| Issue |
A&A
Volume 488, Number 1, September II 2008
|
|
|---|---|---|
| Page(s) | 9 - 23 | |
| Section | Astrophysical processes | |
| DOI | https://doi.org/10.1051/0004-6361:20079098 | |
| Published online | 24 June 2008 | |
Lambda effect from forced turbulence simulations*
1
Observatory, PO Box 14, 00014 University of Helsinki, Finland e-mail: petri.kapyla@helsinki.fi
2
NORDITA, AlbaNova University Center, Roslagstullsbacken 23, 10691 Stockholm, Sweden
Received:
19
November
2007
Accepted:
22
May
2008
Aims. We determine the components of the Λ-effect tensor that quantifies the contributions to the turbulent momentum transport even for uniform rotation.
Methods. Three-dimensional numerical simulations are used to study turbulent transport in triply periodic cubes under the influence of rotation and anisotropic forcing. Comparison is made with analytical results obtained via the so-called minimal tau-approximation.
Results. In the case where the turbulence intensity in the vertical
direction dominates, the vertical stress is always negative.
This situation is expected to occur in stellar convection zones.
The horizontal component of the stress
is weaker and exhibits a maximum at latitude 
– regardless of how rapid
the rotation is. The minimal tau-approximation captures many of the
qualitative features of the numerical results, provided the relaxation
time tau is close to the turnover time, i.e. the Strouhal
number is of order unity.
Key words: hydrodynamics / turbulence / Sun: rotation / stars: rotation
© ESO, 2008
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