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