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| Titel |
Anelastic Versus Fully Compressible Turbulent Convection |
| VerfasserIn |
Jan Verhoeven, Thomas Wiesehöfer, Stephan Stellmach |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113976
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| Publikation (Nr.) |
 EGU/EGU2015-14226.pdf |
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| Zusammenfassung |
| Numerical simulations of turbulent convection in an ideal gas, using either the anelastic
approximation—widely used for modeling dynamos in gas giants—or the fully
compressible equations, are compared. Theoretically, the anelastic approximation is
expected to hold in weakly superadiabatic systems with ε = δT/Tr ≈ª 1, where δT
denotes the superadiabatic temperature drop over the convective layer and Tr the
bottom temperature. Using direct numerical simulations in a plane layer geometry, a
detailed comparison of anelastic and fully compressible convection is carried out.
With decreasing superadiabaticity ε, the fully compressible results are found to
converge linearly to the anelastic solution with larger density contrasts generally
improving the match. We conclude that in many solar and planetary applications,
where the superadiabaticity is expected to be vanishingly small, results obtained
with the anelastic approximation are in fact more accurate than fully compressible
computations, which typically fail to reach small ε for numerical reasons. On the other hand,
if the astrophysical system studied contains ε ~ O(1) regions, such as the solar
photosphere, fully compressible simulations have the advantage of capturing the full
physics. Interestingly, even in weakly superadiabatic regions, like the bulk of the
solar convection zone, the errors introduced by using artificially large values for ε
for efficiency reasons remain moderate. If quantitative errors of the order of 10%
are acceptable in such low ε regions, our work suggests that fully compressible
simulations can indeed be computationally more efficient than their anelastic counterparts. |
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