167 research outputs found
Comparison of Coupled Radiative Flow Solutions with Project Fire 2 Flight Data
A nonequilibrium, axisymmetric, Navier-Stokes flow solver with coupled radiation has been developed for use in the design or thermal protection systems for vehicles where radiation effects are important. The present method has been compared with an existing now and radiation solver and with the Project Fire 2 experimental data. Good agreement has been obtained over the entire Fire 2 trajectory with the experimentally determined values of the stagnation radiation intensity in the 0.2-6.2 eV range and with the total stagnation heating. The effects of a number of flow models are examined to determine which combination of physical models produces the best agreement with the experimental data. These models include radiation coupling, multitemperature thermal models, and finite rate chemistry. Finally, the computational efficiency of the present model is evaluated. The radiation properties model developed for this study is shown to offer significant computational savings compared to existing codes
Carbon Dioxide Injection for Hypervelocity Boundary Layer Stability
An approach for introducing carbon dioxide as a means or stabilizing a hypervelocity boundary layer over a slender bodied vehicle is investigated through the use of numerical simulations. In the current study, two different test bodies are examined. The first is a five-degree-half-angle cone currently under research at the GALCIT T5 Shock Tunnel with a 4 cm porous wall insert used to transpire gas into the boundary layer. The second test body is a similar cone with a porous wall over a majority of cone surface. Computationally, the transpiration is performed using an axi-symmetric flow simulation with wall-normal blowing. The effect of the injection and the transition location are gauged by solving the parabolized stability equations and using the semi-empirical e^N method. The results show transition due to the injection for the first test body and a delay in the transition location for the second test body as compared to a cone without injection under the same flight conditions. The mechanism for the stabilizing effect of carbon dioxide is also explored through selectively applying non-equilibrium processes to the stability analysis. The results show that vibrational non-equilibrium plays a role in reducing disturbance amplification; however, other factors also contribute
Evaluation of Hypervelocity Carbon Dioxide Blunt Body Experiments in an Expansion Tube Facility
This work represents efforts to study high-enthalpy carbon dioxide flows in anticipation
of the upcoming Mars Science Laboratory (MSL) and future missions. The
current study extends the previous presentation of experimental results by the comparison
now with axisymmetric simulations incorporating detailed thermochemical
modeling. The work is motivated by observed anomalies between experimental
and numerical studies in hypervelocity impulse facilities. In this work, experiments
are conducted in the Hypervelocity Expansion Tube (HET) which, by virtue of its
flow acceleration process, exhibits minimal freestream dissociation in comparison
to reflected shock tunnels. This simplifies the comparison with computational result
as freestream dissociation and considerable thermochemical excitation can be
neglected. Shock shapes of the Laboratory aeroshell and spherical geometries are
compared with numerical simulations. In an effort to address surface chemistry
issues arising from high-enthalpy carbon dioxide ground-test based experiments,
spherical stagnation point and aeroshell heat transfer distributions are also compared
with simulation. The shock stand-off distance has been identified in the
past as sensitive to the thermochemical state and as such, is used here as an experimental
measureable for comparison with CFD and two different theoretical
models. For low-density, small-scale experiments it is seen that models based upon
assumptions of large binary scaling values are unable to match the experimental
and numerical results. Very good agreement between experiment and CFD is seen
for all shock shapes and heat transfer distributions fall within the non-catalytic and
super-catalytic solutions
Experimental and Numerical Investigation of Hypervelocity Carbon Dioxide Flow over Blunt Bodies
This paper represents ongoing efforts to study high-enthalpy carbon dioxide flows in anticipation of the upcoming
Mars Science Laboratory and future missions. The work is motivated by observed anomalies between experimental
and numerical studies in hypervelocity impulse facilities. In this study, experiments are conducted in the
hypervelocity expansion tube that, by virtue of its flow acceleration process, exhibits minimal freestream dissociation
in comparison with reflected shock tunnels, simplifying comparison with simulations. Shock shapes of the laboratory
aeroshell at angles of attack of 0, 11, and 16 deg and spherical geometries are in very good agreement with simulations
incorporating detailed thermochemical modeling. Laboratory shock shapes at a 0 deg of attack are also in good
