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Radiative Heating of Large Meteoroids During Atmospheric EntryA high-fidelity approach for simulating the aerothermodynamic environments of meteor entries was developed, which allows the commonly assumed heat transfer coefficient of 0.1 to be assessed. This model uses chemically reacting computational fluid dynamics (CFD), coupled with radiation transport and surface ablation. Coupled radiation accounts for the impact of radiation on the flowfield energy equations, while coupled ablation explicitly models the injection of ablation products within the flowfield and radiation simulations. For a meteoroid with a velocity of 20 km/s, coupled radiation is shown to reduce the stagnation point radiative heating by over 60%. The impact of coupled ablation (with coupled radiation) is shown to provide at least a 70% reduction in the radiative heating relative to cases with only coupled radiation. This large reduction is partially the result of the low ionization energies of meteoric ablation products relative to air species. The low ionization energies of ablation products, such as Mg and Ca, provide strong photoionization and atomic line absorption in regions of the spectrum that air species do not. MgO and CaO are also shown to provide significant absorption. Turbulence is shown to impact the distribution of ablation products through the shock-layer, which results in up to a 100% increase in the radiative heating downstream of the stagnation point. To create a database of heat transfer coefficients, the developed model was applied to a range of cases. This database considered velocities ranging from 14 to 20 km/s, altitudes ranging from 20 to 50 km, and nose radii ranging from 1 to 100 m. The heat transfer coefficients from these simulations are below 0.045 for the range of cases, for both laminar and turbulent, which is significantly lower than the canonical value of 0:1. When the new heat transfer model is applied to a Tunguska-like 15 Mt entry, the effect of the new model is to lower the height of burst by up to 2 km, depending on assumed entry angle. This, in turn, results in a significantly larger ground damage footprint than when the canonical heating assumption is used.
Document ID
20190025958
Acquisition Source
Langley Research Center
Document Type
Accepted Manuscript (Version with final changes)
Authors
Christopher O Johnston (Langley Research Center Hampton, Virginia, United States)
Eric C Stern (Ames Research Center Mountain View, California, United States)
Lorien F Wheeler (Ames Research Center Mountain View, California, United States)
Date Acquired
June 14, 2019
Publication Date
February 21, 2018
Publication Information
Publication: Icarus
Publisher: Elsevier
Volume: 309
Issue Publication Date: July 15, 2018
ISSN: 0019-1035
DOI: doi:10.1016/j.icarus.2018.02.026
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
NF1676L-28086
Distribution Limits
Public
Copyright
Public Use Permitted.

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