first-order check of solution quality, it does verify that nothing is dramatically wrong with the simulation. Previous work on CO 2 and some results in the next section show that if the freestream is sufficiently misrepresented, the CFD will predict too small a shock standoff distance. …”

Section: Run 13 Was Made At the Same Nominal Freestream Conditions Bumentioning

confidence: 99%

“…The air at the lowest enthalpy behaves as a perfect gas and it becomes increasingly reactive at the higher enthalpy conditions. The issue of vibrational non-equilibrium has been assessed previously 2 . While the rates according to Millikan and White 11 seem to adequately describe the relaxation process in pure nitrogen, evidence exists that shows that the effective relaxation rate is very much faster when considering mixtures including oxygen 36 .…”

Section: Laminar Forebody Cases In Reacting Airmentioning

confidence: 99%

“…The objective of the work has been principally to (1) validate and understand the operation of the facility at high enthalpy conditions, and (2) to generate a database of reliable measurements with which to assess the current computational modeling capabilities in each of these areas. Some work has been published detailing the analysis and comparison with numerical simulations for certain components of this program 2,3 , but the focus of this work is on the generic spherical capsule tests.…”

Section: Introductionmentioning

confidence: 99%

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Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

MacLean

Mundy

Wadhams

et al. 2008

38th Fluid Dynamics Conference and Exhibit

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A review is presented of ground test experiments of a 146-mm spherical capsule model with forebody and aftbody symmetry plane measurements of heating and pressure for a range of enthalpies and Reynolds numbers to obtain a dataset of fundamental validation data for CFD codes and to develop a database for design-of-experiment of future studies. Comparisons with laminar experiments are made using CFD demonstrating the influence of thermochemical non-equilibrium on the aerodynamic and aerothermal character of the body. For laminar flows in nitrogen up to 10MJ/kg, the good agreement with available measurements suggests that the description of the chemical and thermal activity of the gas is adequate. Analysis of the forebody heating found that a catalytic recombination probability of 0.002 to 0.010 was required to match the measured heat flux. For laminar flows in air up to 14 MJ/kg, some significant differences between CFD and measurements highlight the inadequacy of the current chemical and thermal models to predict the state of the gas after the rapid expansion in the nozzle. Analysis of forebody heating in these cases found that catalytic recombination probability near 1.0 was required to match measured heat flux, suggesting that potentially some type of excitation may be involved that is not properly modeled. Finally, the non-equilibrium excitation may be collision related as limited evidence suggests that the phenomenon becomes more benign as the number of collisions increases.

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Section: Run 13 Was Made At the Same Nominal Freestream Conditions Bumentioning

confidence: 99%

Section: Laminar Forebody Cases In Reacting Airmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

MacLean

Mundy

Wadhams

et al. 2008

38th Fluid Dynamics Conference and Exhibit

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“…However, MacLean et al (2007) show some improvement in the double-cone results with the use of the CVDV model for vibration-dissociation coupling. In any case, it is important to try to rationalize Parker's results with nozzle flow field models.…”

Section: Cubrc Lens-i Nozzle Flow Diagnosticsmentioning

confidence: 99%

Code Validation Studies of High-Enthalpy Flows

Candler¹,

Nompelis²

2006

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Service, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and SS(ES) AFOSRUSAF SUPPLEMENTARY NOTES14. ABSTRACT During the past three years, we have worked to develop and analyze a high-enthalpy flow dataset for CFD code validation. In collaboration with CUBRC Inc. personnel, we designed the experimental conditions for the double-cone geometry used in previous low-enthalpy nitrogen tests. We then used our standard CFD codes and thermo-chemical models to analyze these flows. In general, the comparisons with nitrogen flows are good, even at high enthalpy (1OMJ/kg). But the comparisons between predictions and experiments for air above 5MJ/kg is poor. We find that as the enthalpy increases, the agreement gets worse. In particular, the CFD predicts that the separation zone decreases in size much more rapidly than given in the experiments. There is growing interest in validating existing numerical methods and physical models employed in currently state-of-the-art computational fluid dynamics (CFD) codes. The numerical methods and physical models that are under examination and are the subject of validation studies pertain to the simulation of hypersonic low Reynolds number flows that are in the continuum and the near continuum limit. This work was based on the framework that we established for the validation of numerical methods for inert hypersonic flows under Air Force support in recent years. SUBJECT TERMSIn the past, we simulated experiments of hypersonic laminar double-cone flows that were performed at the Large Energy National Shock (LENS) facility. The experiments were conducted as part of a validation effort for continuum and particle-based codes. The double-cone flow was chosen because it exhibits strong viscous/inviscid and shock interactions, and we have shown that the separation zone that forms at the cone-cone juncture is sensitive to both the amount of numerical dissipation in the numerical scheme and the amount of energy that participates in the dissociation process and other chemical relaxation phenomena (real-gas effects). The double-cone flows are very challenging to compute even with present day computing power. As a result of the previous effort, a large number of experiments were performed in air under high enthalpy conditions. The experiments were performed in different facilities at LENS, and data exists for a range of free-stream Mach and Reynolds numbers at various level of free-stream enthalpy. Simulations of these experiments that employ standard chemical kinetics models show...

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“…The Spalart-Allmaras turbulence model with a compressibility correction is used to model the turbulent boundary layer on the nozzle wall and the simulations show good agreement with test data of Arnold Engineering Development Center Tunnel 9 and Calspan-University of Buffalo Research Center shock-tunnel facilities. Maclean et al [11,12] performed full unsteady Navier-Stokes simulations to study viscous effects in the large energy national shock tunnel facilities.…”

Section: Introductionmentioning

confidence: 99%

Starting Process in a Large-Scale Shock Tunnel

Wang

Liu

et al. 2016

AIAA Journal

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The starting process of the flow in an expansion nozzle (nominal Mach number 6) with an outlet diameter of 1.5 m and 8.9 m length, which is used for a large-scale hypersonic shock tunnel in the Key Laboratory of High-Temperature Gas Dynamics, was simulated and analyzed at incident Mach number M s 3.9. The calculating domains include the driven section (the shock-tube end, about 4.8 m length), the nozzle with about 8.9 m length, and part of the test section (more than 3 m). The characteristics of unsteady nozzle flow, including the shock wave patterns in the nozzle inlet region and inside the nozzle, were analyzed numerically in the viscous and inviscid flow regimes, respectively. The pressure and Mach number results were presented and discussed by comparing with the experimental findings, where the simulated results of the reflected shock wave in the shock tube and the transmitted shock wave inside the nozzle were found to agree well with the test data. Additionally, the case without a contraction section for the throat configuration was also calculated and compared with the case with a contraction section. The effect of the starting flow in these two cases on the flowfield uniformity is discussed in detail in this paper. NomenclatureM s = incident shock Mach number t = time, s

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A Computational Analysis of Thermochemical Studies in the LENS Facilities

Cited by 25 publications

References 33 publications

Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

Code Validation Studies of High-Enthalpy Flows

Starting Process in a Large-Scale Shock Tunnel

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