agreement with data from the LENS X expansion tunnel facility, confirming results are facility-independent for the
same type of flow acceleration. The shock standoff distance is sensitive to the thermochemical state and is used as an
experimental measurable for comparison with simulations and two different theoretical models. For low-density
small-scale experiments, it is seen that models based upon assumptions of large binary scaling values do not match the
experimental and numerical results. In an effort to address surface chemistry issues arising in high-enthalpy groundtest
experiments, spherical stagnation point and aeroshell heat transfer distributions are also compared with the
simulation. Heat transfer distributions over the aeroshell at the three angles of attack are in reasonable agreement
with simulations, and the data fall within the noncatalytic and supercatalytic solutions
Interaction of Chemistry, Turbulence, and Shock Waves in Hypervelocity Flow
Significant progress was made in the third year of an interdisciplinary experimental, numerical and theoretical program to extend the state of knowledge
and understanding of the effects of chemical reactions in hypervelocity flows. The program addressed the key problems in aerothermochemistry that arise from.the interaction between the three strongly nonlinear effects:
Compressibility; vorticity; and chemistry. Important new results included:
• New data on transition in hypervelocity carbon dioxide flows
• New method of free-piston shock tunnel operation for lower enthalpy
• Accurate new method for computation of self-similar flows
• New experimental data on flap-induced separation at high enthalpy
• Insight into mechanisms active in reacting shear layers from comparison of experiment and computation
• Extensive new data from Rayleigh scattering diagnostics of supersonic shear layer
• Comparison of new experiments and computation of hypervelocity double-wedge flow yielded important differences
• Further first-principles computations of electron collision cross-sections of CO, N_2 and NO
• Good agreement between EFMO computation and experiment of flow over a cone at high incidence
• Extension of LITA diagnostics to high temperature
Carbon Dioxide Injection for Hypervelocity Boundary Layer Stability
An approach for introducing carbon dioxide as a means or stabilizing a hypervelocity boundary layer over a slender bodied vehicle is investigated through the use of numerical simulations. In the current study, two different test bodies are examined. The first is a five-degree-half-angle cone currently under research at the GALCIT T5 Shock Tunnel with a 4 cm porous wall insert used to transpire gas into the boundary layer. The second test body is a similar cone with a porous wall over a majority of cone surface. Computationally, the transpiration is performed using an axi-symmetric flow simulation with wall-normal blowing. The effect of the injection and the transition location are gauged by solving the parabolized stability equations and using the semi-empirical e^N method. The results show transition due to the injection for the first test body and a delay in the transition location for the second test body as compared to a cone without injection under the same flight conditions. The mechanism for the stabilizing effect of carbon dioxide is also explored through selectively applying non-equilibrium processes to the stability analysis. The results show that vibrational non-equilibrium plays a role in reducing disturbance amplification; however, other factors also contribute
Electromagnetic Reduction of Plasma Density During Atmospheric Reentry and Hypersonic Flights
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76341/1/AIAA-32147-259.pd
Spectroscopic Measurements in the Shock Relaxation Region of a Hypervelocity Mach Reflection
We examine the spatial temperature profile in the non-equilibrium relaxation region
behind a stationary shock wave. The normal shock wave is established through a Mach
reflection configuration from an opposing wedge arrangement for a hypervelocity air Mach
7.42 freestream. Schlieren images confirm that the shock configuration is steady and the
location is repeatable. Emission spectroscopy is used to identify dissociated species and to
obtain vibrational temperature measurements using the NO and OH A-X band sequences.
Temperature measurements are presented at selected locations behind the normal shock.
LIFBASE is used as the simulation spectrum software for OH temperature-fitting, however the need to access higher vibrational and rotational levels for NO leads to the use of
an in-house developed algorithm. For NO, results demonstrate the contribution of higher
vibrational and rotational levels to the spectra at the conditions of this study. Very good
agreement is achieved between the experimentally measured NO vibrational temperatures
and calculations performed using a state-resolved, one-dimensional forced harmonic oscillator thermochemical model
Simulation of Ablating Hypersonic Vehicles with Finite-Rate Surface Chemistry
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140434/1/6.2014-2124.pd
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