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Gauge correction to the induction equation for the sake of numerical stability.

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Used in my dynamo work, but apparantly was not done to the main repo.
This commit is contained in:
Miikka Vaisala
2020-09-11 11:58:09 +08:00
parent b7e7853b10
commit 7848dedfbe
1 changed files with 5 additions and 2 deletions
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7
acc/mhd_solver/stencil_kernel.ac
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@@ -449,11 +449,14 @@ induction(in VectorField uu, in VectorField aa)
// yes this actually works. See pg.28 in arXiv:astro-ph/0109497)
// u cross B - AC_eta * AC_mu0 * (AC_mu0^-1 * [- laplace A + grad div A ])
const Vector B = curl(aa);
const Vector grad_div = gradient_of_divergence(aa);
//MV: Due to gauge freedom we can reduce the gradient of scalar (divergence) from the equation
//const Vector grad_div = gradient_of_divergence(aa);
const Vector lap = laplace_vec(aa);
// Note, AC_mu0 is cancelled out
const Vector ind = cross(value(uu), B) - AC_eta * (grad_div - lap);
//MV: Due to gauge freedom we can reduce the gradient of scalar (divergence) from the equation
//const Vector ind = cross(value(uu), B) - AC_eta * (grad_div - lap);
const Vector ind = cross(value(uu), B) + AC_eta * lap;
return ind;
}