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Update 3.1 Code basics
authored
Jan 09, 2021
by
Udo Ziegler
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@@ -428,15 +428,15 @@ criteria which are
The criterion is applied to primary (or related) physical variables
*U*
( = {𝜚,
**m**
,
*e*
,
**B**
,
*C*
<sub>
*c*
</sub>
}). Undivided first
(
*δ
*
*
U*
) and second (
*δ*
<sup>
2
</sup>
*U*
) differences are
(
*δU*
) and second (
*δ*
<sup>
2
</sup>
*U*
) differences are
computed along various spatial directions. The switch
*α*
∈
\[
0, 1
\]
(code parameter:
`_C.amr_d1`
) selects between a purely
gradient-based criterion (
*α*
=
1) and a purely
gradient-based criterion (
*α*
=
1) and a purely
second-derivatives-based criterion (
*α*
= 0).
*U*
<sub>
*r**e**f*
</sub>
are reference values to avoid division by
zero for indefinite variables. The exponent
*ξ*
∈
\[
0, 2
\]
(code
parameter:
`_C.amr_exp`
) introduces a power law functional on the
grid spacing ratio
*δ
*
*
x*
<sup>
(
*l*
)
</sup>
/
*δ
*
*
x*
<sup>
(0)
</sup>
grid spacing ratio
*δx*
<sup>
(
*l*
)
</sup>
/
*δx*
<sup>
(0)
</sup>
which allows to control the behavior with progressive mesh
refinement. The macro
`FILTER`
(preset to 10
<sup>
− 2
</sup>
) is a
filter to suppress refinement at small-scale solution wiggles. The
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@@ -453,13 +453,11 @@ The criterion is applied to primary (or related) physical variables
flow features right in time.*
-
Jeans-length-based (important in simulations involving selfgravity)
where the first factor is the local Jeans length with
*c*
<sub>
*s*
</sub>
the sound speed and
*G*
the gravitational
constant, and where
*δ
*
*
s*
= min {
*δ
*
*
x*
,
*h*
<sub>
*y*
</sub>
*δ
*
*
y*
,
*h*
<sub>
*z*
</sub>
*δ
*
*
z*
}.
*δs*
= min {
*δx*
,
*h*
<sub>
*y*
</sub>
*δy*
,
*h*
<sub>
*z*
</sub>
*δz*
}.
ℰ
<sub>
*J**e**a**n**s*
</sub>
is a user-specific threshold with the
reciprocal value giving the minimum number of grid cells the local
Jeans length should be resolved.
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