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<p>Hello,</p>
<p>Thank you for your answers, they were really helpful.</p>
<p>Regards,<br>
</p>
<div class="moz-cite-prefix">On 29/10/19 14:41, Eddie Hansen wrote:<br>
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<div dir="ltr">In general, here is how periodic boundaries
work...
<div><br>
</div>
<div>Just consider the x-direction and say you are using
xl_boundary_type = "periodic" and xr_boundary_type =
"periodic". Let's number the cells starting at n and going up
to m, so we have n, n+1, n+2, ... , m-1, m. The "guard cells"
are those cells outside the domain to the left of n and to the
right of m. With periodic conditions, the values of guard cell
n-1 are set to the values of the interior cell m. Likewise,
values of guard cell m+1 are set to values of interior cell n.
Depending on the solver order, more guard cells will be filled
accordingly. For example, the values of guard cell n-2 are set
to values of interior cell m-1, and so on.</div>
<div><br>
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<div>This effectively makes any flux on the right boundary equal
to the flux on the left boundary. In other words, if material
leaves the grid on the right, it will enter on the left, and
vice-versa. You can think of it as "wrapping around".</div>
<div><br>
</div>
<div>Hopefully that answers your question about periodic
boundary conditions. To do something like keep a constant
magnetic field value at a boundary, you have to implement a
user-defined boundary like Ryan mentioned.</div>
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<br>
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<div dir="ltr" class="gmail_attr">On Tue, Oct 29, 2019 at 3:13
PM Ryan Farber <<a href="mailto:rjfarber@umich.edu"
moz-do-not-send="true">rjfarber@umich.edu</a>> wrote:<br>
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<div dir="ltr">Hi Guido,
<div><br>
</div>
<div>I'm not sure how periodic boundary conditions work, but
to respond to your last paragraph on static boundary
conditions:</div>
<div>you can set xl_boundary_type (etc.) in flash.par to
"user" and </div>
<div>you can modify Grid_bcApplyToRegionSpecialized.F90
"case(USER_DEFINED)" to set variables to a constant value.<br
clear="all">
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<div>Best,</div>
<div dir="ltr">--------
<div>Ryan</div>
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<div dir="ltr" class="gmail_attr">On Tue, Oct 29, 2019 at
11:59 AM guido <<a href="mailto:g.granda@irya.unam.mx"
target="_blank" moz-do-not-send="true">g.granda@irya.unam.mx</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hi Flash users,<br>
<br>
I've been trying to find out how boundary cells properties
are filled <br>
when periodic boundary conditions are used. Do you know if
these cells' <br>
properties like<br>
<br>
magnetic field, velocity, etc, are filled when periodic
boundary <br>
conditions are used. Let's say our initial condition has
uniform <br>
magnetic field or uniform density,<br>
<br>
does boundary cells have the same value of these
properties or these are <br>
set to zero or sth else ?<br>
<br>
Could you please give me a hint of how to set static
boundary conditions <br>
for a simulation, e.g. a constant magnetic field at the
computational <br>
volume boundary edges.<br>
<br>
Cheers,<br>
<br>
<br>
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<div>Eddie Hansen, PhD<br>
Postdoctoral Scholar</div>
<div>University of Chicago</div>
<div>607-341-6126 | Flash Center</div>
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